From: ebiederm@xmission.com (Eric W. Biederman)
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
lnxninja@linux.vnet.ibm.com
Subject: Re: [RFC][PATCH] update /proc/sys/vm/drop_caches documentation
Date: Wed, 15 Sep 2010 14:34:12 -0700 [thread overview]
Message-ID: <m17him4ror.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <1284578821.27089.17409.camel@nimitz> (Dave Hansen's message of "Wed, 15 Sep 2010 12:27:01 -0700")
Dave Hansen <dave@linux.vnet.ibm.com> writes:
> On Wed, 2010-09-15 at 11:37 -0700, Eric W. Biederman wrote:
>> > I'm worried that there are users out there experiencing real problems
>> > that aren't reporting it because "workarounds" like this just paper over
>> > the issue.
>>
>> For what it is worth. I had a friend ask me about a system that had 50%
>> of it's memory consumed by slab caches. 20GB out of 40GB. The kernel
>> was suse? 2.6.27 so it's old, but if you are curious.
>> /proc/sys/vm/drop_caches does nothing in that case.
>
> Was it the reclaimable caches doing it, though? The other really common
> cause is kmalloc() leaks.
It was reclaimable caches. He kept seeing the cache sizes of the
problem caches shrink. On an idle system he said he was seeing
about 16MB/min getting free or something like that. Something
that would take hours and hours before things freed up.
I asked and my friend told me that according to slabtop the slab
with the most memory used kept changing dramatically and he could
not see a pattern.
So at least on one old kernel on one strange workload there was a problem.
Eric
WARNING: multiple messages have this Message-ID (diff)
From: ebiederm@xmission.com (Eric W. Biederman)
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
lnxninja@linux.vnet.ibm.com
Subject: Re: [RFC][PATCH] update /proc/sys/vm/drop_caches documentation
Date: Wed, 15 Sep 2010 14:34:12 -0700 [thread overview]
Message-ID: <m17him4ror.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <1284578821.27089.17409.camel@nimitz> (Dave Hansen's message of "Wed, 15 Sep 2010 12:27:01 -0700")
Dave Hansen <dave@linux.vnet.ibm.com> writes:
> On Wed, 2010-09-15 at 11:37 -0700, Eric W. Biederman wrote:
>> > I'm worried that there are users out there experiencing real problems
>> > that aren't reporting it because "workarounds" like this just paper over
>> > the issue.
>>
>> For what it is worth. I had a friend ask me about a system that had 50%
>> of it's memory consumed by slab caches. 20GB out of 40GB. The kernel
>> was suse? 2.6.27 so it's old, but if you are curious.
>> /proc/sys/vm/drop_caches does nothing in that case.
>
> Was it the reclaimable caches doing it, though? The other really common
> cause is kmalloc() leaks.
It was reclaimable caches. He kept seeing the cache sizes of the
problem caches shrink. On an idle system he said he was seeing
about 16MB/min getting free or something like that. Something
that would take hours and hours before things freed up.
I asked and my friend told me that according to slabtop the slab
with the most memory used kept changing dramatically and he could
not see a pattern.
So at least on one old kernel on one strange workload there was a problem.
Eric
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next prev parent reply other threads:[~2010-09-15 21:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 23:47 [RFC][PATCH] update /proc/sys/vm/drop_caches documentation Dave Hansen
2010-09-14 23:47 ` Dave Hansen
2010-09-15 4:33 ` KAMEZAWA Hiroyuki
2010-09-15 4:33 ` KAMEZAWA Hiroyuki
2010-09-15 4:53 ` KOSAKI Motohiro
2010-09-15 4:53 ` KOSAKI Motohiro
2010-09-15 6:14 ` Dave Hansen
2010-09-15 6:14 ` Dave Hansen
2010-09-15 18:37 ` Eric W. Biederman
2010-09-15 18:37 ` Eric W. Biederman
2010-09-15 19:27 ` Dave Hansen
2010-09-15 19:27 ` Dave Hansen
2010-09-15 21:34 ` Eric W. Biederman [this message]
2010-09-15 21:34 ` Eric W. Biederman
2010-09-15 19:24 ` Tim Pepper
2010-09-15 19:24 ` Tim Pepper
2010-09-16 0:12 ` KAMEZAWA Hiroyuki
2010-09-16 0:12 ` KAMEZAWA Hiroyuki
2010-09-16 1:21 ` Dave Hansen
2010-09-16 1:21 ` Dave Hansen
2010-09-16 1:33 ` KAMEZAWA Hiroyuki
2010-09-16 1:33 ` KAMEZAWA Hiroyuki
2010-09-24 13:02 ` Pavel Machek
2010-09-24 13:02 ` Pavel Machek
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