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]

Date:	Mon, 30 Mar 2015 17:14:31 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	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, 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 Mon, Mar 30, 2015 at 05:08:18PM +0200, Michal Hocko wrote:
> On Sat 28-03-15 10:53:22, Peter Zijlstra wrote:
> [...]
> > Alternatively the thing hocko suggests is an utter fail too. You cannot
> > stuff that into hardirq context, that's insane.
> 
> I guess you are referring to
> http://article.gmane.org/gmane.linux.kernel.mm/127569, right?
> 
> Why cannot we do something like refresh_cpu_vm_stats from the IRQ
> context?  Especially the first zone stat part.

Big machines have big zone counts. There are machines with >200 nodes.
Although with the current trend of bigger nodes, the number of nodes
seems to come down as well. Still.

> The per-cpu pagesets is
> more costly and it would need a special treatment, alright. A simple
> way would be to splice the lists from the per-cpu context and then free
> those pages from the kthread context.
> 
> I am still wondering why those two things were squashed into a single
> place. Why kswapd is not doing the pcp cleanup?

Probably because they could be. The problem with kswapd is that its per
node, not per cpu.
--
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/