From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
linux-mm@kvack.org, Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH 3/4] kernel/fork: switch vmapped stack callation to __vmalloc_area()
Date: Wed, 21 Feb 2018 10:23:12 +0300 [thread overview]
Message-ID: <d636d1cb-88d9-8474-d5bc-fb2994108919@yandex-team.ru> (raw)
In-Reply-To: <20180220161634.517598ec63ec4a785c4c81cc@linux-foundation.org>
On 21.02.2018 03:16, Andrew Morton wrote:
> On Tue, 23 Jan 2018 16:57:21 +0300 Konstantin Khlebnikov <khlebnikov@yandex-team.ru> wrote:
>
>> # stress-ng --clone 100 -t 10s --metrics-brief
>> at 32-core machine shows boost 35000 -> 36000 bogo ops
>>
>> Patch 4/4 is a kind of RFC.
>> Actually per-cpu cache of preallocated stacks works faster than buddy allocator thus
>> performance boots for it happens only at completely insane rate of clones.
>>
>
> I'm not really sure what to make of this patchset. Is it useful in any
> known real-world use cases?
Not yet. Feel free to ignore last patch.
>
>> + This option neutralize stack overflow protection but allows to
>> + achieve best performance for syscalls fork() and clone().
>
> That sounds problematic, but perhaps acceptable if the fallback only
> happens rarely.
>
> Can this code be folded into CONFIG_VMAP_STACk in some cleaner fashion?
> We now have options for non-vmapped stacks, vmapped stacks and a mix
> of both.
>
> And what about this comment in arch/Kconfig:VMAP_STACK:
>
> This is presently incompatible with KASAN because KASAN expects
> the stack to map directly to the KASAN shadow map using a formula
> that is incorrect if the stack is in vmalloc space.
>
>
> So VMAP_STACK_AS_FALLBACK will intermittently break KASAN?
>
All of this (including CONFIG_VMAP_STACK) could be turned into boot option.
I think this would be a best solution.
next prev parent reply other threads:[~2018-02-21 7:23 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-23 10:55 [PATCH 1/4] vmalloc: add vm_flags argument to internal __vmalloc_node() Konstantin Khlebnikov
2018-01-23 10:55 ` [PATCH 2/4] vmalloc: add __vmalloc_area() Konstantin Khlebnikov
2018-01-23 10:55 ` [PATCH 3/4] kernel/fork: switch vmapped stack callation to __vmalloc_area() Konstantin Khlebnikov
2018-01-23 13:57 ` Konstantin Khlebnikov
2018-02-21 0:16 ` Andrew Morton
2018-02-21 7:23 ` Konstantin Khlebnikov [this message]
2018-02-21 16:35 ` Andy Lutomirski
2018-01-23 10:55 ` [PATCH 4/4] kernel/fork: add option to use virtually mapped stacks as fallback Konstantin Khlebnikov
2018-02-21 15:42 ` Use higher-order pages in vmalloc Matthew Wilcox
2018-02-21 16:11 ` Andy Lutomirski
2018-02-21 16:50 ` Matthew Wilcox
2018-02-21 16:16 ` Dave Hansen
2018-02-21 17:01 ` Matthew Wilcox
2018-02-22 6:59 ` Michal Hocko
2018-02-22 12:22 ` Matthew Wilcox
2018-02-22 13:36 ` Michal Hocko
2018-02-22 19:01 ` Andy Lutomirski
2018-02-22 19:19 ` Dave Hansen
2018-02-22 19:27 ` Andy Lutomirski
2018-02-22 19:36 ` Dave Hansen
2018-02-23 12:13 ` Michal Hocko
2018-03-01 18:16 ` Eric Dumazet
2018-02-21 12:24 ` [PATCH 1/4] vmalloc: add vm_flags argument to internal __vmalloc_node() Matthew Wilcox
2018-02-21 12:39 ` Andrey Ryabinin
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