2013-07-16 19:10:45

by Uwe Kleine-König

[permalink] [raw]
Subject: configurable partial slab support on UP

Hello,

(sorry for breaking the mail threading, but I failed to find the right
mail to reply to.)

while doing make oldconfig on an !SMP config using 3.11-rc1 I was asked
if I want CONFIG_SLUB_CPU_PARTIAL. AFAICT this setting only affects SMP
machines? If so I suggest to make the choice depend on SMP and treat the
!SMP case as CONFIG_SLUB_CPU_PARTIAL=n.

This was introduced in commit
345c905 (slub: Make cpu partial slab support configurable)

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-K?nig |
Industrial Linux Solutions | http://www.pengutronix.de/ |


2013-07-17 07:03:09

by Pekka Enberg

[permalink] [raw]
Subject: Re: configurable partial slab support on UP

On Tue, Jul 16, 2013 at 10:10 PM, Uwe Kleine-K?nig
<[email protected]> wrote:
> Hello,
>
> (sorry for breaking the mail threading, but I failed to find the right
> mail to reply to.)
>
> while doing make oldconfig on an !SMP config using 3.11-rc1 I was asked
> if I want CONFIG_SLUB_CPU_PARTIAL. AFAICT this setting only affects SMP
> machines? If so I suggest to make the choice depend on SMP and treat the
> !SMP case as CONFIG_SLUB_CPU_PARTIAL=n.
>
> This was introduced in commit
> 345c905 (slub: Make cpu partial slab support configurable)

The per-CPU partial list is used on UP machines as well so the config
option does affect them. Whether or not they should be used is another
topic entirely. Christoph, Joonsoo?

Pekka

Subject: Re: configurable partial slab support on UP

On Wed, 17 Jul 2013, Pekka Enberg wrote:

> > while doing make oldconfig on an !SMP config using 3.11-rc1 I was asked
> > if I want CONFIG_SLUB_CPU_PARTIAL. AFAICT this setting only affects SMP
> > machines? If so I suggest to make the choice depend on SMP and treat the
> > !SMP case as CONFIG_SLUB_CPU_PARTIAL=n.

Sounds ok.
> >
> > This was introduced in commit
> > 345c905 (slub: Make cpu partial slab support configurable)
>
> The per-CPU partial list is used on UP machines as well so the config
> option does affect them. Whether or not they should be used is another
> topic entirely. Christoph, Joonsoo?

cpu partial pages are used to avoid contention which does not exist in the
UP case. We can simply default to off for UP.