Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 28 Feb 2020 18:21:45 +0800
From:   Aaron Lu <aaron.lwe@gmail.com>
To:     Joonsoo Kim <js1304@gmail.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Michal Hocko <mhocko@kernel.org>,
        Hugh Dickins <hughd@google.com>,
        Minchan Kim <minchan@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>, kernel-team@lge.com,
        Huang Ying <ying.huang@intel.com>
Subject: Re: [PATCH v2 0/9] workingset protection/detection on the anonymous
 LRU list
Message-ID: <20200228102145.GA675897@ziqianlu-desktop.localdomain>
References: <1582175513-22601-1-git-send-email-iamjoonsoo.kim@lge.com>
 <20200226193942.30049da9c090b466bdc5ec23@linux-foundation.org>
 <20200227134806.GC39625@cmpxchg.org>
 <20200228032358.GB634650@ziqianlu-desktop.localdomain>
 <20200228040214.GA21040@js1304-desktop>
 <20200228055726.GA674737@ziqianlu-desktop.localdomain>
 <20200228065214.GA17349@js1304-desktop>
 <20200228091700.GA675567@ziqianlu-desktop.localdomain>
 <20200228095534.GA30796@js1304-desktop>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20200228095534.GA30796@js1304-desktop>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Feb 28, 2020 at 06:56:11PM +0900, Joonsoo Kim wrote:
> On Fri, Feb 28, 2020 at 05:17:00PM +0800, Aaron Lu wrote:
> > I think LKP robot has captured these two metrics but the report didn't
> > show them, which means the number is about the same with or without
> > patch #1.
> 
> robot showed these two metrics. See below.
> 
>   50190319 ? 31%     -35.7%   32291856 ? 14%  proc-vmstat.pswpin
>   56429784 ? 21%     -42.6%   32386842 ? 14%  proc-vmstat.pswpout
> 
> pswpin/out are improved.

Oh yes, I checked the vmstat part, while I should check proc-vmstat
part...Sorry for missing this.

> 
> > > with patch #1. With large inactive list, we can easily find the
> > > frequently referenced page and it would result in less swap in/out.
> > 
> > But with small inactive list, the pages that would be on inactive list
> > will stay on active list? I think the larger inactive list is mainly
> > used to give the anon page a chance to be promoted to active list now
> > that anon pages land on inactive list first, but on reclaim, I don't see
> > how a larger inactive list can cause fewer swap outs.
> 
> Point is that larger inactive LRU helps to find hot pages and these
> hot pages leads to more cache hits.
> 
> When a cache hit happens, no swap outs happens. But, if a cache miss
> happens, a new page is added to the LRU and then it causes the reclaim
> and swap out.

OK, I think I start to get your point. Your explanation makes sense.

> > Forgive me for my curiosity and feel free to ignore my question as I
> > don't want to waste your time on this. Your patchset looks a worthwhile
> > thing to do, it's just the robot's report on patch1 seems er...
> 
> I appreciate your attention. Feel free to ask. :)

Thanks a lot for your patience and nice explanation :-)