From 1ebb7044c9142c67d1d2b04d84010b4810a43fd8 Mon Sep 17 00:00:00 2001 From: Tejun Heo 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mempool.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/mm/mempool.c b/mm/mempool.c index e3a802a0cea0..d9049811f352 100644 --- a/mm/mempool.c +++ b/mm/mempool.c @@ -221,14 +221,23 @@ repeat_alloc: 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); -- 2.20.1