From 1ebb7044c9142c67d1d2b04d84010b4810a43fd8 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 10 Jan 2012 15:08:28 -0800
Subject: [PATCH] mempool: fix first round failure behavior
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>
---
mm/mempool.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/mm/mempool.c b/mm/mempool.c
index e3a802a0cea09..d9049811f3521 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -221,14 +221,23 @@ void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
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)) {
spin_unlock_irqrestore(&pool->lock, flags);
return NULL;
}
/* Let's wait for someone else to return an element to @pool */
- gfp_temp = gfp_mask;
init_wait(&wait);
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
--
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