From: Mel Gorman <mgorman@techsingularity.net>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Linux-MM <linux-mm@kvack.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored on the per-cpu lists
Date: Tue, 1 Jun 2021 13:45:33 +0100 [thread overview]
Message-ID: <20210601124533.GU30378@techsingularity.net> (raw)
In-Reply-To: <20210531172338.2e7cb070@carbon>
On Mon, May 31, 2021 at 05:23:38PM +0200, Jesper Dangaard Brouer wrote:
> On Mon, 31 May 2021 13:04:12 +0100
> Mel Gorman <mgorman@techsingularity.net> wrote:
>
> > The per-cpu page allocator (PCP) only stores order-0 pages. This means
> > that all THP and "cheap" high-order allocations including SLUB contends
> > on the zone->lock. This patch extends the PCP allocator to store THP and
> > "cheap" high-order pages. Note that struct per_cpu_pages increases in
> > size to 256 bytes (4 cache lines) on x86-64.
> >
> > Note that this is not necessarily a universal performance win because of
> > how it is implemented. High-order pages can cause pcp->high to be exceeded
> > prematurely for lower-orders so for example, a large number of THP pages
> > being freed could release order-0 pages from the PCP lists. Hence, much
> > depends on the allocation/free pattern as observed by a single CPU to
> > determine if caching helps or hurts a particular workload.
> >
> > That said, basic performance testing passed. The following is a netperf
> > UDP_STREAM test which hits the relevant patches as some of the network
> > allocations are high-order.
>
> This series[1] looks very interesting! I confirm that some network
> allocations do use high-order allocations. Thus, I think this will
> increase network performance in general, like you confirm below:
>
Would you be able to do a small test on a real high-speed network? It's
something I can do easily myself in a few weeks but I do not have testbed
readily available at the moment. It's ok if you do not have the time,
it would just be nice if I could include independent results in the
changelog if the results are positive. Alternatively, a negative result
would mean going back to the drawing board :)
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-06-01 12:45 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-31 12:04 [RFC PATCH 0/2] Allow high order pages to be stored on PCP Mel Gorman
2021-05-31 12:04 ` [PATCH 1/2] mm/page_alloc: Move free_the_page Mel Gorman
2021-05-31 12:04 ` [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored on the per-cpu lists Mel Gorman
2021-05-31 15:23 ` Jesper Dangaard Brouer
2021-06-01 12:45 ` Mel Gorman [this message]
2021-06-02 13:53 ` Jesper Dangaard Brouer
2021-06-03 8:46 [PATCH 0/2] Allow high order pages to be stored on PCP Mel Gorman
2021-06-03 8:46 ` [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored on the per-cpu lists Mel Gorman
2021-06-03 11:12 ` Vlastimil Babka
2021-06-03 12:34 ` Mel Gorman
2021-06-03 13:04 ` Vlastimil Babka
2021-06-03 14:22 [PATCH 0/2] Allow high order pages to be stored on PCP v2 Mel Gorman
2021-06-03 14:22 ` [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored on the per-cpu lists Mel Gorman
2021-06-09 18:30 ` Zi Yan
2021-06-10 11:18 ` Mel Gorman
2021-06-10 11:40 ` Zi Yan
2021-06-10 22:59 ` Andrew Morton
2021-06-11 0:38 ` Stephen Rothwell
2021-06-11 8:10 ` Mel Gorman
2021-06-11 8:34 ` Mel Gorman
2021-06-11 12:17 ` Zi Yan
2021-06-11 13:58 ` Mel Gorman
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