|To:||Dave Chinner <david@xxxxxxxxxxxxx>|
|Subject:||Re: [PATCH] [RFC] xfs: lookaside cache for xfs_buf_find|
|From:||Mark Tinguely <tinguely@xxxxxxx>|
|Date:||Mon, 09 Sep 2013 10:17:24 -0500|
|User-agent:||Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0|
On 09/08/13 20:33, Dave Chinner wrote:
From: Dave Chinner<dchinner@xxxxxxxxxx> CPU overhead of buffer lookups dominate most metadata intensive workloads. The thing is, most such workloads are hitting a relatively small number of buffers repeatedly, and so caching recently hit buffers is a good idea. Add a hashed lookaside buffer that records the recent buffer lookup successes and is searched first before doing a rb-tree lookup. If we get a hit, we avoid the expensive rbtree lookup and greatly reduce the overhead of the lookup. If we get a cache miss, then we've added an extra CPU cacheline miss into the lookup.
Interesting. The last allocated xfs_buf is placed into the hash. Might be interesting to know the hit-miss ratio on a real workload. --Mark.
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