From: Johannes Weiner <hannes@cmpxchg.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Hansen <dave@sr71.net>, Michal Hocko <mhocko@suse.com>,
Hugh Dickins <hughd@google.com>, Tejun Heo <tj@kernel.org>,
Vladimir Davydov <vdavydov@parallels.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: regression caused by cgroups optimization in 3.17-rc2
Date: Tue, 2 Sep 2014 21:33:17 -0400 [thread overview]
Message-ID: <20140903013317.GA26086@cmpxchg.org> (raw)
In-Reply-To: <CA+55aFw6ZkGNVX-CwyG0ybQAPjYAscdM59k_tOLtg4rr-fS-jg@mail.gmail.com>
On Tue, Sep 02, 2014 at 05:20:55PM -0700, Linus Torvalds wrote:
> On Tue, Sep 2, 2014 at 5:10 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> >
> > That looks like a partial profile, where did the page allocator, page
> > zeroing etc. go? Because the distribution among these listed symbols
> > doesn't seem all that crazy:
>
> Please argue this *after* the commit has been reverted. You guys can
> try to make the memcontrol batching actually work and scale later.
> It's not appropriate to argue against major regressions when reported
> and bisected by users.
I'll send a clean revert later.
> Showing the spinlock at the top of the profile is very much crazy
> (apparently taking 68% of all cpu time), when it's all useless
> make-believe work. I don't understand why you wouldn't call that
> crazy.
If you limit perf to a subset of symbols, it will show a relative
distribution between them, i.e: perf top --symbols kfree,memset during
some disk access:
PerfTop: 1292 irqs/sec kernel:84.4% exact: 0.0% [4000Hz cycles], (all, 4 CPUs)
-------------------------------------------------------------------------------
56.23% [kernel] [k] kfree
41.86% [kernel] [k] memset
1.91% libc-2.19.so [.] memset
kfree isn't eating 56% of "all cpu time" here, and it wasn't clear to
me whether Dave filtered symbols from only memcontrol.o, memory.o, and
mmap.o in a similar way. I'm not arguing against the regression, I'm
just trying to make sense of the numbers from the *patched* kernel.
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next prev parent reply other threads:[~2014-09-03 1:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 19:05 Dave Hansen
2014-09-02 20:18 ` Dave Hansen
2014-09-02 20:57 ` Dave Hansen
2014-09-04 14:27 ` Michal Hocko
2014-09-04 20:27 ` Dave Hansen
2014-09-04 22:53 ` Dave Hansen
2014-09-05 9:28 ` Michal Hocko
2014-09-05 9:25 ` Michal Hocko
2014-09-05 14:47 ` Johannes Weiner
2014-09-05 15:39 ` Michal Hocko
2014-09-10 16:29 ` Michal Hocko
2014-09-10 16:57 ` Dave Hansen
2014-09-10 17:05 ` Michal Hocko
2014-09-05 12:35 ` Johannes Weiner
2014-09-08 15:47 ` Dave Hansen
2014-09-09 14:50 ` Johannes Weiner
2014-09-09 18:23 ` Dave Hansen
2014-09-02 22:18 ` Johannes Weiner
2014-09-02 22:36 ` Dave Hansen
2014-09-03 0:10 ` Johannes Weiner
2014-09-03 0:20 ` Linus Torvalds
2014-09-03 1:33 ` Johannes Weiner [this message]
2014-09-03 3:15 ` Dave Hansen
2014-09-03 0:30 ` Dave Hansen
2014-09-04 15:08 ` Johannes Weiner
2014-09-04 20:50 ` Dave Hansen
2014-09-05 8:04 ` Michal Hocko
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