linux-kernel - Re: [PATCH] mm,page_alloc,cma: configurable CMA utilization

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Date:   Thu, 2 Feb 2023 12:13:02 -0800
From:   Sukadev Bhattiprolu <quic_sukadev@...cinc.com>
To:     Roman Gushchin <roman.gushchin@...ux.dev>
CC:     Chris Goldsworthy <quic_cgoldswo@...cinc.com>,
        Rik van Riel <riel@...riel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Vlastimil Babka <vbabka@...e.cz>,
        Joonsoo Kim <js1304@...il.com>,
        Minchan Kim <minchan@...nel.org>,
        Georgi Djakov <quic_c_gdjako@...cinc.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm,page_alloc,cma: configurable CMA utilization


Hi Roman,

On Wed, Feb 01, 2023 at 11:00:25AM -0800, Roman Gushchin wrote:
> Then _maybe_ a new knob is justified, at least I don't have better ideas.
> Rik, do you have any input here?
> 
> Let's then define it in a more generic way and _maybe_ move to the cma
> sysfs/debugfs (not 100% sure about this part, but probably worth exploring).

We should be able to use a sysfs parameter too. Will try that out. But could
you elaborate on what is more generic way?

Also regarding following in the earlier message:

> Also, if decide to go with a new sysctl, we probably want to define it differently,
> e.g. as a [0-1000)/1000 of the zone size. But, honestly, I'm not sold yet.

Are you saying that the ratio should be limited to 1000th of the zone size?
Or of the free pages in the zone? If the zone is large, 1000th of it would
still be quite big?

Sukadev