From: Daniel Walker <danielwa@cisco.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, "Khalid Mughal (khalidm)" <khalidm@cisco.com>,
"xe-kernel@external.cisco.com" <xe-kernel@external.cisco.com>,
Rik van Riel <riel@redhat.com>
Subject: Re: computing drop-able caches
Date: Fri, 29 Jan 2016 13:21:47 -0800 [thread overview]
Message-ID: <56ABD7EB.7000404@cisco.com> (raw)
In-Reply-To: <20160129015534.GA6401@cmpxchg.org>
On 01/28/2016 05:55 PM, Johannes Weiner wrote:
> On Thu, Jan 28, 2016 at 05:29:41PM -0800, Daniel Walker wrote:
>> On 01/28/2016 05:03 PM, Daniel Walker wrote:
>> [regarding MemAvaiable]
>>
>> This new metric purportedly helps usrespace assess available memory. But,
>> its again based on heuristic, it takes 1/2 of page cache as reclaimable..
> No, it takes the smaller value of cache/2 and the low watermark, which
> is a fraction of memory. Actually, that does look a little weird. Rik?
>
> We don't age cache without memory pressure, you don't know how much is
> used until you start taking some away. Heuristics is all we can offer.
With a simple busybox root system I get this,
MemTotal: 16273996 kB
MemFree: 16137920 kB
MemAvailable: 16046132 kB
shouldn't MemAvailable be at least the same as MemFree ? I changed the
code somewhat so it subtracted the wmark_low only, or the pagecache/2
only, both are still under MemFree. This system has very little
drop-able caches.
Daniel
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next prev parent reply other threads:[~2016-01-29 21:21 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 23:42 computing drop-able caches Daniel Walker
2016-01-28 23:58 ` Johannes Weiner
2016-01-29 1:03 ` Daniel Walker
2016-01-29 1:29 ` Daniel Walker
2016-01-29 1:55 ` Johannes Weiner
2016-01-29 21:21 ` Daniel Walker [this message]
2016-01-29 22:33 ` Johannes Weiner
2016-01-29 22:41 ` Rik van Riel
2016-02-08 20:57 ` Khalid Mughal (khalidm)
2016-02-10 18:04 ` Daniel Walker
2016-02-10 18:13 ` Dave Hansen
2016-02-10 19:11 ` Daniel Walker
2016-02-11 22:11 ` Rik van Riel
2016-02-12 18:01 ` Khalid Mughal (khalidm)
2016-02-12 21:46 ` Dave Hansen
2016-02-12 22:15 ` Johannes Weiner
2016-02-12 18:06 ` Dave Hansen
2016-02-12 18:15 ` Daniel Walker
2016-02-12 18:18 ` Dave Hansen
2016-02-12 18:25 ` Daniel Walker
2016-02-12 20:15 ` Daniel Walker
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