linux-kernel - Re: [PATCH] fs/buffer.c: make bh_lru

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Message-ID: <20170326033430.GA20915@zzz>
Date:   Sat, 25 Mar 2017 20:34:30 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH] fs/buffer.c: make bh_lru_install() more efficient

On Thu, Dec 29, 2016 at 01:34:45PM -0600, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> To install a buffer_head into the cpu's LRU queue, bh_lru_install()
> would construct a new copy of the queue and then memcpy it over the real
> queue.  But it's easily possible to do the update in-place, which is
> faster and simpler.  Some work can also be skipped if the buffer_head
> was already in the queue.
> 
> As a microbenchmark I timed how long it takes to run sb_getblk()
> 10,000,000 times alternating between BH_LRU_SIZE + 1 blocks.
> Effectively, this benchmarks looking up buffer_heads that are in the
> page cache but not in the LRU:
> 
> 	Before this patch: 1.758s
> 	After this patch: 1.653s
> 
> This patch also removes about 350 bytes of compiled code (on x86_64),
> partly due to removal of the memcpy() which was being inlined+unrolled.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Ping?  Al, do you have any interest in taking this patch?

- Eric