linux-kernel - Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work

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: <CAOh2x=nbisppmuBwfLWndyCPKem1N_KzoTxyAYcQuL77T_bJfw@mail.gmail.com>
Date:	Sat, 28 Mar 2015 09:48:28 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, hannes@...xchg.org,
	Christoph Lameter <cl@...ux.com>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	vinmenon@...eaurora.org, shashim@...eaurora.org,
	Michal Hocko <mhocko@...e.cz>, mgorman@...e.de,
	dave@...olabs.net, koct9i@...il.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work

On Fri, Mar 27, 2015 at 3:00 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, Mar 27, 2015 at 10:16:13AM +0100, Peter Zijlstra wrote:

>> So the issue seems to be that we need base->running_timer in order to
>> tell if a callback is running, right?
>>
>> We could align the base on 8 bytes to gain an extra bit in the pointer
>> and use that bit to indicate the running state. Then these sites can
>> spin on that bit while we can change the actual base pointer.
>
> Even though tvec_base has ____cacheline_aligned stuck on, most are
> allocated using kzalloc_node() which does not actually respect that but
> already guarantees a minimum u64 alignment, so I think we can use that
> third bit without too much magic.

Right. So what I tried earlier was very much similar to you are suggesting.
The only difference was that I haven't made much attempts towards
saving memory.

But Thomas didn't like it for sure and I believe that Rant will hold true for
what you are suggesting as well, isn't it ?

http://lists.linaro.org/pipermail/linaro-kernel/2013-November/008866.html
--
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/