linux-kernel - Re: High kmalloc-32 slab cache consumption with 10k containers

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Message-ID: <YG2diKMPNSK2cMyG@dhcp22.suse.cz>
Date:   Wed, 7 Apr 2021 13:54:48 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Bharata B Rao <bharata@...ux.ibm.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        aneesh.kumar@...ux.ibm.com
Subject: Re: High kmalloc-32 slab cache consumption with 10k containers

On Mon 05-04-21 11:18:48, Bharata B Rao wrote:
> Hi,
> 
> When running 10000 (more-or-less-empty-)containers on a bare-metal Power9
> server(160 CPUs, 2 NUMA nodes, 256G memory), it is seen that memory
> consumption increases quite a lot (around 172G) when the containers are
> running. Most of it comes from slab (149G) and within slab, the majority of
> it comes from kmalloc-32 cache (102G)

Is this 10k cgroups a testing enviroment or does anybody really use that
in production? I would be really curious to hear how that behaves when
those containers are not idle. E.g. global memory reclaim iterating over
10k memcgs will likely be very visible. I do remember playing with
similar setups few years back and the overhead was very high.
-- 
Michal Hocko
SUSE Labs