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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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tracing: Create a sparse bitmask for pid filtering
When the trace_pid_list was created, the default pid max was 32768. Creating a bitmask that can hold one bit for all 32768 took up 4096 (one page). Having a one page bitmask was not much of a problem, and that was used for mapping pids. But today, systems are bigger and can run more tasks, and now the default pid_max is usually set to 4194304. Which means to handle that many pids requires 524288 bytes. Worse yet, the pid_max can be set to 2^30 (1073741824 or 1G) which would take 134217728 (128M) of memory to store this array. Since the pid_list array is very sparsely populated, it is a huge waste of memory to store all possible bits for each pid when most will not be set. Instead, use a page table scheme to store the array, and allow this to handle up to 30 bit pids. The pid_mask will start out with 256 entries for the first 8 MSB bits. This will cost 1K for 32 bit architectures and 2K for 64 bit. Each of these will have a 256 array to store the next 8 bits of the pid (another 1 or 2K). These will hold an 2K byte bitmask (which will cover the LSB 14 bits or 16384 pids). When the trace_pid_list is allocated, it will have the 1/2K upper bits allocated, and then it will allocate a cache for the next upper chunks and the lower chunks (default 6 of each). Then when a bit is "set", these chunks will be pulled from the free list and added to the array. If the free list gets down to a lever (default 2), it will trigger an irqwork that will refill the cache back up. On clearing a bit, if the clear causes the bitmask to be zero, that chunk will then be placed back into the free cache for later use, keeping the need to allocate more down to a minimum. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware)
parent
6954e41526
commit
8d6e90983a
@ -2,10 +2,119 @@
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/*
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* Copyright (C) 2021 VMware Inc, Steven Rostedt <rostedt@goodmis.org>
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*/
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#include <linux/vmalloc.h>
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#include <linux/spinlock.h>
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#include <linux/irq_work.h>
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#include <linux/slab.h>
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#include "trace.h"
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/* See pid_list.h for details */
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static inline union lower_chunk *get_lower_chunk(struct trace_pid_list *pid_list)
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{
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union lower_chunk *chunk;
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lockdep_assert_held(&pid_list->lock);
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if (!pid_list->lower_list)
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return NULL;
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chunk = pid_list->lower_list;
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pid_list->lower_list = chunk->next;
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pid_list->free_lower_chunks--;
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WARN_ON_ONCE(pid_list->free_lower_chunks < 0);
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chunk->next = NULL;
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/*
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* If a refill needs to happen, it can not happen here
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* as the scheduler run queue locks are held.
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*/
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if (pid_list->free_lower_chunks <= CHUNK_REALLOC)
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irq_work_queue(&pid_list->refill_irqwork);
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return chunk;
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}
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static inline union upper_chunk *get_upper_chunk(struct trace_pid_list *pid_list)
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{
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union upper_chunk *chunk;
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lockdep_assert_held(&pid_list->lock);
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if (!pid_list->upper_list)
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return NULL;
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chunk = pid_list->upper_list;
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pid_list->upper_list = chunk->next;
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pid_list->free_upper_chunks--;
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WARN_ON_ONCE(pid_list->free_upper_chunks < 0);
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chunk->next = NULL;
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/*
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* If a refill needs to happen, it can not happen here
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* as the scheduler run queue locks are held.
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*/
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if (pid_list->free_upper_chunks <= CHUNK_REALLOC)
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irq_work_queue(&pid_list->refill_irqwork);
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return chunk;
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}
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static inline void put_lower_chunk(struct trace_pid_list *pid_list,
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union lower_chunk *chunk)
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{
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lockdep_assert_held(&pid_list->lock);
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chunk->next = pid_list->lower_list;
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pid_list->lower_list = chunk;
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pid_list->free_lower_chunks++;
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}
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static inline void put_upper_chunk(struct trace_pid_list *pid_list,
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union upper_chunk *chunk)
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{
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lockdep_assert_held(&pid_list->lock);
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chunk->next = pid_list->upper_list;
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pid_list->upper_list = chunk;
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pid_list->free_upper_chunks++;
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}
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static inline bool upper_empty(union upper_chunk *chunk)
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{
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/*
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* If chunk->data has no lower chunks, it will be the same
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* as a zeroed bitmask. Use find_first_bit() to test it
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* and if it doesn't find any bits set, then the array
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* is empty.
