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blk-wbt: throttle discards like background writes

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Throttle discards like we would any background write. Discards should
be background activity, so if they are impacting foreground IO, then
we will throttle them down.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-05-07 10:03:23 -06:00
parent 8bea609019
commit 782f569774
3 changed files with 32 additions and 21 deletions
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6
block/blk-stat.h
View File

@ -10,11 +10,11 @@
/*
* from upper:
* 3 bits: reserved for other usage
* 4 bits: reserved for other usage
* 12 bits: size
* 49 bits: time
* 48 bits: time
*/
#define BLK_STAT_RES_BITS 3
#define BLK_STAT_RES_BITS 4
#define BLK_STAT_SIZE_BITS 12
#define BLK_STAT_RES_SHIFT (64 - BLK_STAT_RES_BITS)
#define BLK_STAT_SIZE_SHIFT (BLK_STAT_RES_SHIFT - BLK_STAT_SIZE_BITS)

43
block/blk-wbt.c
View File

@ -106,6 +106,8 @@ static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb,
{
if (wb_acct & WBT_KSWAPD)
return &rwb->rq_wait[WBT_RWQ_KSWAPD];
else if (wb_acct & WBT_DISCARD)
return &rwb->rq_wait[WBT_RWQ_DISCARD];
return &rwb->rq_wait[WBT_RWQ_BG];
}
@ -143,10 +145,13 @@ void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct)
}
/*
* If the device does write back caching, drop further down
* before we wake people up.
* For discards, our limit is always the background. For writes, if
* the device does write back caching, drop further down before we
* wake people up.
*/
if (rwb->wc && !wb_recent_wait(rwb))
if (wb_acct & WBT_DISCARD)
limit = rwb->wb_background;
else if (rwb->wc && !wb_recent_wait(rwb))
limit = 0;
else
limit = rwb->wb_normal;
@ -483,6 +488,9 @@ static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
{
unsigned int limit;
if ((rw & REQ_OP_MASK) == REQ_OP_DISCARD)
return rwb->wb_background;
/*
* At this point we know it's a buffered write. If this is
* kswapd trying to free memory, or REQ_SYNC is set, then
@ -564,21 +572,20 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
{
const int op = bio_op(bio);
/*
* If not a WRITE, do nothing
*/
if (op != REQ_OP_WRITE)
switch (bio_op(bio)) {
case REQ_OP_WRITE:
/*
* Don't throttle WRITE_ODIRECT
*/
if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) ==
(REQ_SYNC | REQ_IDLE))
return false;
/* fallthrough */
case REQ_OP_DISCARD:
return true;
default:
return false;
/*
* Don't throttle WRITE_ODIRECT
*/
if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE))
return false;
return true;
}
}
/*
@ -605,6 +612,8 @@ enum wbt_flags wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock)
if (current_is_kswapd())
ret |= WBT_KSWAPD;
if (bio_op(bio) == REQ_OP_DISCARD)
ret |= WBT_DISCARD;
__wbt_wait(rwb, ret, bio->bi_opf, lock);

4
block/blk-wbt.h
View File

@ -14,13 +14,15 @@ enum wbt_flags {
WBT_TRACKED = 1, /* write, tracked for throttling */
WBT_READ = 2, /* read */
WBT_KSWAPD = 4, /* write, from kswapd */
WBT_DISCARD = 8, /* discard */
WBT_NR_BITS = 3, /* number of bits */
WBT_NR_BITS = 4, /* number of bits */
};
enum {
WBT_RWQ_BG = 0,
WBT_RWQ_KSWAPD,
WBT_RWQ_DISCARD,
WBT_NUM_RWQ,
};