From: Christoph Lameter <cl@linux.com>
To: Jann Horn <jannh@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
kernel list <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeelb@google.com>,
Suren Baghdasaryan <surenb@google.com>,
Minchan Kim <minchan@kernel.org>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: SLUB: percpu partial object count is highly inaccurate, causing some memory wastage and maybe also worse tail latencies?
Date: Thu, 14 Jan 2021 09:04:26 +0000 (UTC) [thread overview]
Message-ID: <alpine.DEB.2.22.394.2101140902210.38517@www.lameter.com> (raw)
In-Reply-To: <CAG48ez2-DzC4qf_vzqj+VoGu4nM7275WmyxiPMT7dAp+MHDtOg@mail.gmail.com>
On Wed, 13 Jan 2021, Jann Horn wrote:
> Some brainstorming:
>
> Maybe you could have an atomic counter in kmem_cache_cpu that tracks
> the number of empty frozen pages that are associated with a specific
> CPU? So the freeing slowpath would do its cmpxchg_double, and if the
The latencies of these functions are so low that any additional counter
will have significant performance impacts. An atomic counter would be waay
out there.
> You could additionally have a plain percpu counter, not tied to the
The performance critical counters are already all per cpu. I enhanced the
percpu subsystem specifically to support latency critical operations in
the fast path of the slab allocators.
next prev parent reply other threads:[~2021-01-14 9:04 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 23:12 SLUB: percpu partial object count is highly inaccurate, causing some memory wastage and maybe also worse tail latencies? Jann Horn
2021-01-12 0:27 ` Roman Gushchin
2021-01-12 16:35 ` Christoph Lameter
2021-01-14 9:27 ` Vlastimil Babka
2021-01-18 11:03 ` Michal Hocko
2021-01-18 15:46 ` Christoph Lameter
2021-01-18 16:07 ` Michal Hocko
2021-01-13 19:14 ` Vlastimil Babka
2021-01-13 22:37 ` Jann Horn
2021-01-14 9:04 ` Christoph Lameter [this message]
2021-01-21 17:21 ` Vlastimil Babka
2021-01-21 17:21 ` [RFC 1/2] mm, vmscan: add priority field to struct shrink_control Vlastimil Babka
2021-01-21 17:21 ` [RFC 2/2] mm, slub: add shrinker to reclaim cached slabs Vlastimil Babka
2021-01-22 0:48 ` Roman Gushchin
2021-01-26 12:06 ` Vlastimil Babka
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