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*/
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int bit = find_first_bit((unsigned long *)chunk->data,
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sizeof(chunk->data) * 8);
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return bit >= sizeof(chunk->data) * 8;
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}
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static inline int pid_split(unsigned int pid, unsigned int *upper1,
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unsigned int *upper2, unsigned int *lower)
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{
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/* MAX_PID should cover all pids */
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BUILD_BUG_ON(MAX_PID < PID_MAX_LIMIT);
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/* In case a bad pid is passed in, then fail */
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if (unlikely(pid >= MAX_PID))
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return -1;
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*upper1 = (pid >> UPPER1_SHIFT) & UPPER_MASK;
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*upper2 = (pid >> UPPER2_SHIFT) & UPPER_MASK;
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*lower = pid & LOWER_MASK;
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return 0;
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}
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static inline unsigned int pid_join(unsigned int upper1,
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unsigned int upper2, unsigned int lower)
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{
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return ((upper1 & UPPER_MASK) << UPPER1_SHIFT) |
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((upper2 & UPPER_MASK) << UPPER2_SHIFT) |
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(lower & LOWER_MASK);
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}
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/**
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* trace_pid_list_is_set - test if the pid is set in the list
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* @pid_list: The pid list to test
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@ -19,14 +128,30 @@
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*/
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bool trace_pid_list_is_set(struct trace_pid_list *pid_list, unsigned int pid)
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{
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/*
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* If pid_max changed after filtered_pids was created, we
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* by default ignore all pids greater than the previous pid_max.
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*/
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if (pid >= pid_list->pid_max)
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union upper_chunk *upper_chunk;
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union lower_chunk *lower_chunk;
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unsigned long flags;
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unsigned int upper1;
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unsigned int upper2;
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unsigned int lower;
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bool ret = false;
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if (!pid_list)
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return false;
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return test_bit(pid, pid_list->pids);
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if (pid_split(pid, &upper1, &upper2, &lower) < 0)
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return false;
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raw_spin_lock_irqsave(&pid_list->lock, flags);
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upper_chunk = pid_list->upper[upper1];
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if (upper_chunk) {
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lower_chunk = upper_chunk->data[upper2];
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if (lower_chunk)
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ret = test_bit(lower, lower_chunk->data);
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}
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raw_spin_unlock_irqrestore(&pid_list->lock, flags);
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return ret;
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}
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/**
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@ -42,13 +167,44 @@ bool trace_pid_list_is_set(struct trace_pid_list *pid_list, unsigned int pid)
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*/
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int trace_pid_list_set(struct trace_pid_list *pid_list, unsigned int pid)
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{
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/* Sorry, but we don't support pid_max changing after setting */
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if (pid >= pid_list->pid_max)
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union upper_chunk *upper_chunk;
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union lower_chunk *lower_chunk;
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unsigned long flags;
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unsigned int upper1;
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unsigned int upper2;
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unsigned int lower;
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int ret;
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if (!pid_list)
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return -ENODEV;
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if (pid_split(pid, &upper1, &upper2, &lower) < 0)
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return -EINVAL;
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set_bit(pid, pid_list->pids);
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return 0;
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raw_spin_lock_irqsave(&pid_list->lock, flags);
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upper_chunk = pid_list->upper[upper1];
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if (!upper_chunk) {
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upper_chunk = get_upper_chunk(pid_list);
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if (!upper_chunk) {
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ret = -ENOMEM;
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goto out;
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}
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pid_list->upper[upper1] = upper_chunk;
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}
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lower_chunk = upper_chunk->data[upper2];
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if (!lower_chunk) {
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lower_chunk = get_lower_chunk(pid_list);
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if (!lower_chunk) {
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ret = -ENOMEM;
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goto out;
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}
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upper_chunk->data[upper2] = lower_chunk;
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}
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set_bit(lower, lower_chunk->data);
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ret = 0;
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out:
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raw_spin_unlock_irqrestore(&pid_list->lock, flags);
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return ret;
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}
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/**
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@ -64,12 +220,41 @@ int trace_pid_list_set(struct trace_pid_list *pid_list, unsigned int pid)
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*/
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int trace_pid_list_clear(struct trace_pid_list *pid_list, unsigned int pid)
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{
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/* Sorry, but we don't support pid_max changing after setting */
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if (pid >= pid_list->pid_max)
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union upper_chunk *upper_chunk;
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union lower_chunk *lower_chunk;
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unsigned long flags;
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unsigned int upper1;
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unsigned int upper2;
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unsigned int lower;
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if (!pid_list)
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return -ENODEV;
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if (pid_split(pid, &upper1, &upper2, &lower) < 0)
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return -EINVAL;
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clear_bit(pid, pid_list->pids);
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raw_spin_lock_irqsave(&pid_list->lock, flags);
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upper_chunk = pid_list->upper[upper1];
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if (!upper_chunk)
