From: Douglas Gilbert <dougg@torque.net>
To: linux-kernel@vger.kernel.org, matthias.andree@gmx.de
Subject: Re: 2.4: high system load with SG_IO on IDE-SCSI: PIO?
Date: Mon, 10 Mar 2003 15:35:50 +1000 [thread overview]
Message-ID: <3E6C2436.1000007@torque.net> (raw)
Matthias Andree wrote:
> I have seen readcd ("sg driver 3.2.0") use 96% system time
> for a readcd -c2scan on IDE-SCSI (ATAPI CD-ROM, Plextor
> PX-4824TA 1.04, UDMA/33), Linux 2.4.19+SuSE patches
> (k_athlon-2.4.19-167).
>
> ...
> ioctl(3, 0x2285, 0xbfffec20) = 0
> ...
>
> The same application on a real SCSI-device with SCSI host
> adaptor (aic7xxx FWIW) is way below 5% system CPU time.
>
> Might SG_IO use PIO on ATAPI CD-ROMs? If so, are there
> patches to enable DMA? Is this at all possible with SG_IO?
> I find 96% system load is way too high for modern hardware.
> (Duron/700 that is, VIA 82C686a).
SG_IO is an ioctl in the sg driver that issues scsi commands
and waits for a response. The route from sg is through the
scsi mid level and via ide-scsi to the ide subsystem. Nothing
in the SG_IO ioctl interface addresses ATA DMA and PIO settings.
They can be changed via the hdparm ** command.
The experience from the early 2.4 series was that the ide
subsystem was too aggressive in its DMA settings for CD/DVD
burners. [My experience with scsi devices is that disks have
much better target implementations (i.e. more robust) than
CD/DVD devices and scanners.] Later versions of the 2.4 series
are a lot more conservative in their speed treatment of ATAPI
devices. The robustness comes at the expense of system load.
** Even though a CD writer appears as /dev/scd0 with ide-scsi
appropriately configured, the hdparm command can still be used
on /dev/hdd (for example, if the writer is the slave on the
second IDE bus).
Doug Gilbert
next reply other threads:[~2003-03-10 5:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-10 5:35 Douglas Gilbert [this message]
2003-03-10 11:31 ` 2.4: high system load with SG_IO on IDE-SCSI: PIO? Matthias Andree
-- strict thread matches above, loose matches on Subject: below --
2003-03-09 14:49 Matthias Andree
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3E6C2436.1000007@torque.net \
--to=dougg@torque.net \
--cc=linux-kernel@vger.kernel.org \
--cc=matthias.andree@gmx.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.