linux-kernel - Re: SLUB: purpose of sysfs events on cache creation/removal

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Message-ID: <20191126165420.GL20912@dhcp22.suse.cz>
Date:   Tue, 26 Nov 2019 17:54:20 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Christopher Lameter <cl@...ux.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: SLUB: purpose of sysfs events on cache creation/removal

On Tue 26-11-19 16:32:56, Cristopher Lameter wrote:
> On Tue, 26 Nov 2019, Michal Hocko wrote:
> 
> > Hi,
> > I have just learnt about KOBJ_{ADD,REMOVE} sysfs events triggered on
> > kmem cache creation/removal when SLUB is configured. This functionality
> > goes all the way down to initial SLUB merge. I do not see any references
> > in the Documentation explaining what those events are used for and
> > whether there are any real users.
> >
> > Could you shed some more light into this?
> 
> I have no idea about what this is.

It seems to be there since the initial merge. I suspect this is just
following a generic sysfs rule that each file has to provide those
events?

> There have been many people who
> reworked the sysfs support and this has been the cause for a lot of
> breakage over the years.

Remember any specifics?

I am mostly interested in potential users. In other words I am thinking
to suppress those events. There is already ke knob to control existence
of memcg caches but I do not see anything like this for root caches.
-- 
Michal Hocko
SUSE Labs