linux-kernel - Re: [rfc] scale dcache locking

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] [day] [month] [year] [list]

Message-ID: <20090402094305.GE22256@wotan.suse.de>
Date:	Thu, 2 Apr 2009 11:43:05 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [rfc] scale dcache locking

On Wed, Apr 01, 2009 at 03:23:12PM +0100, Al Viro wrote:
> On Mon, Mar 30, 2009 at 02:55:39AM +1100, npiggin@...e.de wrote:
> > This is my sketch for improving dcache locking scalability. So far I've
> > only really been looking at core code to get an idea of how it might look,
> > so most configurable functionality is broken (and unfortunately it might
> > well be something in there which will cause a fundamental problem for me).
> 
> Umm...  Some of that makes obvious sense per se, some...  In particular,
> all of a sudden we get contention between multiple dput() on the same
> dentry, which is dirt-common for directory ones.

Yes that's true but I'm hoping lock hold times on d_lock aren't
too long, in which case the major cost should remain just the
cacheline contention.

Hmm, I wanted to avoid the atomic because it tends to be covered
by d_lock a lot of the time anyway so avoiding the extra locked op,
and also makes concurrency a bit easier to think about.

In worst case, I guess we need to reintroduce atomic refcount or
have another lock for it...

--
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/