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From:   Guilherme Piccoli <gpiccoli@canonical.com>
Date:   Mon, 11 May 2020 08:26:28 -0300
Message-ID: <CAHD1Q_zrQmUTRpdW3bZ0CRKuu2dKgueXUjqCNtC5oyZ67CGp2A@mail.gmail.com>
Subject: Re: [PATCH] mm, compaction: Indicate when compaction is manually
 triggered by sysctl
To:     David Rientjes <rientjes@google.com>
Cc:     "Guilherme G. Piccoli" <kernel@gpiccoli.net>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Gavin Guo <gavin.guo@canonical.com>,
        Mel Gorman <mgorman@techsingularity.net>
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On Sun, May 10, 2020 at 10:25 PM David Rientjes <rientjes@google.com> wrote:
> [...]
> The kernel log is not preferred for this (or drop_caches, really) because
> the amount of info can causing important information to be lost.  We don't
> really gain anything by printing that someone manually triggered
> compaction; they could just write to the kernel log themselves if they
> really wanted to.  The reverse is not true: we can't suppress your kernel
> message with this patch.
>
> Instead, a statsfs-like approach could be used to indicate when this has
> happened and there is no chance of losing events because it got scrolled
> off the kernel log.  It has the added benefit of not requiring the entire
> log to be parsed for such events.

OK, agreed! Let's forget the kernel log. So, do you think the way to
go is the statsfs, not a zoneinfo stat, a per-node thing? I'm saying
that because kernel mm subsystem statistics seem pretty.."comfortable"
the way they are, in files like vmstat, zoneinfo, etc. Let me know
your thoughts on this, if I could work on that or should wait statsfs.
Thanks,


Guilherme