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Bug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x

Started byHolger Levsen <holger@layer-acht.org>
First post2017-06-28 22:00 +0200
Last post2017-06-29 02:30 +0200
Articles 4 — 2 participants

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  Bug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x Holger Levsen <holger@layer-acht.org> - 2017-06-28 22:00 +0200
    Bug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x Ben Hutchings <ben@decadent.org.uk> - 2017-06-28 23:40 +0200
      Bug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x Holger Levsen <holger@layer-acht.org> - 2017-06-29 01:30 +0200
        Bug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x Holger Levsen <holger@layer-acht.org> - 2017-06-29 02:30 +0200

#58195 — Bug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x

FromHolger Levsen <holger@layer-acht.org>
Date2017-06-28 22:00 +0200
SubjectBug#866314: linux-image-4.9.0-3-686-pae: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x
Message-ID<tXri1-1Hi-5@gated-at.bofh.it>

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package: linux-image-4.9.0-3-686-pae
version: 4.9.30-2+deb9u2
# severity: important ?
forwarded: https://bugzilla.kernel.org/show_bug.cgi?id=196157

Hi,

upon upgrading the i386 build nodes for tests.reproducible-builds.org to Stretch
I noticed a huge performance loss, which I could "fix" by installing 
linux-image-4.9.0-3-amd64:amd64 (version 4.9.30-2+deb9u2 too).
(which btw is a nice example for Multiarchs's usefulness…)

Today Vagrant pointed me to https://bugzilla.kernel.org/show_bug.cgi?id=196157
which is the upstream issue tracking this.

I'm filing this bug for the benefit of other Debian users and for myself to
benefit from the BTS subscription and tracking features…

We want to run half of our i386 build nodes with a 32 bit kernel and the other
half with an 64 bit kernel to test reproducibility under this variation, so
I'm really looking forward to see this bug fixed soon. Other people can
probably just keep running the amd64 kernel, thus I've decided for normal 
severity for this issue.

Thanks for maintaining src:linux!


-- 
cheers,
	Holger

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#58199

FromBen Hutchings <ben@decadent.org.uk>
Date2017-06-28 23:40 +0200
Message-ID<tXsQO-v0-17@gated-at.bofh.it>
In reply to#58195

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On Wed, 2017-06-28 at 19:53 +0000, Holger Levsen wrote:
> package: linux-image-4.9.0-3-686-pae
> version: 4.9.30-2+deb9u2
> # severity: important ?

I would say only 'normal', because this isn't a sensible configuration.

[...]
> We want to run half of our i386 build nodes with a 32 bit kernel and the other
> half with an 64 bit kernel to test reproducibility under this variation, so
> I'm really looking forward to see this bug fixed soon. Other people can
> probably just keep running the amd64 kernel, thus I've decided for normal 
> severity for this issue.

Why don't you assign a smaller amount of RAM to the 32-bit VMs?  Are
there packages that need this much to build?

Ben.

-- 
Ben Hutchings
Absolutum obsoletum. (If it works, it's out of date.) - Stafford Beer

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#58202

FromHolger Levsen <holger@layer-acht.org>
Date2017-06-29 01:30 +0200
Message-ID<tXuzh-1Do-5@gated-at.bofh.it>
In reply to#58199

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On Wed, Jun 28, 2017 at 10:35:39PM +0100, Ben Hutchings wrote:
> I would say only 'normal', because this isn't a sensible configuration.
 
I was saying today that there are probably 100 people running i386 with i386
kernels with more than 16gb ram in the world. And then corrected myself to
"1000"…

;-)

> Why don't you assign a smaller amount of RAM to the 32-bit VMs?  Are
> there packages that need this much to build?
 
because there are up to ten builds running simulataneously on these machines.
5 on average, and usually between 3 and 7 I'd say…

And hey, it used to work nicely.

(As a workaround I plan to use 8 machines with 15gb ram instead of 4 with 35…)


-- 
cheers,
	Holger

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#58203

FromHolger Levsen <holger@layer-acht.org>
Date2017-06-29 02:30 +0200
Message-ID<tXvvk-rh-1@gated-at.bofh.it>
In reply to#58202

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On Wed, Jun 28, 2017 at 11:22:06PM +0000, Holger Levsen wrote:
> (As a workaround I plan to use 8 machines with 15gb ram instead of 4 with 35…)

actually this wont work here, there are not enough storage ressources to run
8 instead of 4 machines…


-- 
cheers,
	Holger

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