From: Pavel Machek <pavel@suse.cz>
To: Andrew Morton <akpm@zip.com.au>
Cc: kernel list <linux-kernel@vger.kernel.org>
Subject: Re: Sync over loop devices takes ages? [2.4.17]
Date: Thu, 28 Feb 2002 21:12:48 +0100 [thread overview]
Message-ID: <20020228201248.GA20466@atrey.karlin.mff.cuni.cz> (raw)
In-Reply-To: <20020228095955.GH774@elf.ucw.cz> <3C7E716E.9DC59B12@zip.com.au>
In-Reply-To: <3C7E716E.9DC59B12@zip.com.au>
Hi!
> > I have a script (attached). At one point it tries to do sync... That
> > sync take a long time, with disk mostly unused.
>
> When doing (say) ext2-on-loop-on-ext2 you should always ensure
> that the blocksize for the topmost filesystem is the same as
> the one underneath. So probably you wanted `mkfs.ext2 -b 4096'.
>
> If you have a 1k blocksize filesystem loop-mounted on a 4k blocksize
> filesystem, every write of a 1k block requires a read of the underlying
> 4k block. Which is excrutiatingly slow.
Oh, but I *want* to do 1k filesystem test!
Performance seems okay in 2.4.19-pre?aa?.... And even 2.4.18 is
slightly faster. [BTW it is fully cached (100MB test on 256MB machine)
so 4k reads should not be such a big problem.]
Pavel
--
Casualities in World Trade Center: ~3k dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.
prev parent reply other threads:[~2002-02-28 20:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-28 9:59 Pavel Machek
2002-02-28 11:52 ` Bjorn Wesen
2002-02-28 18:05 ` Andrew Morton
2002-02-28 20:12 ` Pavel Machek [this message]
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