linux-kernel - Re: [PATCH] mm/vmstat: Reduce zone lock hold time when reading /proc/pagetypeinfo

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Date:   Fri, 25 Oct 2019 09:38:01 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Qian Cai <cai@....pw>
Cc:     Waiman Long <longman@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jann Horn <jannh@...gle.com>, Song Liu <songliubraving@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rafael Aquini <aquini@...hat.com>
Subject: Re: [PATCH] mm/vmstat: Reduce zone lock hold time when reading
 /proc/pagetypeinfo

On Thu, Oct 24, 2019 at 06:51:54PM +0800, Qian Cai wrote:
> 
> 
> > On Oct 24, 2019, at 1:34 AM, Feng Tang <feng.tang@...el.com> wrote:
> > 
> > One example is, there was a platform with limited DRAM, so it preset
> > some CMA memory for camera's big buffer allocation use, while it let 
> > these memory to be shared by others when camera was not used. And
> > after long time running, the cma region got fragmented and camera
> > app started to fail due to the buffer allocation failure. And during
> > debugging, we kept monitoring the buddy info for different migrate
> > types.
> 
> For CMA-specific debugging, why CMA debugfs is not enough?

We care about change flow of the numbers of different orders for cma
and other migrate types, sometimes I just use one simple cmd
	watch -d 'cat /proc/pagetypeinfo'
which shows direct and dynamic flows.

Thanks,
Feng