linux-kernel - Re: [PATCH 7/7] x86,idle: do not leave mm in idle state

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1529698739.7898.206.camel@surriel.com>
Date:   Fri, 22 Jun 2018 16:18:59 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Mike Galbraith <efault@....de>, songliubraving@...com,
        kernel-team <kernel-team@...com>
Subject: Re: [PATCH 7/7] x86,idle: do not leave mm in idle state

On Fri, 2018-06-22 at 09:01 -0700, Andy Lutomirski wrote:
> Hmm, fair enough.  I think a better heuristic would be if the
> estimated idle duration is more than, say, 10ms.  I *think* the code
> has been cleaned up enough that this is easy now.  (Using time
> instead
> of C6 will make it a lot less dependent on which idle driver is in
> use.)

This particular bit of code is only in intel_idle
though, and not every cpuidle governor estimates
an idle duration, nor does it get passed up the
stack (presumably because it not always exists).

I will just drop this patch for now, and see if
adding back in the patch that skips manipulation
of the mm_cpumask(&init_mm), since that might make
leave_mm() a little cheaper.

We would still have excess manipulation of the
bitmask when re-entering the task from what should
have been lazy TLB mode, but total cache line
contention would likely still be down from where
it is before that patch.

-- 
All Rights Reversed.
Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)