linux-kernel - Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex

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: <1405989175.25048.5.camel@buesod1.americas.hpqcorp.net>
Date:	Mon, 21 Jul 2014 17:32:55 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Darren Hart <dvhart@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>,
	Waiman Long <Waiman.Long@...com>,
	Ingo Molnar <mingo@...nel.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Jason Low <jason.low2@...com>,
	Scott J Norton <scott.norton@...com>
Subject: Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex

On Mon, 2014-07-21 at 14:31 -0700, Andy Lutomirski wrote:
> On Mon, Jul 21, 2014 at 2:27 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > All this is predicated on the fact that syscalls are 'expensive'.
> > Weren't syscalls only 100s of cycles? All this bitmap mucking is far
> > more expensive due to cacheline misses, which due to the size of the
> > things is almost guaranteed.
> 
> 120 - 300 cycles for me, unless tracing happens, and I'm working on
> reducing the incidence of tracing.

fwiw here's what lmbench's lat_ctx says on my system . For 'accuracy', I
kept the runs short.

http://www.stgolabs.net/lat_ctx.png

--
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/