linux-kernel - Re: weird throughput on write to SATA disk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1223936351.3947.41.camel@duo>
Date:	Tue, 14 Oct 2008 00:19:11 +0200
From:	kenneth johansson <ken@...jo.org>
To:	Grant Grundler <grundler@...gle.com>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: weird throughput on write to SATA disk

On Mon, 2008-10-13 at 14:34 -0700, Grant Grundler wrote:
> On Mon, Oct 13, 2008 at 2:22 PM, kenneth johansson <ken@...jo.org> wrote:
> > On Mon, 2008-10-13 at 14:07 -0700, Grant Grundler wrote:
> >> On Mon, Oct 13, 2008 at 12:19 PM, kenneth johansson <ken@...jo.org> wrote:
> >> > When writing data to /dev/sdb (that is the whole disk and no filesystem)
> >> > it starts out ok around 100MB/sec but soon end up doing considerably
> >> > worse. For prolonged times lasting several minutes it hovers in the
> >> > 20-30MB/sec.
> >>
> >> Is the application using "O_DIRECT"?
> >
> > no just open then write no fancy stuff
> >
> >> If not, could be issue with how VM writeback is (not) working.
> >
> > the access pattern is the simplest possible. Is there any knobs I could
> > try to adjust.
> >
> >> Can you reproduce this using fio or even "dd"?
> >> (See git://git.kernel.dk/fio)
> >
> > dd is having the same effect.
> 
> Can you try "dd oflag=direct if=/dev/null of=/dev/sdb bs=64k"?

I changed to use O_DIRECT and it's much more consistent now. 69-75 with
74 about 95% of the time. the disk is supposed to have 105 115 sustained
data rate. 



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/