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tracing: Have saved_cmdlines arrays all in one allocation

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[ Upstream commit 0b18c852cc ]

The saved_cmdlines have three arrays for mapping PIDs to COMMs:

 - map_pid_to_cmdline[]
 - map_cmdline_to_pid[]
 - saved_cmdlines

The map_pid_to_cmdline[] is PID_MAX_DEFAULT in size and holds the index
into the other arrays. The map_cmdline_to_pid[] is a mapping back to the
full pid as it can be larger than PID_MAX_DEFAULT. And the
saved_cmdlines[] just holds the COMMs associated to the pids.

Currently the map_pid_to_cmdline[] and saved_cmdlines[] are allocated
together (in reality the saved_cmdlines is just in the memory of the
rounding of the allocation of the structure as it is always allocated in
powers of two). The map_cmdline_to_pid[] array is allocated separately.

Since the rounding to a power of two is rather large (it allows for 8000
elements in saved_cmdlines), also include the map_cmdline_to_pid[] array.
(This drops it to 6000 by default, which is still plenty for most use
cases). This saves even more memory as the map_cmdline_to_pid[] array
doesn't need to be allocated.

Link: https://lore.kernel.org/linux-trace-kernel/20240212174011.068211d9@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20240220140703.182330529@goodmis.org

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Mete Durlu <meted@linux.ibm.com>
Fixes: 44dc5c41b5 ("tracing: Fix wasted memory in saved_cmdlines logic")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Steven Rostedt (Google) 2024-02-20 09:06:14 -05:00 committed by Greg Kroah-Hartman
parent 25b0021620
commit f2fd1a9597
1 changed files with 8 additions and 10 deletions
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18
kernel/trace/trace.c
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@ -2244,6 +2244,10 @@ struct saved_cmdlines_buffer {
};
static struct saved_cmdlines_buffer *savedcmd;
/* Holds the size of a cmdline and pid element */
#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
(TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
static inline char *get_saved_cmdlines(int idx)
{
return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
@ -2258,7 +2262,6 @@ static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
{
int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);
kfree(s->map_cmdline_to_pid);
kmemleak_free(s);
free_pages((unsigned long)s, order);
}
@ -2271,7 +2274,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
int order;
/* Figure out how much is needed to hold the given number of cmdlines */
orig_size = sizeof(*s) + val * TASK_COMM_LEN;
orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
order = get_order(orig_size);
size = 1 << (order + PAGE_SHIFT);
page = alloc_pages(GFP_KERNEL, order);
@ -2283,16 +2286,11 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
memset(s, 0, sizeof(*s));
/* Round up to actual allocation */
val = (size - sizeof(*s)) / TASK_COMM_LEN;
val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
s->cmdline_num = val;
s->map_cmdline_to_pid = kmalloc_array(val,
sizeof(*s->map_cmdline_to_pid),
GFP_KERNEL);
if (!s->map_cmdline_to_pid) {
free_saved_cmdlines_buffer(s);
return NULL;
}
/* Place map_cmdline_to_pid array right after saved_cmdlines */
s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
s->cmdline_idx = 0;
memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,