From: Rik van Riel <riel@redhat.com>
To: Andi Kleen <andi@firstfloor.org>, Alex Thorlton <athorlton@sgi.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Bob Liu <lliubbo@gmail.com>, David Rientjes <rientjes@google.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@redhat.com>,
Kees Cook <keescook@chromium.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Mel Gorman <mgorman@suse.de>, Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vladimir Davydov <vdavydov@parallels.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] Convert khugepaged to a task_work function
Date: Tue, 28 Oct 2014 08:58:42 -0400 [thread overview]
Message-ID: <544F9302.4010001@redhat.com> (raw)
In-Reply-To: <87lho0pf4l.fsf@tassilo.jf.intel.com>
On 10/28/2014 08:12 AM, Andi Kleen wrote:
> Alex Thorlton <athorlton@sgi.com> writes:
>
>> Last week, while discussing possible fixes for some unexpected/unwanted behavior
>> from khugepaged (see: https://lkml.org/lkml/2014/10/8/515) several people
>> mentioned possibly changing changing khugepaged to work as a task_work function
>> instead of a kernel thread. This will give us finer grained control over the
>> page collapse scans, eliminate some unnecessary scans since tasks that are
>> relatively inactive will not be scanned often, and eliminate the unwanted
>> behavior described in the email thread I mentioned.
>
> With your change, what would happen in a single threaded case?
>
> Previously one core would scan and another would run the workload.
> With your change both scanning and running would be on the same
> core.
>
> Would seem like a step backwards to me.
It's not just scanning, either.
Memory compaction can spend a lot of time waiting on
locks. Not consuming CPU or anything, but just waiting.
I am not convinced that moving all that waiting to task
context is a good idea.
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next prev parent reply other threads:[~2014-10-28 13:02 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-23 2:49 [PATCH 0/4] Convert khugepaged to a task_work function Alex Thorlton
2014-10-23 2:49 ` [PATCH 1/4] Disable khugepaged thread Alex Thorlton
2014-10-23 2:49 ` [PATCH] Add pgcollapse controls to task_struct Alex Thorlton
2014-10-23 15:29 ` Alex Thorlton
2014-10-23 2:49 ` [PATCH 3/4] Convert khugepaged scan functions to work with task_work Alex Thorlton
2014-10-23 2:49 ` [PATCH 4/4] Add /proc files to expose per-mm pgcollapse stats Alex Thorlton
2014-10-23 3:06 ` [PATCH 1/2] Add pgcollapse stat counter to task_struct Alex Thorlton
2014-10-23 3:06 ` [PATCH 2/2] Add /proc files to expose per-mm pgcollapse stats Alex Thorlton
2014-10-23 17:55 ` [PATCH 0/4] Convert khugepaged to a task_work function Rik van Riel
2014-10-23 18:05 ` Alex Thorlton
2014-10-23 18:52 ` Alex Thorlton
2014-10-28 12:12 ` Andi Kleen
2014-10-28 12:58 ` Rik van Riel [this message]
2014-10-28 15:39 ` Rik van Riel
2014-10-31 20:27 ` Vlastimil Babka
2014-11-17 21:34 ` Alex Thorlton
2014-11-10 11:03 ` Mel Gorman
2014-11-17 21:16 ` Alex Thorlton
2014-10-29 21:58 ` Alex Thorlton
2014-10-30 0:23 ` Kirill A. Shutemov
2014-10-30 8:35 ` Andi Kleen
2014-10-30 18:25 ` Alex Thorlton
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