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mempool: fix first round failure behavior

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mempool modifies gfp_mask so that the backing allocator doesn't try too
hard or trigger warning message when there's pool to fall back on.  In
addition, for the first try, it removes __GFP_WAIT and IO, so that it
doesn't trigger reclaim or wait when allocation can be fulfilled from
pool; however, when that allocation fails and pool is empty too, it waits
for the pool to be replenished before retrying.

Allocation which could have succeeded after a bit of reclaim has to wait
on the reserved items and it's not like mempool doesn't retry with
__GFP_WAIT and IO.  It just does that *after* someone returns an element,
pointlessly delaying things.

Fix it by retrying immediately if the first round of allocation attempts
w/o __GFP_WAIT and IO fails.

[akpm@linux-foundation.org: shorten the lock hold time]
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tejun Heo 2012-01-10 15:08:28 -08:00 committed by Linus Torvalds
parent 0565d31776
commit 1ebb7044c9
1 changed files with 11 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

13
mm/mempool.c
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@ -221,14 +221,23 @@ void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
return element; return element;
} }
/* We must not sleep in the GFP_ATOMIC case */ /*
* We use gfp mask w/o __GFP_WAIT or IO for the first round. If
* alloc failed with that and @pool was empty, retry immediately.
*/
if (gfp_temp != gfp_mask) {
spin_unlock_irqrestore(&pool->lock, flags);
gfp_temp = gfp_mask;
goto repeat_alloc;
}
/* We must not sleep if !__GFP_WAIT */
if (!(gfp_mask & __GFP_WAIT)) { if (!(gfp_mask & __GFP_WAIT)) {
spin_unlock_irqrestore(&pool->lock, flags); spin_unlock_irqrestore(&pool->lock, flags);
return NULL; return NULL;
} }
/* Let's wait for someone else to return an element to @pool */ /* Let's wait for someone else to return an element to @pool */
gfp_temp = gfp_mask;
init_wait(&wait); init_wait(&wait);
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);