linux-kernel - Re: [PATCH 1/3] lglock: remove online variants of lock

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: <87txzrb3qi.fsf@rustcorp.com.au>
Date:	Tue, 08 May 2012 15:42:37 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Nick Piggin <npiggin@...nel.dk>, Andi Kleen <ak@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/3] lglock: remove online variants of lock

On Tue, 8 May 2012 05:50:44 +0100, Al Viro <viro@...IV.linux.org.uk> wrote:
> On Tue, May 08, 2012 at 01:29:45PM +0930, Rusty Russell wrote:
> > Optimizing the slow paths adds a lot of complexity.  If you need to
> > grab every lock often, you have other problems.
> 
> Applied, but I'm not too happy about the situation with vfsmount_lock ;-/
> On kernels built for a lot of possible CPUs the loss of ..._online()
> versions will get painful.

My original motivation was to get rid of that cpumask_t (and replace it
with a cpumask_var_t).  A simple enough patch, but I couldn't bring
myself to leave that complex logic in place without clear justification.

> OTOH, we can always put the map + single
> spinlock + single notifier into lglock.c and reproduce the old logics.
> I'll do a patch along those lines and put it on a separate branch;
> then we'll be able to test and compare.

I'll be interested in the results: virtual systems are classic for
wanting large # of CPUs which aren't actually online, so we might
actually care.

I'd also like to get rid of the cpu_possible_map altogether, and just
have NR_CPUS/nr_cpu_ids, since last I checked no arch really wants
sparse numbers.

Cheers,
Rusty.
--
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/