From: Suleiman Souhlal <suleiman@google.com>
To: Roman Gushchin <guro@fb.com>
Cc: "Michal Koutný" <mkoutny@suse.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"Michal Hocko" <mhocko@kernel.org>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Kernel Team" <Kernel-team@fb.com>,
"Shakeel Butt" <shakeelb@google.com>,
"Vladimir Davydov" <vdavydov.dev@gmail.com>,
"Waiman Long" <longman@redhat.com>
Subject: Re: [PATCH RFC 00/14] The new slab memory controller
Date: Wed, 2 Oct 2019 22:00:07 +0900 [thread overview]
Message-ID: <CABCjUKBZxJJrUzpgXafqtXOYXZbYXEh0ku8fZLpPHXWnrTw1hg@mail.gmail.com> (raw)
In-Reply-To: <20191002020906.GB6436@castle.dhcp.thefacebook.com>
On Wed, Oct 2, 2019 at 11:09 AM Roman Gushchin <guro@fb.com> wrote:
>
> On Tue, Oct 01, 2019 at 05:12:02PM +0200, Michal Koutný wrote:
> > On Thu, Sep 05, 2019 at 02:45:44PM -0700, Roman Gushchin <guro@fb.com> wrote:
> > > Roman Gushchin (14):
> > > [...]
> > > mm: memcg/slab: use one set of kmem_caches for all memory cgroups
> > From that commit's message:
> >
> > > 6) obsoletes kmem.slabinfo cgroup v1 interface file, as there are
> > > no per-memcg kmem_caches anymore (empty output is printed)
> >
> > The empty file means no allocations took place in the particular cgroup.
> > I find this quite a surprising change for consumers of these stats.
> >
> > I understand obtaining the same data efficiently from the proposed
> > structures is difficult, however, such a change should be avoided. (In
> > my understanding, obsoleted file ~ not available in v2, however, it
> > should not disappear from v1.)
>
> Well, my assumption is that nobody is using this file for anything except
> debugging purposes (I might be wrong, if somebody has an automation based
> on it, please, let me know). A number of allocations of each type per memory
> cgroup is definitely a useful debug information, but currently it barely works
> (displayed numbers show mostly the number of allocated pages, not the number
> of active objects). We can support it, but it comes with the price, and
> most users don't really need it. So I don't think it worth it to make all
> allocations slower just to keep some debug interface working for some
> cgroup v1 users. Do you have examples when it's really useful and worth
> extra cpu cost?
>
> Unfortunately, we can't enable it conditionally, as a user can switch
> between cgroup v1 and cgroup v2 memory controllers dynamically.
kmem.slabinfo has been absolutely invaluable for debugging, in my experience.
I am however not aware of any automation based on it.
Maybe it might be worth adding it to cgroup v2 and have a CONFIG
option to enable it?
-- Suleiman
next prev parent reply other threads:[~2019-10-02 13:00 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 21:45 [PATCH RFC 00/14] The new slab memory controller Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 01/14] mm: memcg: subpage charging API Roman Gushchin
2019-09-16 12:56 ` Johannes Weiner
2019-09-17 2:27 ` Roman Gushchin
2019-09-17 8:50 ` Johannes Weiner
2019-09-17 18:33 ` Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 02/14] mm: memcg: introduce mem_cgroup_ptr Roman Gushchin
2019-09-05 22:34 ` Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 03/14] mm: vmstat: use s32 for vm_node_stat_diff in struct per_cpu_nodestat Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 04/14] mm: vmstat: convert slab vmstat counter to bytes Roman Gushchin
2019-09-16 12:38 ` Johannes Weiner
2019-09-17 2:08 ` Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 05/14] mm: memcg/slab: allocate space for memcg ownership data for non-root slabs Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 06/14] mm: slub: implement SLUB version of obj_to_index() Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 07/14] mm: memcg/slab: save memcg ownership data for non-root slab objects Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 08/14] mm: memcg: move memcg_kmem_bypass() to memcontrol.h Roman Gushchin
2019-09-05 21:45 ` [PATCH RFC 09/14] mm: memcg: introduce __mod_lruvec_memcg_state() Roman Gushchin
2019-09-05 22:37 ` [PATCH RFC 02/14] mm: memcg: introduce mem_cgroup_ptr Roman Gushchin
2019-09-17 19:48 ` [PATCH RFC 00/14] The new slab memory controller Waiman Long
2019-09-17 21:24 ` Roman Gushchin
2019-09-19 13:39 ` Suleiman Souhlal
2019-09-19 16:22 ` Roman Gushchin
2019-09-19 21:10 ` Suleiman Souhlal
2019-09-19 21:40 ` Roman Gushchin
2019-10-01 15:12 ` Michal Koutný
2019-10-02 2:09 ` Roman Gushchin
2019-10-02 13:00 ` Suleiman Souhlal [this message]
2019-10-03 10:47 ` Michal Koutný
2019-10-03 15:52 ` Roman Gushchin
2019-12-09 9:17 ` [PATCH 00/16] " Bharata B Rao
2019-12-09 11:56 ` Bharata B Rao
2019-12-09 18:04 ` Roman Gushchin
2019-12-10 6:23 ` Bharata B Rao
2019-12-10 18:05 ` Roman Gushchin
2020-01-13 8:47 ` Bharata B Rao
2020-01-13 15:31 ` Roman Gushchin
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