From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Mahoney Subject: Re: ReiserFS v3 choking when free space falls below 10%? Date: Fri, 07 Jul 2006 14:08:05 -0400 Message-ID: <44AEA305.9050509@suse.com> References: <1152059846.30139.11.camel@ipso.snappymail.ca> <44AB25EE.8030702@namesys.com> <20060706125856.fdac1d16.pegasus@nerv.eu.org> <1152200638.30139.45.camel@ipso.snappymail.ca> <44AD5020.6050803@suse.com> <1152210439.30139.59.camel@ipso.snappymail.ca> <44AD58D1.9040806@suse.com> <1152257397.13211.43.camel@ipso.snappymail.ca> <20060707174935.GB13606@atrey.karlin.mff.cuni.cz> <44AE9EFB.7060301@suse.com> <20060707180746.GA29487@atrey.karlin.mff.cuni.cz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <20060707180746.GA29487@atrey.karlin.mff.cuni.cz> List-Id: Content-Type: text/plain; charset="us-ascii" To: Jan Kara Cc: Mike Benoit , =?UTF-8?B?SnVyZSBQZcSNYXI=?= , Hans Reiser , reiserfs-list@namesys.com -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Jan Kara wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> Jan Kara wrote: >>> Hi, >>> >>> just one note: I've looked to the in scan_bitmap() in bitmap.c. There is: >>> /* When the bitmap is more than 10% free, anyone can allocate. >>> * When it's less than 10% free, only files that already use the >>> * bitmap are allowed. Once we pass 80% full, this restriction >>> * is lifted. >>> * >>> * We do this so that files that grow later still have space >>> * close to >>> * their original allocation. This improves locality, and >>> * presumably >>> * performance as a result. >>> * >>> * This is only an allocation policy and does not make up for >>> * getting a >>> * bad hint. Decent hinting must be implemented for this to work >>> * well. >>> */ >>> if (TEST_OPTION(skip_busy, s) >>> && SB_FREE_BLOCKS(s) > SB_BLOCK_COUNT(s) / 20) { >>> >>> So the comment suggests we should lift the restriction when we are 80% >>> full but if you see the condition, it checks wherher we are 95% full! I >>> guess that is really asking for trouble and could explain the >>> behaviour... >>> Mike could you try changing that 20 in the test to 5? IMHO that could >>> fix your problem. >> Shoot. I guess I never sent that mail out last night. I had discovered >> the same thing. The thing is, I don't think it will cause the kind of >> performance problem we're seeing here. Once it sees the 90% check it >> will bail out. Minor slowdown, not anything like we're seeing. > Hmm, right. You'll only scan that one bitmap the file is in, won't > you? That can still take some time so maybe it's worth trying this fix > anyway. Oh, I agree that it's a bug that needs to be fixed. I just don't think it's causing 90% CPU usage. :) - -Jeff - -- Jeff Mahoney SUSE Labs -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iD8DBQFErqMELPWxlyuTD7IRAnitAJ9rbkY8sKzJqqVZnwA1Gqo2aEcV1QCgqBgt YsXQ7d6S/70du/bWQ28Xhkc= =Jv9h -----END PGP SIGNATURE-----