linux-kernel - Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint

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Message-ID: <20161230173023.GA4962@dhcp22.suse.cz>
Date:   Fri, 30 Dec 2016 18:30:24 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Hillf Danton <hillf.zj@...baba-inc.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint

On Fri 30-12-16 17:37:42, Michal Hocko wrote:
> On Sat 31-12-16 01:04:56, Minchan Kim wrote:
[...]
> > > 	- nr_rotated pages which tells us that we are hitting referenced
> > > 	  pages which are deactivated. If this is a large part of the
> > > 	  reported nr_deactivated pages then the active list is too small
> > 
> > It might be but not exactly. If your goal is to know LRU size, it can be
> > done in get_scan_count. I tend to agree LRU size is helpful for
> > performance analysis because decreased LRU size signals memory shortage
> > then performance drop.
> 
> No, I am not really interested in the exact size but rather to allow to
> find whether we are aging the active list too early...

But thinking about that some more, maybe sticking with the nr_rotated
terminology is rather confusing and displaying the value as nr_referenced
would be more clear.
-- 
Michal Hocko
SUSE Labs