linux-kernel - Re: [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority delivery mode

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: <CA+55aFx3ogOzGWZvfETgoKqoLzTc7qw6QjmouSLG4JF9aRdjig@mail.gmail.com>
Date:	Mon, 21 May 2012 11:18:04 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Alexander Gordeev <agordeev@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority
 delivery mode

On Mon, May 21, 2012 at 11:07 AM, Suresh Siddha
<suresh.b.siddha@...el.com> wrote:
>
> All the cluster members of a given x2apic cluster belong to the same
> package. These x2apic cluster id's are setup by the HW and not by the
> SW. And only one cluster (with one or multiple members of that cluster
> set) can be specified in the interrupt destination field of the routing
> table entry.

Ok, then the main question ends up being if there are enough cache or
power domains within a cluster to still worry about it.

For example, you say "package", but that can sometimes mean multiple
dies, or even just split caches that are big enough to matter
(although I can't think of any such right now on the x86 side - Core2
Duo had huge L2's, but they were shared, not split).

> Power aware interrupt routing in IVB does this. And the policy of
> whether you want the interrupt to be routed to the busy core (to save
> power) or an idle core (for minimizing the interruptions on the busy
> core) can be selected by the SW (using IA32_ENERGY_PERF_BIAS MSR).

Sounds like we definitely would want to support this at least in the
IVB timeframe then.

But I do agree with Ingo that it would be really good to actually see
numbers (and no, I don't mean "look here, now the irq's are nicely
spread out", but power and/or performance numbers showing that it
actually helps something).

                   Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/