-----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-----