linux-kernel - Re: SLUB: percpu partial object count is highly inaccurate, causing some memory wastage and maybe also worse tail latencies?

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Message-ID: <20210112002720.GA35320@carbon.dhcp.thefacebook.com>
Date:   Mon, 11 Jan 2021 16:27:20 -0800
From:   Roman Gushchin <guro@...com>
To:     Jann Horn <jannh@...gle.com>
CC:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Minchan Kim <minchan@...nel.org>
Subject: Re: SLUB: percpu partial object count is highly inaccurate, causing
 some memory wastage and maybe also worse tail latencies?

On Tue, Jan 12, 2021 at 12:12:47AM +0100, Jann Horn wrote:
> [This is not something I intend to work on myself. But since I
> stumbled over this issue, I figured I should at least document/report
> it, in case anyone is willing to pick it up.]

Hi, Jann!

Thank you very much for this report!

It should be less of a problem since 5.9, but still on a machine with
many CPUs a non-trivial amount of memory is wasted.

I'll definitely take a look.

Thanks!