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goto out;
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lower_chunk = upper_chunk->data[upper2];
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if (!lower_chunk)
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goto out;
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clear_bit(lower, lower_chunk->data);
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/* if there's no more bits set, add it to the free list */
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if (find_first_bit(lower_chunk->data, LOWER_MAX) >= LOWER_MAX) {
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put_lower_chunk(pid_list, lower_chunk);
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upper_chunk->data[upper2] = NULL;
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if (upper_empty(upper_chunk)) {
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put_upper_chunk(pid_list, upper_chunk);
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pid_list->upper[upper1] = NULL;
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}
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}
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out:
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raw_spin_unlock_irqrestore(&pid_list->lock, flags);
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return 0;
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}
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@ -88,13 +273,45 @@ int trace_pid_list_clear(struct trace_pid_list *pid_list, unsigned int pid)
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int trace_pid_list_next(struct trace_pid_list *pid_list, unsigned int pid,
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unsigned int *next)
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{
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pid = find_next_bit(pid_list->pids, pid_list->pid_max, pid);
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union upper_chunk *upper_chunk;
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union lower_chunk *lower_chunk;
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unsigned long flags;
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unsigned int upper1;
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unsigned int upper2;
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unsigned int lower;
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if (pid < pid_list->pid_max) {
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*next = pid;
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return 0;
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if (!pid_list)
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return -ENODEV;
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if (pid_split(pid, &upper1, &upper2, &lower) < 0)
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return -EINVAL;
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raw_spin_lock_irqsave(&pid_list->lock, flags);
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for (; upper1 <= UPPER_MASK; upper1++, upper2 = 0) {
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upper_chunk = pid_list->upper[upper1];
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if (!upper_chunk)
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continue;
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for (; upper2 <= UPPER_MASK; upper2++, lower = 0) {
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lower_chunk = upper_chunk->data[upper2];
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if (!lower_chunk)
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continue;
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lower = find_next_bit(lower_chunk->data, LOWER_MAX,
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lower);
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if (lower < LOWER_MAX)
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goto found;
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}
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}
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return -1;
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found:
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raw_spin_unlock_irqrestore(&pid_list->lock, flags);
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if (upper1 > UPPER_MASK)
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return -1;
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*next = pid_join(upper1, upper2, lower);
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return 0;
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}
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/**
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@ -109,15 +326,79 @@ int trace_pid_list_next(struct trace_pid_list *pid_list, unsigned int pid,
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*/
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int trace_pid_list_first(struct trace_pid_list *pid_list, unsigned int *pid)
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{
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unsigned int first;
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return trace_pid_list_next(pid_list, 0, pid);
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}
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first = find_first_bit(pid_list->pids, pid_list->pid_max);
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static void pid_list_refill_irq(struct irq_work *iwork)
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{
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struct trace_pid_list *pid_list = container_of(iwork, struct trace_pid_list,
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refill_irqwork);
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union upper_chunk *upper;
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union lower_chunk *lower;
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union upper_chunk **upper_next = &upper;
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union lower_chunk **lower_next = &lower;
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int upper_count;
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int lower_count;
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int ucnt = 0;
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int lcnt = 0;
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if (first < pid_list->pid_max) {
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*pid = first;
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return 0;
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again:
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raw_spin_lock(&pid_list->lock);
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upper_count = CHUNK_ALLOC - pid_list->free_upper_chunks;
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lower_count = CHUNK_ALLOC - pid_list->free_lower_chunks;
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raw_spin_unlock(&pid_list->lock);
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if (upper_count <= 0 && lower_count <= 0)
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return;
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while (upper_count-- > 0) {
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union upper_chunk *chunk;
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chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
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if (!chunk)
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break;
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*upper_next = chunk;
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upper_next = &chunk->next;
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ucnt++;
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}
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return -1;
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while (lower_count-- > 0) {
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union lower_chunk *chunk;
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chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
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if (!chunk)
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break;
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*lower_next = chunk;
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lower_next = &chunk->next;
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lcnt++;
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}
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raw_spin_lock(&pid_list->lock);
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if (upper) {
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*upper_next = pid_list->upper_list;
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pid_list->upper_list = upper;
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pid_list->free_upper_chunks += ucnt;
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}
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if (lower) {
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*lower_next = pid_list->lower_list;
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pid_list->lower_list = lower;
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pid_list->free_lower_chunks += lcnt;
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}
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raw_spin_unlock(&pid_list->lock);
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/*
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* On success of allocating all the chunks, both counters
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* will be less than zero. If they are not, then an allocation
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* failed, and we should not try again.
