linux-kernel - Re: [PATCH -next] init/main: Init jump_labels before they are used to build zonelists

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Date:   Thu, 19 Jan 2017 09:56:33 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Stafford Horne <shorne@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Jessica Yu <jeyu@...hat.com>, Petr Mladek <pmladek@...e.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Yang Shi <yang.shi@...aro.org>, Tejun Heo <tj@...nel.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Yaowei Bai <baiyaowei@...s.chinamobile.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH -next] init/main: Init jump_labels before they are used
 to build zonelists

On Thu, Jan 19, 2017 at 09:28:28AM +0100, Vlastimil Babka wrote:
> On 01/17/2017 09:49 PM, Vlastimil Babka wrote:
> > On 17.1.2017 21:34, Andrew Morton wrote:
> >>>>
> >>>> Will you be able to look into that? Openrisc doesnt have jump_label
> >>>> support, so its no issue at the moment.
> >>>>
> >>>> Archs that do have it:
> >>>>
> >>>> arch/arm64/Kconfig:     select HAVE_ARCH_JUMP_LABEL
> >>>> arch/mips/Kconfig:      select HAVE_ARCH_JUMP_LABEL
> >>>> arch/s390/Kconfig:      select HAVE_ARCH_JUMP_LABEL
> >>>> arch/sparc/Kconfig:     select HAVE_ARCH_JUMP_LABEL if SPARC64
> >>>> arch/tile/Kconfig:      select HAVE_ARCH_JUMP_LABEL
> >>>> arch/x86/Kconfig:       select HAVE_ARCH_JUMP_LABEL
> >>>> arch/arm/Kconfig:       select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
> >>>> arch/powerpc/Kconfig:   select HAVE_ARCH_JUMP_LABEL
> >>>>
> >>>> I looked at a few (arm, tile) and I dont see their arch_jump_label_transform*
> >>>> implementations depending on global state like ideal_nops from x86. They
> >>>> should be ok.
> >>>
> >>> Thanks, I'll try.
> >>>
> >>>> If no time, Should you change your patch to not use static keys for
> >>>> build_all_zonelists at least?
> >>>
> >>> Yes that would be uglier but possible if I find issues or I'm not
> >>> confident enough with the auditing...
> >>
> >> We could just revert f5adbdff6a1c40e19 ("mm, page_alloc: convert
> >> page_group_by_mobility_disable to static key")?
> > 
> > That's a -next commit id, as the patch is in mmotm. I'll ask for removal if I
> > don't have a fix soon, but if you or somebody else prefers to do that ASAP, it
> > can be re-added later with a fix.
> 
> OK I think that we just drop the patch [1] from mmotm. Mel told me the
> benefit was marginal, and also the last move of jump_label_init() caused
> problems for several releases.
> 

Note that it's not guaranteed to cause any problems this time. If
jump_label_init can go ahead without the page allocator being fully up
and running then it may be ok.

-- 
Mel Gorman
SUSE Labs