Date: Thu, 23 Oct 2003 11:08:02 -0700 From: Ken Marx <kmarx@vicor.com> To: Julian Elischer <julian@vicor.com> Cc: mckusick@beastie.mckusick.com Subject: Re: 4.8 ffs_dirpref problem Message-ID: <3F981902.90607@vicor.com> In-Reply-To: <20031023171932.9F36C7A425@mail.vicor-nb.com> References: <20031023171932.9F36C7A425@mail.vicor-nb.com>
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Thanks for the reply, We actually *did* try -s 4096 yesterday (not quite what you suggested) with spotty results: Sometimes it seemed to go more quickly, but often not. Let me clarify our test: We have a 1.5gb tar file from our production raid that fairly represents the distribution of data. We hit the performance problem when we get to dirs with lots of small-ish files. But, as Julian mentioned, we typically have many flavors of file sizes and populations. Admittedly, our untar'ing test isn't necessarily representitive of what happens in production - we were just trying to fill the disk and recreate the problem here. We *did* at least hit a noticeable problem, and we believe it's the same behavior that's hitting production. I just tried your exact suggested settings on an fs that was already 96% full, and still experienced the very sluggish behavior on exactly the same type of files/dirs. Our untar typically takes around 60-100 sec of system time when things are going ok; 300-1000+ sec when the sluggishness occurs. This time tends to increase as we get closer to 99%. Sometimes as high as 4000+ secs. I wasn't clear from your mail if I should newfs the entire fs and start over, or if I could have expected the settings to make a difference for any NEW data. I can do this latter if you think it's required. The test will then take several hours to run since we need at least 85% disk usage to start seeing the problem. Thanks! k Julian Elischer wrote: >>From mckusick@beastie.mckusick.com Wed Oct 22 22:30:03 2003 >>X-Original-To: julian@vicor-nb.com >>Delivered-To: julian@vicor-nb.com >>To: Ken Marx <kmarx@vicor.com> >>Subject: Re: 4.8 ffs_dirpref problem >>Cc: freebsd-fs@freebsd.org, cburrell@vicor.com, davep@vicor.com, >> jpl@vicor.com, jrh@vicor.com, julian@vicor-nb.com, VicPE@aol.com, >> julian@vicor.com, Grigoriy Orlov <gluk@ptci.ru> >>In-Reply-To: Your message of "Wed, 22 Oct 2003 12:57:53 PDT." >> <20031022195753.27C707A49F@mail.vicor-nb.com> >>Date: Wed, 22 Oct 2003 16:37:54 -0700 >>From: Kirk McKusick <mckusick@beastie.mckusick.com> > > >>I believe that you can dsolve your problem by tuning the existing >>algorithm using tunefs. There are two parameters to control dirpref, >>avgfilesize (which defaults to 16384) and filesperdir (which defaults >>to 50). I suggest that you try using an avgfilesize of 4096 and >>filesperdir of 1500. This is done by running tunefs on the unmounted >>(or at least mounted read-only) filesystem as: > > >> tunefs -f 4096 -s 1500 /dev/<disk for my broken filesystem> > > > On the same filesystem are directories that contain 1GB files > and others that contain maybe 100 100K files (images) > > > >>Note that this affects future layout, so needs to be done before you >>put any data into the filesystem. If you are building the filesystem >>from scratch, you can use: > > > would this have an effect on an existing filesystem with respect to new data > being added to it? > > > > > >> newfs -g 4096 -h 1500 ... >> >>to set these fields. Please let me know if this solves your problem. >>If it does not, I will ask Grigoriy Orlov <gluk@ptci.ru> if he has >>any ideas on how to proceed. > > >> Kirk McKusick > > >>=-=-=-=-=-=-= > > > -- Ken Marx, kmarx@vicor-nb.com It's too costly to get lean and mean and analyze progress on the diminishing expectations. - http://www.bigshed.com/cgi-bin/speak.cgi
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