On Mon, 20 Aug 2012 10:02:05 -0700 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Aug 20, 2012 at 2:04 AM, Mel Gorman <mgorman@xxxxxxx> wrote:
> >
> > Can the following patch be tested please? It is reported to fix an fio
> > regression that may be similar to what you are experiencing but has not
> > been picked up yet.
>
> Andrew, is this in your queue, or should I take this directly, or
> what? It seems to fix the problem for Eric and Sage, at least.
Yes, I have a copy queued:
From: Alex Shi <alex.shi@xxxxxxxxx>
Subject: mm: correct page->pfmemalloc to fix deactivate_slab regression
cfd19c5a9ec ("mm: only set page->pfmemalloc when ALLOC_NO_WATERMARKS was
used") tried to narrow down page->pfmemalloc setting, but it missed some
places the pfmemalloc should be set.
So, in __slab_alloc, the unalignment pfmemalloc and ALLOC_NO_WATERMARKS
cause incorrect deactivate_slab() on our core2 server:
64.73% fio [kernel.kallsyms] [k] _raw_spin_lock
|
--- _raw_spin_lock
|
|---0.34%-- deactivate_slab
| __slab_alloc
| kmem_cache_alloc
| |
That causes our fio sync write performance to have a 40% regression.
Move the checking in get_page_from_freelist() which resolves this issue.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Tested-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Tested-by: Sage Weil <sage@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff -puN mm/page_alloc.c~mm-correct-page-pfmemalloc-to-fix-deactivate_slab-regression mm/page_alloc.c
--- a/mm/page_alloc.c~mm-correct-page-pfmemalloc-to-fix-deactivate_slab-regression
+++ a/mm/page_alloc.c
@@ -1928,6 +1928,17 @@ this_zone_full:
zlc_active = 0;
goto zonelist_scan;
}
+
+ if (page)
+ /*
+ * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
+ * necessary to allocate the page. The expectation is
+ * that the caller is taking steps that will free more
+ * memory. The caller should avoid the page being used
+ * for !PFMEMALLOC purposes.
+ */
+ page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS);
+
return page;
}
@@ -2389,14 +2400,6 @@ rebalance:
zonelist, high_zoneidx, nodemask,
preferred_zone, migratetype);
if (page) {
- /*
- * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
- * necessary to allocate the page. The expectation is
- * that the caller is taking steps that will free more
- * memory. The caller should avoid the page being used
- * for !PFMEMALLOC purposes.
- */
- page->pfmemalloc = true;
goto got_pg;
}
}
@@ -2569,8 +2572,6 @@ retry_cpuset:
page = __alloc_pages_slowpath(gfp_mask, order,
zonelist, high_zoneidx, nodemask,
preferred_zone, migratetype);
- else
- page->pfmemalloc = false;
trace_mm_page_alloc(page, order, gfp_mask, migratetype);
_
--
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