linux-kernel - Re: [PATCH] mm/slub: Detach node lock from counting free objects

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Date:   Wed, 12 Feb 2020 14:56:15 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Wen Yang <wenyang@...ux.alibaba.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Xunlei Pang <xlpang@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: Detach node lock from counting free objects

On Sat, 8 Feb 2020 21:41:49 +0000 (UTC) Christopher Lameter <cl@...ux.com> wrote:

> On Sat, 8 Feb 2020, Wen Yang wrote:
> 
> > I would greatly appreciate it if you kindly give me some feedback on this
> > patch.
> 
> I think the measure is too severe given its use and the general impact on code.

Severe in what way?  It's really a quite simple change, although quite
a few edits were needed.

> Maybe avoid taking the lock or reducing the time a lock is taken when reading /proc/slabinfo is
> the best approach?
> 
> Also you could cache the value in the userspace application? Why is this
> value read continually?

: reading "/proc/slabinfo" can possibly block the slab allocation on
: another CPU for a while, 200ms in extreme cases

That was bad of us.  It would be good to stop doing this.