In __alloc_pages_slowpath(), alloc_flags doesn't change after it's initialized,
so move the initialization above the retry: label. Also make the comment above
the initialization more descriptive.
The only exception in the alloc_flags being constant is ALLOC_NO_WATERMARKS,
which may change due to TIF_MEMDIE being set on the allocating thread. We can
fix this, and make the code simpler and a bit more effective at the same time,
by moving the part that determines ALLOC_NO_WATERMARKS from
gfp_to_alloc_flags() to gfp_pfmemalloc_allowed(). This means we don't have to
mask out ALLOC_NO_WATERMARKS in numerous places in __alloc_pages_slowpath()
anymore. The only test for the flag can instead call gfp_pfmemalloc_allowed().
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
Acked-by: Michal Hocko <mho...@suse.com>
---
mm/page_alloc.c | 49 ++++++++++++++++++++++++-------------------------
1 file changed, 24 insertions(+), 25 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f8f3bfc435ee..da3a62a94b4a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3203,8 +3203,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int
order,
*/
count_vm_event(COMPACTSTALL);
- page = get_page_from_freelist(gfp_mask, order,
- alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
+ page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
if (page) {
struct zone *zone = page_zone(page);
@@ -3372,8 +3371,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int
order,
return NULL;
retry:
- page = get_page_from_freelist(gfp_mask, order,
- alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
+ page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
/*
* If an allocation failed after direct reclaim, it could be because
@@ -3431,16 +3429,6 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
} else if (unlikely(rt_task(current)) && !in_interrupt())
alloc_flags |= ALLOC_HARDER;
- if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
- if (gfp_mask & __GFP_MEMALLOC)
- alloc_flags |= ALLOC_NO_WATERMARKS;
- else if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
- alloc_flags |= ALLOC_NO_WATERMARKS;
- else if (!in_interrupt() &&
- ((current->flags & PF_MEMALLOC) ||
- unlikely(test_thread_flag(TIF_MEMDIE))))
- alloc_flags |= ALLOC_NO_WATERMARKS;
- }
#ifdef CONFIG_CMA
if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
alloc_flags |= ALLOC_CMA;
@@ -3450,7 +3438,19 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
{
- return !!(gfp_to_alloc_flags(gfp_mask) & ALLOC_NO_WATERMARKS);
+ if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
+ return false;
+
+ if (gfp_mask & __GFP_MEMALLOC)
+ return true;
+ if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
+ return true;
+ if (!in_interrupt() &&
+ ((current->flags & PF_MEMALLOC) ||
+ unlikely(test_thread_flag(TIF_MEMDIE))))
+ return true;
+
+ return false;
}
static inline bool is_thp_gfp_mask(gfp_t gfp_mask)
@@ -3585,25 +3585,24 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int
order,
(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
gfp_mask &= ~__GFP_ATOMIC;
-retry:
- if (gfp_mask & __GFP_KSWAPD_RECLAIM)
- wake_all_kswapds(order, ac);
-
/*
- * OK, we're below the kswapd watermark and have kicked background
- * reclaim. Now things get more complex, so set up alloc_flags according
- * to how we want to proceed.
+ * The fast path uses conservative alloc_flags to succeed only until
+ * kswapd needs to be woken up, and to avoid the cost of setting up
+ * alloc_flags precisely. So we do that now.
*/
alloc_flags = gfp_to_alloc_flags(gfp_mask);
+retry:
+ if (gfp_mask & __GFP_KSWAPD_RECLAIM)
+ wake_all_kswapds(order, ac);
+
/* This is the last chance, in general, before the goto nopage. */
- page = get_page_from_freelist(gfp_mask, order,
- alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
+ page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
if (page)
goto got_pg;
/* Allocate without watermarks if the context allows */
- if (alloc_flags & ALLOC_NO_WATERMARKS) {
+ if (gfp_pfmemalloc_allowed(gfp_mask)) {
/*
* Ignore mempolicies if ALLOC_NO_WATERMARKS on the grounds
* the allocation is high priority and these type of
--
2.8.3
