[PATCH 12/19] Calculate the alloc_flags for allocation only once

Mel Gorman
2009-02-24T12:21:32Z

Factor out the mapping between GFP and alloc_flags only once. Once factored
out, it only needs to be calculated once but some care must be taken.

[neilb@suse.de says]
As the test:

- if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
- && !in_interrupt()) {
- if (!(gfp_mask & __GFP_NOMEMALLOC)) {

has been replaced with a slightly weaker one:

+ if (alloc_flags & ALLOC_NO_WATERMARKS) {

we need to ensure we don't recurse when PF_MEMALLOC is set.

From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
mm/page_alloc.c | 90 +++++++++++++++++++++++++++++++-----------------------
1 files changed, 52 insertions(+), 38 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8437291..ead73fd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1588,16 +1588,6 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
return page;
}

-static inline int is_allocation_high_priority(struct task_struct *p,
- gfp_t gfp_mask)
-{
- if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
- && !in_interrupt())
- if (!(gfp_mask & __GFP_NOMEMALLOC))
- return 1;
- return 0;
-}
-
/*
* This is called in the allocator slow-path if the allocation request is of
* sufficient urgency to ignore watermarks and take other desperate measures
@@ -1632,6 +1622,44 @@ void wake_all_kswapd(unsigned int order, struct zonelist *zonelist, enum zone_ty
wakeup_kswapd(zone, order);
}

+/*
+ * get the deepest reaching allocation flags for the given gfp_mask
+ */
+static int gfp_to_alloc_flags(gfp_t gfp_mask)
+{
+ struct task_struct *p = current;
+ int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
+ const gfp_t wait = gfp_mask & __GFP_WAIT;
+
+ /*
+ * The caller may dip into page reserves a bit more if the caller
+ * cannot run direct reclaim, or if the caller has realtime scheduling
+ * policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
+ * set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH).
+ */
+ if (gfp_mask & __GFP_HIGH)
+ alloc_flags |= ALLOC_HIGH;
+
+ if (!wait) {
+ alloc_flags |= ALLOC_HARDER;
+ /*
+ * Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
+ * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
+ */
+ alloc_flags &= ~ALLOC_CPUSET;
+ } else if (unlikely(rt_task(p)) && !in_interrupt())
+ alloc_flags |= ALLOC_HARDER;
+
+ if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
+ if (!in_interrupt() &&
+ ((p->flags & PF_MEMALLOC) ||
+ unlikely(test_thread_flag(TIF_MEMDIE))))
+ alloc_flags |= ALLOC_NO_WATERMARKS;
+ }
+
+ return alloc_flags;
+}
+
static struct page * noinline
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
@@ -1662,48 +1690,34 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
* 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 caller may dip into page reserves a bit more if the caller
- * cannot run direct reclaim, or if the caller has realtime scheduling
- * policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
- * set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH).
*/
- alloc_flags = ALLOC_WMARK_MIN;
- if ((unlikely(rt_task(p)) && !in_interrupt()) || !wait)
- alloc_flags |= ALLOC_HARDER;
- if (gfp_mask & __GFP_HIGH)
- alloc_flags |= ALLOC_HIGH;
- if (wait)
- alloc_flags |= ALLOC_CPUSET;
+ alloc_flags = gfp_to_alloc_flags(gfp_mask);

restart:
- /*
- * Go through the zonelist again. Let __GFP_HIGH and allocations
- * coming from realtime tasks go deeper into reserves.
- *
- * This is the last chance, in general, before the goto nopage.
- * Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
- * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
- */
+ /* This is the last chance, in general, before the goto nopage. */
page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
- high_zoneidx, alloc_flags,
- preferred_zone,
- migratetype);
+ high_zoneidx, alloc_flags & ~ALLOC_NO_WATERMARKS,
+ preferred_zone, migratetype);
if (page)
goto got_pg;

/* Allocate without watermarks if the context allows */
- if (is_allocation_high_priority(p, gfp_mask))
+ if (alloc_flags & ALLOC_NO_WATERMARKS) {
page = __alloc_pages_high_priority(gfp_mask, order,
- zonelist, high_zoneidx, nodemask, preferred_zone,
- migratetype);
- if (page)
- goto got_pg;
+ zonelist, high_zoneidx, nodemask,
+ preferred_zone, migratetype);
+ if (page)
+ goto got_pg;
+ }

/* Atomic allocations - we can't balance anything */
if (!wait)
goto nopage;

+ /* Avoid recursion of direct reclaim */
+ if (p->flags & PF_MEMALLOC)
+ goto nopage;
+
/* Try direct reclaim and then allocating */
page = __alloc_pages_direct_reclaim(gfp_mask, order,
zonelist, high_zoneidx,
--
1.5.6.5