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Date:   Thu, 14 Jan 2021 10:27:40 +0100
From:   Vlastimil Babka <>
To:     Christoph Lameter <>, Jann Horn <>
Cc:     Pekka Enberg <>,
        David Rientjes <>,
        Joonsoo Kim <>,
        Andrew Morton <>,
        Linux-MM <>,
        kernel list <>,
        Thomas Gleixner <>,
        Sebastian Andrzej Siewior <>,
        Roman Gushchin <>,
        Johannes Weiner <>,
        Shakeel Butt <>,
        Suren Baghdasaryan <>,
        Minchan Kim <>,
        Michal Hocko <>
Subject: SLUB: percpu partial object count is highly inaccurate, causing some
 memory wastage and maybe also worse tail latencies?

On 1/12/21 5:35 PM, Christoph Lameter wrote:
> On Tue, 12 Jan 2021, 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.]
> Well yeah all true. There is however a slabinfo tool that has an -s option
> to shrink all slabs.
> 	slabinfo -s
> So you could put that somewhere that executes if the system is
> idle or put it into cron or so.

Hm this would be similar to recommending a periodical echo > drop_caches
operation. We actually discourage from that (and yeah, some tools do that, and
we now report those in dmesg). I believe the kernel should respond to memory
pressure and not OOM prematurely by itself, including SLUB.

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