netdev - Re: [PATCH] nohz: prevent tilegx network driver interrupts

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] [day] [month] [year] [list]

Message-ID: <55AD7310.40000@ezchip.com>
Date:	Mon, 20 Jul 2015 18:15:44 -0400
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nohz: prevent tilegx network driver interrupts

On 07/20/2015 05:49 PM, Frederic Weisbecker wrote:
> On Mon, Jul 20, 2015 at 05:22:12PM -0400, Chris Metcalf wrote:
>> On 07/11/2015 10:30 AM, Frederic Weisbecker wrote:
>>> On Fri, Jul 10, 2015 at 03:05:02PM -0400, Chris Metcalf wrote:
>>>> The tilegx chips typically don't do cpu offlining anyway, since
>>>> we've never really found a usecase, so whatever you boot with
>>>> you always have available.  We do have support for a bare-metal
>>>> mode which you can run on some of the cores, so you may start
>>>> with fewer than cpu_possible actually running, but it will always
>>>> be that same set of cores.
>>> And that bare metal mode runs out of Linux?
>> The bare metal environment runs on cpus that have been marked
>> as unavailable to Linux, so Linux just sees them as permanently
>> offlined.  There is a BME driver (which we haven't upstreamed,
>> since the BME isn't upstreamed either) that arranges to share
>> memory between the BME and Linux.
>>
>> I don't think that many customers are using the BME in any
>> case.  We push all of them towards using our dataplane mode
>> instead, since it almost always works just as well from a
>> performance perspective, and is easier to develop code for.
> So bare metal mode is different than dataplane mode, right?
> Where bare metal mode offlines the CPU and IIUC dataplane mode
> instead uses CPUs that are available to Linux, just isolated
> with nohz and various affinity stuff, right?

Yes, exactly.  Cores running the bare metal environment are
NOT running Linux at all, just talking directly to the Tilera
hypervisor.

-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html