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Date: Fri, 2 Dec 2011 12:42:52 +0400
From: Lev Serebryakov <lev@FreeBSD.org>
Organization: FreeBSD
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To: Kirk McKusick <mckusick@mckusick.com>
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References: <20111125110235.GB1642@garage.freebsd.pl>
	<201112020236.pB22aQi6059579@chez.mckusick.com>
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Cc: freebsd-fs@freebsd.org, Pawel Jakub Dawidek <pjd@freebsd.org>
Subject: Re: Does UFS2 send BIO_FLUSH to GEOM when update metadata (with
	softupdates)?
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Hello, Kirk.
You wrote 2 =E4=E5=EA=E0=E1=F0=FF 2011 =E3., 6:36:26:

> The one place where a synchronous write (bwrite) is used is when the
> completion of a particular I/O is needed to make progress on many other
> things (usually an update to the SUJ log) in which case SU will force a
> flush on that I/O (e.g., bwrite it) to hasten it along.
  So, it will be great, if SU will mark such writes additionally :) It
could help sometimes -- even if lower layers will not lie about
complete writes, it looks that SUJ could work better if such
really-critical writes will not delayed at all (even for 30 seconds,
which are Ok for all pother SU writes, as you stated earlier).

--=20
// Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>