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List:       freebsd-fs
Subject:    Looks like ZFS ARC is broken for 2.5 years. Could somebody ZFS-competent confirm or dismiss?
From:       Lev Serebryakov <lev () FreeBSD ! org>
Date:       2019-02-11 12:30:31
Message-ID: 27e55fb1-9258-ecd7-621f-86efa314c694 () FreeBSD ! org
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 One of the strongest features of ZFS is ARC algorithm for cache
management. It is still best algorithm for generic-purpose caches, for
~15 years now.

 But looks like ARC implementation in post-Solaris ZFS broken for 2.5
years now, after adding "compressed ARC". Especially, adaptions on ghost
list hits are broken.

 Look here for details:

https://reviews.freebsd.org/D19094

 Could somebody more ZFS-aware than me look at this diff? Looks like we
(and upstream, too) have huge problem with ARC effectiveness, which is
in-line with my gut feeling.

--=20
// Lev Serebryakov


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