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*/
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if (upper_count >= 0 || lower_count >= 0)
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return;
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/*
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* When the locks were released, free chunks could have
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* been used and allocation needs to be done again. Might as
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* well allocate it now.
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*/
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goto again;
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}
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/**
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@ -130,18 +411,41 @@ int trace_pid_list_first(struct trace_pid_list *pid_list, unsigned int *pid)
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struct trace_pid_list *trace_pid_list_alloc(void)
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{
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struct trace_pid_list *pid_list;
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int i;
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pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
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/* According to linux/thread.h, pids can be no bigger that 30 bits */
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WARN_ON_ONCE(pid_max > (1 << 30));
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pid_list = kzalloc(sizeof(*pid_list), GFP_KERNEL);
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if (!pid_list)
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return NULL;
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pid_list->pid_max = READ_ONCE(pid_max);
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init_irq_work(&pid_list->refill_irqwork, pid_list_refill_irq);
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pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
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if (!pid_list->pids) {
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kfree(pid_list);
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return NULL;
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raw_spin_lock_init(&pid_list->lock);
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for (i = 0; i < CHUNK_ALLOC; i++) {
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union upper_chunk *chunk;
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chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
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if (!chunk)
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break;
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chunk->next = pid_list->upper_list;
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pid_list->upper_list = chunk;
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pid_list->free_upper_chunks++;
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}
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for (i = 0; i < CHUNK_ALLOC; i++) {
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union lower_chunk *chunk;
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chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
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if (!chunk)
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break;
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chunk->next = pid_list->lower_list;
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pid_list->lower_list = chunk;
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pid_list->free_lower_chunks++;
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}
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return pid_list;
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}
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@ -152,9 +456,40 @@ struct trace_pid_list *trace_pid_list_alloc(void)
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*/
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void trace_pid_list_free(struct trace_pid_list *pid_list)
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{
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union upper_chunk *upper;
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union lower_chunk *lower;
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int i, j;
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if (!pid_list)
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return;
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vfree(pid_list->pids);
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irq_work_sync(&pid_list->refill_irqwork);
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while (pid_list->lower_list) {
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union lower_chunk *chunk;
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chunk = pid_list->lower_list;
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pid_list->lower_list = pid_list->lower_list->next;
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kfree(chunk);
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}
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while (pid_list->upper_list) {
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union upper_chunk *chunk;
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chunk = pid_list->upper_list;
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pid_list->upper_list = pid_list->upper_list->next;
|
||||
kfree(chunk);
|
||||
}
|
||||
|
||||
for (i = 0; i < UPPER1_SIZE; i++) {
|
||||
upper = pid_list->upper[i];
|
||||
if (upper) {
|
||||
for (j = 0; j < UPPER2_SIZE; j++) {
|
||||
lower = upper->data[j];
|
||||
kfree(lower);
|
||||
}
|
||||
kfree(upper);
|
||||
}
|
||||
}
|
||||
kfree(pid_list);
|
||||
}
|
||||
|
||||
@ -5,9 +5,84 @@
|
||||
#ifndef _TRACE_INTERNAL_PID_LIST_H
|
||||
#define _TRACE_INTERNAL_PID_LIST_H
|
||||
|
||||
/*
|
||||
* In order to keep track of what pids to trace, a tree is created much
|
||||
* like page tables are used. This creates a sparse bit map, where
|
||||
* the tree is filled in when needed. A PID is at most 30 bits (see
|
||||
* linux/thread.h), and is broken up into 3 sections based on the bit map
|
||||
* of the bits. The 8 MSB is the "upper1" section. The next 8 MSB is the
|
||||
* "upper2" section and the 14 LSB is the "lower" section.
