Messages in this thread | | | Date | Fri, 6 Jan 2012 09:37:36 -0800 (PST) | From | David Rientjes <> | Subject | Re: Switch per cpu partial page support off for debugging |
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On Wed, 14 Dec 2011, David Rientjes wrote:
> > > Eric saw an issue with accounting of slabs during validation. Its not > > > possible to determine accurately how many per cpu partial slabs exist at > > > any time so this switches off per cpu partial pages during debug. > > > > > > Subject: Switch per cpu partial page support off for debugging > > > > > > Otherwise we have accounting issues. > > > > > > Signed-off-by: Christoph Lameter <cl@linux.com> > > > > > > > > > --- > > > mm/slub.c | 4 +++- > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > Index: linux-2.6/mm/slub.c > > > =================================================================== > > > --- linux-2.6.orig/mm/slub.c 2011-11-22 11:57:21.000000000 -0600 > > > +++ linux-2.6/mm/slub.c 2011-11-22 11:57:55.000000000 -0600 > > > @@ -3027,7 +3027,9 @@ static int kmem_cache_open(struct kmem_c > > > * per node list when we run out of per cpu objects. We only fetch > > > 50% > > > * to keep some capacity around for frees. > > > */ > > > - if (s->size >= PAGE_SIZE) > > > + if (kmem_cache_debug(s)) > > > + s->cpu_partial = 0; > > > + else if (s->size >= PAGE_SIZE) > > > s->cpu_partial = 2; > > > else if (s->size >= 1024) > > > s->cpu_partial = 6; > > I think this deserves a comment since it's not clear why it's being done > neither in the code or by the changelog. Also, you'd want a check for > kmem_cache_debug() when storing to /sys/kernel/slab/cache/cpu_partial as > well, otherwise this could easily be broken from userspace again. (It > also seems like Documentation/ABI/testing/sysfs-kernel-slab got left out > of an update when that was added, too.) >
This patch is merged in slab/urgent without any changes from my comment above; since userspace can alter cpu_partial directly via /sys/kernel/slab/cache/cpu_partial which would reintroduce the "accounting issues", shouldn't that return -EINVAL when debug is enabled?
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