From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Sun, 28 Mar 2004 19:23:57 +0000 Subject: Re: should ia64_spinlock_contention do backoff? Message-Id: <20040328192357.GC26179@parcelfarce.linux.theplanet.co.uk> List-Id: References: <200403251941.i2PJfrTH026392@napali.hpl.hp.com> In-Reply-To: <200403251941.i2PJfrTH026392@napali.hpl.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Fri, Mar 26, 2004 at 04:14:13PM -0800, Chen, Kenneth W wrote: > This question is a bit too broad, lock contention highly depends on workload. Surely. > For example, I'm doing direct I/O on bunch of block devices, and the dev nodes > sit on reiserfs, this contention shows up: > > 79.7% 91.2% 18us(1415us) 449us( 760ms)(57.9%) 2970234 8.8% 91.2% 0% kernel_flag > 0.00% 92.3% 5.8us( 35us) 689us( 58ms)(0.01%) 298 7.7% 92.3% 0% __break_lease+0x80 I'm not familiar with this output; I'm assuming this means __break_lease() is a major contributor to the amount that kernel_flag (ie the BKL) is locked? That's interesting; I assume you're using Samba as part of your workload since it's the only major user of leases that I'm aware of. Hmm.. seems to me we should move time_out_leases() down 5 lines to minimise the amount of time we spend with the BKL held if there's a non-lease lock held on the file. I wish we'd managed to get the file locking code BKL-free during 2.5 but it just didn't happen ;-( -- "Next the statesmen will invent cheap lies, putting the blame upon the nation that is attacked, and every man will be glad of those conscience-soothing falsities, and will diligently study them, and refuse to examine any refutations of them; and thus he will by and by convince himself that the war is just, and will thank God for the better sleep he enjoys after this process of grotesque self-deception." -- Mark Twain