Re: [PATCH] fs/buffer.c: make bh_lru_install() more efficient

[Eric Biggers <ebiggers3@gmail.com>]

On Thu, Dec 29, 2016 at 01:34:45PM -0600, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.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@google.com>

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

- Eric