From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 05 Jul 2005 08:31:40 -0700 From: "Martin J. Bligh" Reply-To: "Martin J. Bligh" Subject: Re: [rfc] lockless pagecache Message-ID: <54750000.1120577500@[10.10.2.4]> In-Reply-To: <20050705151119.GA12279@kevlar.burdell.org> References: <200506271942.j5RJgig23410@unix-os.sc.intel.com> <20050705151119.GA12279@kevlar.burdell.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Sonny Rao , "Chen, Kenneth W" Cc: 'Christoph Lameter' , 'Badari Pulavarty' , 'Nick Piggin' , Lincoln Dale , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: >> > On Mon, 27 Jun 2005, Chen, Kenneth W wrote: >> > > I don't recall seeing tree_lock to be a problem for DSS workload either. >> > >> > I have seen the tree_lock being a problem a number of times with large >> > scale NUMA type workloads. >> >> I totally agree! My earlier posts are strictly referring to industry >> standard db workloads (OLTP, DSS). I'm not saying it's not a problem >> for everyone :-) Obviously you just outlined a few .... > > I'm a bit late to the party here (was gone on vacation), but I do have > profiles from DSS workloads using page-cache rather than O_DIRECT and > I do see spin_lock_irq() in the profiles which I'm pretty certain are > locks spinning for access to the radix_tree. I'll talk about it a bit > more up in Ottawa but here's the top 5 on my profile (sorry don't have > the number of ticks at the momement): > > 1. dedicated_idle (waiting for I/O) > 2. __copy_tofrom_user > 3. radix_tree_delete > 4. _spin_lock_irq > 5. __find_get_block > > So, yes, if the page-cache is used in a DSS workload then one will see > the tree-lock. BTW, this was on a PPC64 machine w/ a fairly small > NUMA factor. The easiest way to confirm the spin-lock thing is to recompile with CONFIG_SPINLINE, and take a new profile, then diff the two ... M. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org