From: Cyril Hrubis <chrubis@suse.cz>
To: ltp@lists.linux.it
Subject: [LTP] [PATCH] readahead02: estimate max readahead size
Date: Mon, 10 Oct 2016 17:03:52 +0200 [thread overview]
Message-ID: <20161010150352.GC1684@rei> (raw)
In-Reply-To: <141170940.52106.1476110506518.JavaMail.zimbra@redhat.com>
Hi!
> > I've tried this on the /tmp on Btrfs and got max_ra_estimage nearly ten times
> > greater than the sysfs value. But apart from that the measured times are
> > pretty
> > much comparable with the previous version, which suggests that maximal
> > readahead size on Btrfs is set to ~4M and the limit per device is not
> > applicable.
> >
> > Did you get the estimate close to the value of the sysfs file in your
> > environment?
>
> I do (on 4.8 x86 KVM guest):
> # cat /sys/devices/virtual/bdi/253:1/read_ahead_kb
> 4096
> readahead02 0 TINFO : max ra estimate: 4145152
>
> Are you using upstream kernel or a patched one?
That is Btrfs on SLES12-SP2 RC with kernel 4.4.21, but it seems to be
pretty much Btrfs specific. If I point TMPDIR to ext3 fs I got estimated
ra 507904 while the read_ahead_kb for the device is set to 512.
--
Cyril Hrubis
chrubis@suse.cz
prev parent reply other threads:[~2016-10-10 15:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-10 11:31 [LTP] [PATCH] readahead02: estimate max readahead size Jan Stancek
2016-10-10 14:16 ` Cyril Hrubis
2016-10-10 14:41 ` Jan Stancek
2016-10-10 15:03 ` Cyril Hrubis [this message]
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