linux-kernel - Re: [PATCH 0/2] convert mmap_sem to a scalable rw

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: <1179146281.6810.65.camel@twins>
Date:	Mon, 14 May 2007 14:38:01 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...sign.ru>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex

On Mon, 2007-05-14 at 13:58 +0200, Nick Piggin wrote:
> On Fri, May 11, 2007 at 05:56:21PM +0200, Ingo Molnar wrote:
> > 
> > * Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> > 
> > > I was toying with a scalable rw_mutex and found that it gives ~10% 
> > > reduction in system time on ebizzy runs (without the MADV_FREE patch).
> > > 
> > > 2-way x86_64 pentium D box:
> > > 
> > > 2.6.21
> > > 
> > > /usr/bin/time ./ebizzy -m -P
> > > 59.49user 137.74system 1:49.22elapsed 180%CPU (0avgtext+0avgdata 0maxresident)k
> > > 0inputs+0outputs (0major+33555877minor)pagefaults 0swaps
> > > 
> > > 2.6.21-rw_mutex
> > > 
> > > /usr/bin/time ./ebizzy -m -P
> > > 57.85user 124.30system 1:42.99elapsed 176%CPU (0avgtext+0avgdata 0maxresident)k
> > > 0inputs+0outputs (0major+33555877minor)pagefaults 0swaps
> > 
> > nice! This 6% runtime reduction on a 2-way box will i suspect get 
> > exponentially better on systems with more CPUs/cores.
> 
> Is this with the MADV_DONTNEED kernel and glibc work?

No, just the old stuff.

> 
> > i also like the design, alot: instead of doing a full new lock type 
> > (with per-arch changes, extra lockdep support, etc. etc) you layered the 
> > new abstraction ontop of mutexes. This makes this hard locking 
> > abstraction look really, really simple, while the percpu_counter trick 
> > makes it scale _perfectly_ for the reader case. Congratulations!
> > 
> > given how nice this looks already, have you considered completely 
> > replacing rwsems with this? I suspect you could test the correctness of 
> 
> Not to take anything away from this lock type (because it can have its
> uses), but have you considered the size of this lock and its write side
> performance? 

Yeah, I did, I was initially just toying about with the concept, to see
if it was doable at all. I only posted because I got these fairly good
numbers.

-
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/