linux-kernel - Re: [[repost]RFC PATCH] mm/workingset : judge file page activity via timestamp

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Date:   Mon, 6 May 2019 10:57:27 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Zhaoyang Huang <huangzhaoyang@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        Roman Gushchin <guro@...com>, Jeff Layton <jlayton@...hat.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [[repost]RFC PATCH] mm/workingset : judge file page activity via
 timestamp

On Sun, Apr 28, 2019 at 03:44:34PM +0800, Zhaoyang Huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> this patch introduce timestamp into workingset's entry and judge if the page is
> active or inactive via active_file/refault_ratio instead of refault distance.
> 
> The original thought is coming from the logs we got from trace_printk in this
> patch, we can find about 1/5 of the file pages' refault are under the
> scenario[1],which will be counted as inactive as they have a long refault distance
> in between access. However, we can also know from the time information that the
> page refault quickly as comparing to the average refault time which is calculated
> by the number of active file and refault ratio. We want to save these kinds of
> pages from evicted earlier as it used to be via setting it to ACTIVE instead.
> The refault ratio is the value which can reflect lru's average file access
> frequency in the past and provide the judge criteria for page's activation.
> 
> The patch is tested on an android system and reduce 30% of page faults, while
> 60% of the pages remain the original status as (refault_distance < active_file)
> indicates. Pages status got from ftrace during the test can refer to [2].
> 
> [1]
> system_server workingset_refault: WKST_ACT[0]:rft_dis 265976, act_file 34268 rft_ratio 3047 rft_time 0 avg_rft_time 11 refault 295592 eviction 29616 secs 97 pre_secs 97
> HwBinder:922  workingset_refault: WKST_ACT[0]:rft_dis 264478, act_file 35037 rft_ratio 3070 rft_time 2 avg_rft_time 11 refault 310078 eviction 45600 secs 101 pre_secs 99
> 
> [2]
> WKST_ACT[0]:   original--INACTIVE  commit--ACTIVE
> WKST_ACT[1]:   original--ACTIVE    commit--ACTIVE
> WKST_INACT[0]: original--INACTIVE  commit--INACTIVE
> WKST_INACT[1]: original--ACTIVE    commit--INACTIVE
> 
> Signed-off-by: Zhaoyang Huang <huangzhaoyang@...il.com>

Nacked-by: Johannes Weiner <hannes@...xchg.org>

You haven't addressed any of the questions raised during previous
submissions.