Date: Sat, 21 May 2011 17:57:55 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Maxim Sobolev <sobomax@sippysoft.com> Cc: "current@freebsd.org" <current@FreeBSD.ORG> Subject: Re: Randomization in hastd(8) synchronization thread Message-ID: <20110521155755.GC3326@garage.freebsd.pl> In-Reply-To: <4DD2CEE7.1070805@sippysoft.com> References: <4DD2CEE7.1070805@sippysoft.com>
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[-- Attachment #1 --] On Tue, May 17, 2011 at 12:39:19PM -0700, Maxim Sobolev wrote: > Hi Pawel, > > I am trying to use hastd(8) over slow links and one problem is > apparent right now - current approach with synchronizing content > sequentially is not working in this case. What happens is that hastd > hits the first frequently updated block and cannot make any progress > anymore. In my case I have 30GB of dirty space to be synchronized > over just 1mbps uplink. > > The quick fix that I've applied is randomization in the block > selection code. This way eventually all least used blocks will be > synchronized, leaving only hot ones dirty. More effective approach > would be to use some kind of LRU selection algorithm, but > statistical approach would work just as good in this case. > > Please review the patch below: > > http://sobomax.sippysoft.com/activemap.c.diff Hmm, hastd keeps separate bitmap for synchronization. It is stored in am_syncmap field. Blocks that are dirtied during regular writes should not effect on synchronization bitmap and synchronization progress. -- Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://yomoli.com [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iEYEARECAAYFAk3X4QMACgkQForvXbEpPzREzQCfc7d0K2hj9txaPeZs1XpRdAQH UioAoNJx0Oee2AZL37etZ+LD4ukNPAS5 =4ZL3 -----END PGP SIGNATURE-----
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