linux-kernel - Re: [PATCH -next] mm: introduce per-node proactive reclaim interface

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Message-Id: <20240904181543.02de2242490cf233c7879697@linux-foundation.org>
Date: Wed, 4 Sep 2024 18:15:43 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Davidlohr Bueso <dave@...olabs.net>
Cc: linux-mm@...ck.org, mhocko@...nel.org, rientjes@...gle.com,
 yosryahmed@...gle.com, hannes@...xchg.org, almasrymina@...gle.com,
 roman.gushchin@...ux.dev, gthelen@...gle.com, dseo3@....edu,
 a.manzanares@...sung.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] mm: introduce per-node proactive reclaim
 interface

On Wed, 4 Sep 2024 18:08:05 -0700 Davidlohr Bueso <dave@...olabs.net> wrote:

> On Wed, 04 Sep 2024, Andrew Morton wrote:\n
> >On Wed,  4 Sep 2024 09:27:40 -0700 Davidlohr Bueso <dave@...olabs.net> wrote:
> >
> >> This adds support for allowing proactive reclaim in general on a
> >> NUMA system. A per-node interface extends support for beyond a
> >> memcg-specific interface, respecting the current semantics of
> >> memory.reclaim: respecting aging LRU and not supporting
> >> artificially triggering eviction on nodes belonging to non-bottom
> >> tiers.
> >>
> >> This patch allows userspace to do:
> >>
> >>      echo 512M swappiness=10 > /sys/devices/system/node/nodeX/reclaim
> >
> >One value per sysfs file is a rule.
> 
> I wasn't aware of it as a rule - is this documented somewhere?

Documentation/filesystems/sysfs.rst, line 62.  Also lots of gregkh
grumpygrams :)

> I ask because I see some others are using space-separated parameters, ie:
> 
> /sys/bus/usb/drivers/foo/new_id
> 
> ... or colons. What would be acceptable? echo "512M:10" > ... ?

Kinda cheating.  But the rule gets violated a lot.