linux-kernel - Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace

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Message-ID: <20160915092729.GA28075@gmail.com>
Date:   Thu, 15 Sep 2016 11:27:29 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jann Horn <jann@...jh.net>,
        Andrew Lutomirski <luto@...nel.org>,
        Brian Gerst <brgerst@...il.com>, Peter Anvin <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in
 save_stack_trace_tsk()


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> It absolutely is - compared to the vmalloc costs. Andy has quite noticeable 
> slowdowns without the stack reuse - and the stack reuse requires the delayed 
> freeing. With the stack reuse, fork/exit actually sped up.

Ok, great, that's convincing!

I'm still applying it two-phase and I'll wait for v2 of the second half of the 
series, to have the fix Josh alluded to.

Thanks,

	Ingo