linux-kernel - Re: [RFC patch] Use IPI_shortcut for lapic timer broadcast

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: <20090629070123.5e874497@infradead.org>
Date:	Mon, 29 Jun 2009 07:01:23 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Luming Yu <luming.yu@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	suresh.b.siddha@...el.com, venkatesh.pallipadi@...el.com,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC patch] Use IPI_shortcut for lapic timer broadcast

On Mon, 29 Jun 2009 16:43:16 +0800
Luming Yu <luming.yu@...il.com> wrote:

> > Even a Pentium-5 100 MHz dual box was able to do cross-CPU IPIs
> > within 10-20 microseconds more than a decade ago - so 50-100 usecs
> > latency on a modern platform is totally out of this planet and will
> > hurt Linux performance big time. And the worst thing about it is
> > that none of the usual performance metrics will really show _why_
> > performance is tanking ...
> >
> 
> 
> Please note this is deep-C-state related.
> C state does add extra latency.. but I don't know how much...

C states normally only add on the "wait for" side, not on the "send"
side.

(RHEL5 is rather old, so it may have done things a bit different)

Maybe it is time for mainline to not allow a !NO_HZ config....


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
--
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/