From: Rik van Riel <riel@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>, Daniel Walker <danielwa@cisco.com>
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>
Subject: Re: computing drop-able caches
Date: Fri, 29 Jan 2016 17:41:43 -0500 [thread overview]
Message-ID: <56ABEAA7.1020706@redhat.com> (raw)
In-Reply-To: <20160129015534.GA6401@cmpxchg.org>
On 01/28/2016 08:55 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?
No, not quite. The page cache calculation spans two lines:
pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
pagecache -= min(pagecache / 2, wmark_low);
The assumption is that ALL of active & inactive file LRUs are
freeable, except for the minimum of the low watermark, or
half the page cache.
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>, Daniel Walker <danielwa@cisco.com>
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>
Subject: Re: computing drop-able caches
Date: Fri, 29 Jan 2016 17:41:43 -0500 [thread overview]
Message-ID: <56ABEAA7.1020706@redhat.com> (raw)
In-Reply-To: <20160129015534.GA6401@cmpxchg.org>
On 01/28/2016 08:55 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?
No, not quite. The page cache calculation spans two lines:
pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
pagecache -= min(pagecache / 2, wmark_low);
The assumption is that ALL of active & inactive file LRUs are
freeable, except for the minimum of the low watermark, or
half the page cache.
--
All rights reversed
next prev parent reply other threads:[~2016-01-29 22:41 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 23:42 computing drop-able caches Daniel Walker
2016-01-28 23:42 ` Daniel Walker
2016-01-28 23:58 ` Johannes Weiner
2016-01-28 23:58 ` Johannes Weiner
2016-01-29 1:03 ` Daniel Walker
2016-01-29 1:03 ` Daniel Walker
2016-01-29 1:29 ` Daniel Walker
2016-01-29 1:55 ` Johannes Weiner
2016-01-29 1:55 ` Johannes Weiner
2016-01-29 21:21 ` Daniel Walker
2016-01-29 21:21 ` Daniel Walker
2016-01-29 22:33 ` Johannes Weiner
2016-01-29 22:33 ` Johannes Weiner
2016-01-29 22:41 ` Rik van Riel [this message]
2016-01-29 22:41 ` Rik van Riel
2016-02-08 20:57 ` Khalid Mughal (khalidm)
2016-02-08 20:57 ` Khalid Mughal (khalidm)
2016-02-10 18:04 ` Daniel Walker
2016-02-10 18:04 ` Daniel Walker
2016-02-10 18:13 ` Dave Hansen
2016-02-10 18:13 ` Dave Hansen
2016-02-10 19:11 ` Daniel Walker
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 21:46 ` Dave Hansen
2016-02-12 21:46 ` Dave Hansen
2016-02-12 22:15 ` Johannes Weiner
2016-02-12 22:15 ` Johannes Weiner
2016-02-12 22:15 ` Johannes Weiner
2016-02-12 18:06 ` Dave Hansen
2016-02-12 18:06 ` Dave Hansen
2016-02-12 18:15 ` Daniel Walker
2016-02-12 18:15 ` Daniel Walker
2016-02-12 18:18 ` Dave Hansen
2016-02-12 18:18 ` Dave Hansen
2016-02-12 18:25 ` Daniel Walker
2016-02-12 18:25 ` Daniel Walker
2016-02-12 20:15 ` Daniel Walker
2016-02-12 20:15 ` Daniel Walker
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