From: Rik van Riel <riel@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ying Han <yinghan@google.com>, Michal Hocko <mhocko@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>, Mel Gorman <mel@csn.ul.ie>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Hillf Danton <dhillf@gmail.com>, Hugh Dickins <hughd@google.com>,
Dan Magenheimer <dan.magenheimer@oracle.com>,
linux-mm@kvack.org, kvm@vger.kernel.org,
Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH] kvm: don't call mmu_shrinker w/o used_mmu_pages
Date: Fri, 20 Apr 2012 18:53:00 -0400 [thread overview]
Message-ID: <4F91E8CC.5080409@redhat.com> (raw)
In-Reply-To: <20120420151143.433c514e.akpm@linux-foundation.org>
On 04/20/2012 06:11 PM, Andrew Morton wrote:
> On Fri, 13 Apr 2012 15:38:41 -0700
> Ying Han<yinghan@google.com> wrote:
>
>> The mmu_shrink() is heavy by itself by iterating all kvms and holding
>> the kvm_lock. spotted the code w/ Rik during LSF, and it turns out we
>> don't need to call the shrinker if nothing to shrink.
>> @@ -3900,6 +3905,9 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
>> if (nr_to_scan == 0)
>> goto out;
>>
>> + if (!get_kvm_total_used_mmu_pages())
>> + return 0;
>> +
> Do we actually know that this patch helps anything? Any measurements? Is
> kvm_total_used_mmu_pages==0 at all common?
>
On re-reading mmu.c, it looks like even with EPT or NPT,
we end up creating mmu pages for the nested page tables.
I have not had the time to look into it more, but it would
be nice to know if the patch has any effect at all.
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next prev parent reply other threads:[~2012-04-20 22:53 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-13 22:38 [PATCH] kvm: don't call mmu_shrinker w/o used_mmu_pages Ying Han
2012-04-14 11:44 ` Hillf Danton
2012-04-16 16:43 ` Ying Han
2012-04-20 22:11 ` Andrew Morton
2012-04-20 22:11 ` Andrew Morton
2012-04-20 22:53 ` Rik van Riel [this message]
2012-04-20 23:07 ` Ying Han
2012-04-21 1:56 ` Takuya Yoshikawa
2012-04-21 2:15 ` Mike Waychison
2012-04-21 2:29 ` Takuya Yoshikawa
2012-04-21 2:29 ` Takuya Yoshikawa
2012-04-21 2:48 ` Mike Waychison
2012-04-21 2:48 ` Mike Waychison
2012-04-22 9:16 ` Avi Kivity
2012-04-22 19:05 ` Eric Northup
2012-04-23 8:37 ` Avi Kivity
2012-04-22 9:04 ` Avi Kivity
2012-04-22 9:35 ` Avi Kivity
2012-04-23 16:40 ` Ying Han
2012-04-23 16:48 ` Rik van Riel
2012-04-23 16:57 ` Avi Kivity
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