linux-kernel - [RFC PATCH 0/4] Fast noirq bulk page allocator

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Date:   Wed,  4 Jan 2017 11:10:45 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [RFC PATCH 0/4] Fast noirq bulk page allocator

This series is motivated by a conversation led by Jesper Dangaard Brouer at
the last LSF/MM proposing a generic page pool for DMA-coherent pages. Part of
his motivation was due to the overhead of allocating multiple order-0 that
led some drivers to use high-order allocations and splitting them which
can be very slow if high-order pages are unavailable. This long-overdue
series aims to show that raw bulk page allocation can be achieved relatively
easily without introducing a completely new allocator. A new generic page
pool allocator would then ideally focus on just the DMA-coherent part.

The first two patches in the series restructure the allocator such that
it's relatively easy to build a bulk page allocator. The third patch
alters the per-cpu alloctor to make it exclusive to !irq requests. This
cuts allocation/free overhead by roughly 30% but it may not be noticable
to anyone other than users of high-speed networks (I'm not one). The
fourth patch introduces a bulk page allocator with no in-kernel users as
an example for Jesper and others who want to build a page allocator for
DMA-coherent pages.  It hopefully is relatively easy to modify this API
and the one core function to get the semantics they require.  Note that
Patch 3 is not required for patch 4 but it may be desirable if the bulk
allocations happen from !IRQ context.

 include/linux/gfp.h |  23 ++++
 mm/page_alloc.c     | 329 ++++++++++++++++++++++++++++++++++++----------------
 2 files changed, 254 insertions(+), 98 deletions(-)

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2.11.0