|
||||
*
|
||||
* A trace_pid_list structure holds the "upper1" section, in an
|
||||
* array of 256 pointers (1 or 2K in size) to "upper_chunk" unions, where
|
||||
* each has an array of 256 pointers (1 or 2K in size) to the "lower_chunk"
|
||||
* structures, where each has an array of size 2K bytes representing a bitmask
|
||||
* of the 14 LSB of the PID (256 * 8 = 2048)
|
||||
*
|
||||
* When a trace_pid_list is allocated, it includes the 256 pointer array
|
||||
* of the upper1 unions. Then a "cache" of upper and lower is allocated
|
||||
* where these will be assigned as needed.
|
||||
*
|
||||
* When a bit is set in the pid_list bitmask, the pid to use has
|
||||
* the 8 MSB masked, and this is used to index the array in the
|
||||
* pid_list to find the next upper union. If the element is NULL,
|
||||
* then one is retrieved from the upper_list cache. If none is
|
||||
* available, then -ENOMEM is returned.
|
||||
*
|
||||
* The next 8 MSB is used to index into the "upper2" section. If this
|
||||
* element is NULL, then it is retrieved from the lower_list cache.
|
||||
* Again, if one is not available -ENOMEM is returned.
|
||||
*
|
||||
* Finally the 14 LSB of the PID is used to set the bit in the 16384
|
||||
* bitmask (made up of 2K bytes).
|
||||
*
|
||||
* When the second upper section or the lower section has their last
|
||||
* bit cleared, they are added back to the free list to be reused
|
||||
* when needed.
|
||||
*/
|
||||
|
||||
#define UPPER_BITS 8
|
||||
#define UPPER_MAX (1 << UPPER_BITS)
|
||||
#define UPPER1_SIZE (1 << UPPER_BITS)
|
||||
#define UPPER2_SIZE (1 << UPPER_BITS)
|
||||
|
||||
#define LOWER_BITS 14
|
||||
#define LOWER_MAX (1 << LOWER_BITS)
|
||||
#define LOWER_SIZE (LOWER_MAX / BITS_PER_LONG)
|
||||
|
||||
#define UPPER1_SHIFT (LOWER_BITS + UPPER_BITS)
|
||||
#define UPPER2_SHIFT LOWER_BITS
|
||||
#define LOWER_MASK (LOWER_MAX - 1)
|
||||
|
||||
#define UPPER_MASK (UPPER_MAX - 1)
|
||||
|
||||
/* According to linux/thread.h pids can not be bigger than or equal to 1 << 30 */
|
||||
#define MAX_PID (1 << 30)
|
||||
|
||||
/* Just keep 6 chunks of both upper and lower in the cache on alloc */
|
||||
#define CHUNK_ALLOC 6
|
||||
|
||||
/* Have 2 chunks free, trigger a refill of the cache */
|
||||
#define CHUNK_REALLOC 2
|
||||
|
||||
union lower_chunk {
|
||||
union lower_chunk *next;
|
||||
unsigned long data[LOWER_SIZE]; // 2K in size
|
||||
};
|
||||
|
||||
union upper_chunk {
|
||||
union upper_chunk *next;
|
||||
union lower_chunk *data[UPPER2_SIZE]; // 1 or 2K in size
|
||||
};
|
||||
|
||||
struct trace_pid_list {
|
||||
int pid_max;
|
||||
unsigned long *pids;
|
||||
raw_spinlock_t lock;
|
||||
struct irq_work refill_irqwork;
|
||||
union upper_chunk *upper[UPPER1_SIZE]; // 1 or 2K in size
|
||||
union upper_chunk *upper_list;
|
||||
union lower_chunk *lower_list;
|
||||
int free_upper_chunks;
|
||||
int free_lower_chunks;
|
||||
};
|
||||
|
||||
#endif /* _TRACE_INTERNAL_PID_LIST_H */
|
||||
|
||||
Loading…
Reference in New Issue
Block a user