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To: Don Lewis <truckman@FreeBSD.org>
Subject: Re: access to hard drives is "blocked" by writes to a flash drive
In-reply-to: <201303040712.r247CejP008718@gw.catspoiler.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <201303040712.r247CejP008718@gw.catspoiler.org>
Date: Mon, 04 Mar 2013 13:44:30 +0000
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Cc: kostikbel@gmail.com, deeptech71@gmail.com, freebsd-current@FreeBSD.org,
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In message <201303040712.r247CejP008718@gw.catspoiler.org>, Don Lewis writes:

>Prior to 231160, the syncer thread would call sync_vnode() for the
>syncer vnode of each mountpoint every 30 seconds [...]

I agree that the lemming syncer is better, but the fundamental mistake of
only having one syncer thread is probably the root-cause in this case:
One camera-grade flash syncing may take (a lot) more than 30 seconds.

One mountpoint having trouble (of whatever kind) should not affect
the rest of the mountpoints.

I'm not sure if the syncer is untangled enough that we can have
per mount-point threads yet, but as soon as we can, we should do that.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.