From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: [GIT PULL] adaptive spinning mutexes Date: Fri, 16 Jan 2009 13:37:10 -0500 Message-ID: <4970D3D6.3040906@tmr.com> References: <1231863710.7141.3.camel@twins> <1231864854.7141.8.camel@twins> <1231867314.7141.16.camel@twins> <1231952436.14825.28.camel@laptop> <20090114183319.GA18630@elte.hu> <20090114184746.GA21334@elte.hu> <20090114192811.GA19691@elte.hu> <20090115174440.GF29283@parisc-linux.org> <20090115180844.GL22472@elte.hu> <1232047618.8269.93.camel@think.oraclecorp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1232047618.8269.93.camel@think.oraclecorp.com> Cc: linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Chris Mason wrote: > On Thu, 2009-01-15 at 10:16 -0800, Linus Torvalds wrote: >> On Thu, 15 Jan 2009, Ingo Molnar wrote: >>> btw., i think spin-mutexes have a design advantage here: in a lot of code >>> areas it's quite difficult to use spinlocks - cannot allocate memory, >>> cannot call any code that can sporadically block (but does not _normally_ >>> block), etc. >>> >>> With mutexes those atomicity constraints go away - and the performance >>> profile should now be quite close to that of spinlocks as well. >> Umm. Except if you wrote the code nicely and used spinlocks, you wouldn't >> hold the lock over all those unnecessary and complex operations. >> > > While this is true, there are examples of places we should expect > speedups for this today. > > Concurrent file creation/deletion in a single dir will often find things > hot in cache and not have to block anywhere (mail spools). > And although not as common, NNTP servers using file per article storage. > Concurrent O_DIRECT aio writes to the same file, where i_mutex is > dropped early on. > > pipes should see a huge improvement. > I'd like to see that. Didn't realize how slow pipes really are. > I'll kick off some runs of my three benchmarks on ext3 for comparison. > If there are things less synthetic people would like to see, please let > me know. > > -chris > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot