From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michael J Wolf <mjwolf@us.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC][PATCH 0/6] more detailed per-process transparent hugepage statistics
Date: Tue, 08 Feb 2011 09:54:34 -0800 [thread overview]
Message-ID: <1297187674.6737.12145.camel@nimitz> (raw)
In-Reply-To: <20110202000750.GC16981@random.random>
On Wed, 2011-02-02 at 01:07 +0100, Andrea Arcangeli wrote:
> > I guess we could also try and figure out whether the khugepaged CPU
> > overhead really comes from the scanning or the collapsing operations
> > themselves. Should be as easy as some oprofiling.
>
> Actually I already know, the scanning is super fast. So it's no real
> big deal to increase the scanning. It's big deal only if there are
> plenty more of collapse/split. Compared to the KSM scan, the
> khugepaged scan costs nothing.
Just FYI, I did some profiling on a workload that constantly split and
joined pages. Very little of the overhead was in the scanning itself,
so I think you're dead-on here.
-- Dave
WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michael J Wolf <mjwolf@us.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC][PATCH 0/6] more detailed per-process transparent hugepage statistics
Date: Tue, 08 Feb 2011 09:54:34 -0800 [thread overview]
Message-ID: <1297187674.6737.12145.camel@nimitz> (raw)
In-Reply-To: <20110202000750.GC16981@random.random>
On Wed, 2011-02-02 at 01:07 +0100, Andrea Arcangeli wrote:
> > I guess we could also try and figure out whether the khugepaged CPU
> > overhead really comes from the scanning or the collapsing operations
> > themselves. Should be as easy as some oprofiling.
>
> Actually I already know, the scanning is super fast. So it's no real
> big deal to increase the scanning. It's big deal only if there are
> plenty more of collapse/split. Compared to the KSM scan, the
> khugepaged scan costs nothing.
Just FYI, I did some profiling on a workload that constantly split and
joined pages. Very little of the overhead was in the scanning itself,
so I think you're dead-on here.
-- Dave
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next prev parent reply other threads:[~2011-02-08 17:54 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-01 0:33 [RFC][PATCH 0/6] more detailed per-process transparent hugepage statistics Dave Hansen
2011-02-01 0:33 ` Dave Hansen
2011-02-01 0:33 ` [RFC][PATCH 1/6] count transparent hugepage splits Dave Hansen
2011-02-01 0:33 ` Dave Hansen
2011-02-01 9:58 ` Johannes Weiner
2011-02-01 9:58 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:22 ` David Rientjes
2011-02-04 21:18 ` Andrea Arcangeli
2011-02-04 21:18 ` Andrea Arcangeli
2011-02-04 21:28 ` Dave Hansen
2011-02-04 21:28 ` Dave Hansen
2011-02-01 0:33 ` [RFC][PATCH 2/6] pagewalk: only split huge pages when necessary Dave Hansen
2011-02-01 0:33 ` Dave Hansen
2011-02-01 10:04 ` Johannes Weiner
2011-02-01 10:04 ` Johannes Weiner
2011-02-01 15:03 ` Dave Hansen
2011-02-01 15:03 ` Dave Hansen
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:33 ` Dave Hansen
2011-02-03 21:33 ` Dave Hansen
2011-02-03 21:46 ` David Rientjes
2011-02-03 21:46 ` David Rientjes
2011-02-04 17:19 ` Dave Hansen
2011-02-04 17:19 ` Dave Hansen
2011-02-04 21:10 ` Andrea Arcangeli
2011-02-04 21:10 ` Andrea Arcangeli
2011-02-01 0:34 ` [RFC][PATCH 3/6] break out smaps_pte_entry() from smaps_pte_range() Dave Hansen
2011-02-01 0:34 ` Dave Hansen
2011-02-01 10:08 ` Johannes Weiner
2011-02-01 10:08 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:40 ` Dave Hansen
2011-02-03 21:40 ` Dave Hansen
2011-02-01 0:34 ` [RFC][PATCH 4/6] pass pte size argument in to smaps_pte_entry() Dave Hansen
2011-02-01 0:34 ` Dave Hansen
2011-02-01 10:09 ` Johannes Weiner
2011-02-01 10:09 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:22 ` David Rientjes
2011-02-01 0:34 ` [RFC][PATCH 5/6] teach smaps_pte_range() about THP pmds Dave Hansen
2011-02-01 0:34 ` Dave Hansen
2011-02-01 10:11 ` Johannes Weiner
2011-02-01 10:11 ` Johannes Weiner
2011-02-01 15:02 ` Dave Hansen
2011-02-01 15:02 ` Dave Hansen
2011-02-01 16:09 ` Andrea Arcangeli
2011-02-01 16:09 ` Andrea Arcangeli
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:34 ` Dave Hansen
2011-02-03 21:34 ` Dave Hansen
2011-02-01 0:34 ` [RFC][PATCH 6/6] have smaps show transparent huge pages Dave Hansen
2011-02-01 0:34 ` Dave Hansen
2011-02-01 10:12 ` Johannes Weiner
2011-02-01 10:12 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:22 ` David Rientjes
2011-02-01 15:38 ` [RFC][PATCH 0/6] more detailed per-process transparent hugepage statistics Andrea Arcangeli
2011-02-01 15:38 ` Andrea Arcangeli
2011-02-01 17:15 ` Dave Hansen
2011-02-01 17:15 ` Dave Hansen
2011-02-01 20:39 ` Andrea Arcangeli
2011-02-01 20:39 ` Andrea Arcangeli
2011-02-01 20:56 ` Dave Hansen
2011-02-01 20:56 ` Dave Hansen
2011-02-02 0:07 ` Andrea Arcangeli
2011-02-02 0:07 ` Andrea Arcangeli
2011-02-08 17:54 ` Dave Hansen [this message]
2011-02-08 17:54 ` Dave Hansen
2011-02-08 18:17 ` Andrea Arcangeli
2011-02-08 18:17 ` Andrea Arcangeli
2011-02-03 21:54 ` David Rientjes
2011-02-03 21:54 ` David Rientjes
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