lkml.org 
[lkml]   [2014]   [Jan]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
On Wed, 8 Jan 2014, David Rientjes wrote:

> > There used to be only one path out of __slab_alloc(), and
> > ALLOC_SLOWPATH got bumped in that exit path. Now there are two,
> > and a bunch of gotos. ALLOC_SLOWPATH can now get set more than once
> > during a single call to __slab_alloc() which is pretty bogus.
> > Here's the sequence:
> >
> > 1. Enter __slab_alloc(), fall through all the way to the
> > stat(s, ALLOC_SLOWPATH);
> > 2. hit 'if (!freelist)', and bump DEACTIVATE_BYPASS, jump to
> > new_slab (goto #1)
> > 3. Hit 'if (c->partial)', bump CPU_PARTIAL_ALLOC, goto redo
> > (goto #2)
> > 4. Fall through in the same path we did before all the way to
> > stat(s, ALLOC_SLOWPATH)
> > 5. bump ALLOC_REFILL stat, then return
> >
> > Doing this is obviously bogus. It keeps us from being able to
> > accurately compare ALLOC_SLOWPATH vs. ALLOC_FASTPATH. It also
> > means that the total number of allocs always exceeds the total
> > number of frees.
> >
> > This patch moves stat(s, ALLOC_SLOWPATH) to be called from the
> > same place that __slab_alloc() is. This makes it much less
> > likely that ALLOC_SLOWPATH will get botched again in the
> > spaghetti-code inside __slab_alloc().
> >
> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
>
> Acked-by: David Rientjes <rientjes@google.com>
>

Pekka, are you going to pick this up for linux-next? I think it would be
nice to have for 3.14 for those of us who use the stats.


\
 
 \ /
  Last update: 2014-01-22 00:01    [W:0.138 / U:2.924 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site