diff options
author | Nick Piggin <nickpiggin@yahoo.com.au> | 2005-05-01 11:58:37 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-05-01 11:58:37 -0400 |
commit | 20a77776c24800d1e40a73f520cfcb32239568a9 (patch) | |
tree | 8a28cc68cf10b87d35b7603b2d6f26215390cc0f | |
parent | b84a35be0285229b0a8a5e2e04d79360c5b75562 (diff) |
[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>
-rw-r--r-- | mm/mempool.c | 30 |
1 files changed, 9 insertions, 21 deletions
diff --git a/mm/mempool.c b/mm/mempool.c index d691b5cb8022..e9a0a6337b21 100644 --- a/mm/mempool.c +++ b/mm/mempool.c | |||
@@ -198,36 +198,22 @@ void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask) | |||
198 | void *element; | 198 | void *element; |
199 | unsigned long flags; | 199 | unsigned long flags; |
200 | DEFINE_WAIT(wait); | 200 | DEFINE_WAIT(wait); |
201 | int gfp_nowait; | 201 | int gfp_temp; |
202 | |||
203 | might_sleep_if(gfp_mask & __GFP_WAIT); | ||
202 | 204 | ||
203 | gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */ | 205 | gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */ |
204 | gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */ | 206 | gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */ |
205 | gfp_mask |= __GFP_NOWARN; /* failures are OK */ | 207 | gfp_mask |= __GFP_NOWARN; /* failures are OK */ |
206 | gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO); | ||
207 | 208 | ||
208 | might_sleep_if(gfp_mask & __GFP_WAIT); | 209 | gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO); |
210 | |||
209 | repeat_alloc: | 211 | repeat_alloc: |
210 | element = pool->alloc(gfp_nowait, pool->pool_data); | 212 | |
213 | element = pool->alloc(gfp_temp, pool->pool_data); | ||
211 | if (likely(element != NULL)) | 214 | if (likely(element != NULL)) |
212 | return element; | 215 | return element; |
213 | 216 | ||
214 | /* | ||
215 | * If the pool is less than 50% full and we can perform effective | ||
216 | * page reclaim then try harder to allocate an element. | ||
217 | */ | ||
218 | mb(); | ||
219 | if ((gfp_mask & __GFP_FS) && (gfp_mask != gfp_nowait) && | ||
220 | (pool->curr_nr <= pool->min_nr/2)) { | ||
221 | element = pool->alloc(gfp_mask, pool->pool_data); | ||
222 | if (likely(element != NULL)) | ||
223 | return element; | ||
224 | } | ||
225 | |||
226 | /* | ||
227 | * Kick the VM at this point. | ||
228 | */ | ||
229 | wakeup_bdflush(0); | ||
230 | |||
231 | spin_lock_irqsave(&pool->lock, flags); | 217 | spin_lock_irqsave(&pool->lock, flags); |
232 | if (likely(pool->curr_nr)) { | 218 | if (likely(pool->curr_nr)) { |
233 | element = remove_element(pool); | 219 | element = remove_element(pool); |
@@ -240,6 +226,8 @@ repeat_alloc: | |||
240 | if (!(gfp_mask & __GFP_WAIT)) | 226 | if (!(gfp_mask & __GFP_WAIT)) |
241 | return NULL; | 227 | return NULL; |
242 | 228 | ||
229 | /* Now start performing page reclaim */ | ||
230 | gfp_temp = gfp_mask; | ||
243 | prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); | 231 | prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); |
244 | mb(); | 232 | mb(); |
245 | if (!pool->curr_nr) | 233 | if (!pool->curr_nr) |