linux-kernel - Re: [RFC][PATCH 00/26] sched/numa

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 for Android: free password hash cracker in your pocket

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

Date:	Mon, 19 Mar 2012 14:26:34 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Dan Smith <danms@...ibm.com>,
	Bharata B Rao <bharata.rao@...il.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC][PATCH 00/26] sched/numa

On Mon, 2012-03-19 at 14:04 +0100, Andrea Arcangeli wrote:

> About the cost of the actual pagetable scanner, you're not being
> rational about it. You should measure it for once, take khugepaged
> make it scan 1G of memory per millisecond and measure the cost.

Death by a thousand cuts.. 

> You keep complaining about the unaccountability of the pagetable
> scanners in terms of process load, and that's a red herring as far as
> I can tell. The irqs and ksoftirqd load in a busy server, is likely
> much higher than whatever happens at the pagetable scanner level (sure
> thing for khugepaged and by an huge order of magnitude so). 

Who says I agree with ksoftirqd? I would love to get rid of all things
softirq. And I also think workqueues are over-/ab-used.

> I don't
> think this is a relevant concern anyway because the pagetable scanners
> go over all memory in a equal amount so the cost would be evenly
> distributed for all processes over time (the same cannot be said about
> the irqs and ksoftrqid that will benefit only a few processes doing
> I/O). 

So what about the case where all I do is compile kernels and we already
have near perfect locality because everything is short running? You're
still scanning that memory, and I get no benefit.
--
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/