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authorNick Piggin <nickpiggin@yahoo.com.au>2005-05-01 08:58:37 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-01 08:58:37 -0700
commit20a77776c24800d1e40a73f520cfcb32239568a9 (patch)
tree8a28cc68cf10b87d35b7603b2d6f26215390cc0f /mm
parentb84a35be0285229b0a8a5e2e04d79360c5b75562 (diff)
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[PATCH] mempool: simplify alloc
Mempool is pretty clever. Looks too clever for its own good :) It shouldn't really know so much about page reclaim internals. - don't guess about what effective page reclaim might involve. - don't randomly flush out all dirty data if some unlikely thing happens (alloc returns NULL). page reclaim can (sort of :P) handle it. I think the main motivation is trying to avoid pool->lock at all costs. However the first allocation is attempted with __GFP_WAIT cleared, so it will be 'can_try_harder' if it hits the page allocator. So if allocation still fails, then we can probably afford to hit the pool->lock - and what's the alternative? Try page reclaim and hit zone->lru_lock? A nice upshot is that we don't need to do any fancy memory barriers or do (intentionally) racy access to pool-> fields outside the lock. Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mempool.c30
1 files changed, 9 insertions, 21 deletions
diff --git a/mm/mempool.c b/mm/mempool.c
index d691b5cb802..e9a0a6337b2 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -198,36 +198,22 @@ void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask)
void *element;
unsigned long flags;
DEFINE_WAIT(wait);
- int gfp_nowait;
+ int gfp_temp;
+
+ might_sleep_if(gfp_mask & __GFP_WAIT);
gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
gfp_mask |= __GFP_NOWARN; /* failures are OK */
- gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
- might_sleep_if(gfp_mask & __GFP_WAIT);
+ gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
+
repeat_alloc:
- element = pool->alloc(gfp_nowait, pool->pool_data);
+
+ element = pool->alloc(gfp_temp, pool->pool_data);
if (likely(element != NULL))
return element;
- /*
- * If the pool is less than 50% full and we can perform effective
- * page reclaim then try harder to allocate an element.
- */
- mb();
- if ((gfp_mask & __GFP_FS) && (gfp_mask != gfp_nowait) &&
- (pool->curr_nr <= pool->min_nr/2)) {
- element = pool->alloc(gfp_mask, pool->pool_data);
- if (likely(element != NULL))
- return element;
- }
-
- /*
- * Kick the VM at this point.
- */
- wakeup_bdflush(0);
-
spin_lock_irqsave(&pool->lock, flags);
if (likely(pool->curr_nr)) {
element = remove_element(pool);
@@ -240,6 +226,8 @@ repeat_alloc:
if (!(gfp_mask & __GFP_WAIT))
return NULL;
+ /* Now start performing page reclaim */
+ gfp_temp = gfp_mask;
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
mb();
if (!pool->curr_nr)