Mailinglist Archive: opensuse (2700 mails)
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Re: [SLE] Boosting performance
- From: Ciro Iriarte <cyruspy@xxxxxxxxx>
- Date: Mon, 4 Jul 2005 22:27:13 -0400
- Message-id: <a998a0140507041927535d489b@xxxxxxxxxxxxxx>
2005/6/14, Randall R Schulz <rschulz@xxxxxxxxx>:
> Ciro,
>
> On Monday 13 June 2005 19:57, Ciro Iriarte wrote:
> > I'm running SuSE 9.2 on a Proliant DL380, was working fine, only had
> > problems copy and entire tree from one FS to another (it seems to
> > hang). The backup to tape was during 3 hours.
> > The changes made (/boot/grub/menu.lst):
> >
> > * Deleted the "desktop" kernel parameter
>
> I did this on my 9.1 system even though I am running a desktop system.
> In "desktop" mode the kernel's scheduling quantum is reduced by a
> factor of ten to create more responsiveness, but it increases
> scheduling overhead by the same factor. Given a fast enough CPU (3 GHz,
> in my case), this does not seem to impair perceived responsiveness.
>
> I'm not sure why, but my 9.3 installation did not include the "desktop"
> parameter. Maybe I removed it while installing and forgot doing so.
> Maybe it's no long enabled by default.
>
>
> > * Changed the "elevator" kernel parameter from "as" to "cfq"
>
> This relates to how disk accesses are scheduled (ordered) when there are
> multiple outstanding I/O requests pending in the kernel disk queues.
> "CFQ" stands for "completely fair queuing" and "as" stands for
> "anticipatory scheduling". As the name suggests, the "anticipatory"
> scheduling has a stronger heuristic aspect and thus has more potential
> to be thwarted by access patterns not characteristic of the patterns it
> anticipates. The AS scheduler has several tunable parameters specific
> to it, too, so it's conceivable that there are values for those
> parameters that could give you even better performance than simply
> choosing CFQ.
>
> There's some explanatory text in
> "/usr/src/linux/Documentation/block/as-iosched.txt" and
> "/usr/src/linux/Documentation/kernel-parameters.txt" that you might be
> able to use to conduct some more directed, informed experiments.
>
>
> > Now, the backups takes 1h 40 min to finish, any comments?
>
> There's no arguing with success, I'd say. At least in this case. I'd
> also venture to guess that these kernel parameters will _not_ lead to
> optimal performance during normal interactive or server loads and that
> you'll want to use them only for your backup purposes
>
> > Ciro
>
> Randall Schulz
>
> --
> Check the headers for your unsubscription address
> For additional commands send e-mail to suse-linux-e-help@xxxxxxxx
> Also check the archives at http://lists.suse.com
> Please read the FAQs: suse-linux-e-faq@xxxxxxxx
>
>
I noticed that SLES 9 comes with CFQ as the default scheduler
CI.-
> Ciro,
>
> On Monday 13 June 2005 19:57, Ciro Iriarte wrote:
> > I'm running SuSE 9.2 on a Proliant DL380, was working fine, only had
> > problems copy and entire tree from one FS to another (it seems to
> > hang). The backup to tape was during 3 hours.
> > The changes made (/boot/grub/menu.lst):
> >
> > * Deleted the "desktop" kernel parameter
>
> I did this on my 9.1 system even though I am running a desktop system.
> In "desktop" mode the kernel's scheduling quantum is reduced by a
> factor of ten to create more responsiveness, but it increases
> scheduling overhead by the same factor. Given a fast enough CPU (3 GHz,
> in my case), this does not seem to impair perceived responsiveness.
>
> I'm not sure why, but my 9.3 installation did not include the "desktop"
> parameter. Maybe I removed it while installing and forgot doing so.
> Maybe it's no long enabled by default.
>
>
> > * Changed the "elevator" kernel parameter from "as" to "cfq"
>
> This relates to how disk accesses are scheduled (ordered) when there are
> multiple outstanding I/O requests pending in the kernel disk queues.
> "CFQ" stands for "completely fair queuing" and "as" stands for
> "anticipatory scheduling". As the name suggests, the "anticipatory"
> scheduling has a stronger heuristic aspect and thus has more potential
> to be thwarted by access patterns not characteristic of the patterns it
> anticipates. The AS scheduler has several tunable parameters specific
> to it, too, so it's conceivable that there are values for those
> parameters that could give you even better performance than simply
> choosing CFQ.
>
> There's some explanatory text in
> "/usr/src/linux/Documentation/block/as-iosched.txt" and
> "/usr/src/linux/Documentation/kernel-parameters.txt" that you might be
> able to use to conduct some more directed, informed experiments.
>
>
> > Now, the backups takes 1h 40 min to finish, any comments?
>
> There's no arguing with success, I'd say. At least in this case. I'd
> also venture to guess that these kernel parameters will _not_ lead to
> optimal performance during normal interactive or server loads and that
> you'll want to use them only for your backup purposes
>
> > Ciro
>
> Randall Schulz
>
> --
> Check the headers for your unsubscription address
> For additional commands send e-mail to suse-linux-e-help@xxxxxxxx
> Also check the archives at http://lists.suse.com
> Please read the FAQs: suse-linux-e-faq@xxxxxxxx
>
>
I noticed that SLES 9 comes with CFQ as the default scheduler
CI.-
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