Re: [PATCH] mm: SLAB Out-of-memory diagnostics
From: Pekka Enberg <penberg@kernel.org>
Date: 2012-02-29 07:37:41
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On Wed, 29 Feb 2012, Rafael Aquini wrote:
Following the example at mm/slub.c, add out-of-memory diagnostics to the SLAB
allocator to help on debugging OOM conditions. This patch also adds a new
sysctl, 'oom_dump_slabs_forced', that overrides the effect of __GFP_NOWARN page
allocation flag and forces the kernel to report every slab allocation failure.
An example print out looks like this:
<snip page allocator out-of-memory message>
SLAB: Unable to allocate memory on node 0 (gfp=0x11200)
cache: bio-0, object size: 192, order: 0
node0: slabs: 3/3, objs: 60/60, free: 0
Signed-off-by: Rafael Aquini <redacted>
---
Documentation/sysctl/vm.txt | 23 ++++++++++++++++++
include/linux/slab.h | 2 +
kernel/sysctl.c | 9 +++++++
mm/slab.c | 55 ++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 88 insertions(+), 1 deletions(-)No SLUB support for this?
quoted hunk ↗ jump to hunk
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 96f0ee8..75bdf91 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt@@ -498,6 +498,29 @@ this is causing problems for your system/application. ============================================================== +oom_dump_slabs_forced + +Overrides the effects of __GFP_NOWARN page allocation flag, thus forcing +the system to print warnings about every allocation failure for the +slab allocator, and helping on debugging certain OOM conditions. +The print out is pretty similar, and complements data that is reported by +the page allocator out-of-memory warning: + +<snip page allocator out-of-memory message> + SLAB: Unable to allocate memory on node 0 (gfp=0x11200) + cache: bio-0, object size: 192, order: 0 + node0: slabs: 3/3, objs: 60/60, free: 0 + +If this is set to zero, the default behavior is observed and warnings will only +be printed out for allocation requests that didn't set the __GFP_NOWARN flag. + +When set to non-zero, this information is shown whenever the allocator finds +itself failing to grant a request, regardless the __GFP_NOWARN flag status. + +The default value is 0 (disabled). + +============================================================== +
Why do you want to add a sysctl for this? That'd be an ABI that we need to keep around forever. Is there any reason we shouldn't just enable this unconditionally? Pekka -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>