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

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Message-ID: <20170603135634.GA18453@linux-zmni.DHCP>
Date:   Sat, 3 Jun 2017 21:56:36 +0800
From:   Sean Fu <fxinrong@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     ebiggers@...gle.com
Subject: Re: [PATCH] fs/buffer.c: make bh_lru_install() more efficient

On Sat, Mar 25, 2017 at 08:34:30PM -0700, Eric Biggers wrote:
> 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
IMO, It is great patch.
Could you please share your microbenchmark steps?
I wanna take a deep look at it.