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Date:      Sun, 22 Nov 2015 22:05:35 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-hackers@FreeBSD.org
Subject:   [Bug 204716] boot loader bcache is trashed by larger sequential reads from zfs/ufs
Message-ID:  <bug-204716-9315-MGlklAn9n1@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-204716-9315@https.bugs.freebsd.org/bugzilla/>
References:  <bug-204716-9315@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204716

--- Comment #3 from Toomas Soome <tsoome@me.com> ---
well, of course it really depends on other interfaces, I actually did something
more about bcache - instead of LRU, I use it as hash table, and in fact did
make it a bit larger for test purposes.

zfs boot to beastie menu:
cache blocks: 8192
cache blocksz: 512
3906 ops  1533 bypasses  2281 hits  559 misses  6 flushes

few / directory listings and:
cache blocks: 8192
cache blocksz: 512
10110 ops  4473 bypasses  5754 hits  569 misses  6 flushes

same with illumos ufs:
cache blocks: 8192
cache blocksz: 512
1018 ops  297 bypasses  6636 hits  594 misses  6 flushes

few / directory listings and:
cache blocks: 8192
cache blocksz: 512
1564 ops  411 bypasses  13228 hits  914 misses  6 flushes

so, it can provide some use still - from this trivial sample, especially with
ufs. but once again - this sample is with hash table and without 2sec TTL
check.

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