Date: Sat, 04 Sep 2004 00:59:42 -0700 From: Julian Elischer <julian@elischer.org> To: Don Lewis <truckman@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: what is fsck's "slowdown"? Message-ID: <413975EE.4030400@elischer.org> In-Reply-To: <200409040709.i8479U79031043@gw.catspoiler.org> References: <200409040709.i8479U79031043@gw.catspoiler.org>
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Don Lewis wrote: > On 3 Sep, Matthew Dillon wrote: > >> There may be some tricks you can use to improve your fsck times on that >> large partition. >> >> The first thing you can try is to compile up an fsck with a much larger >> in-program disk buffer cache. cd into /usr/src/sbin/fsck and edit >> fsck_ffs/fsck.h. Significantly increase MAXBUFSPACE and INOBUFSIZE. >> e.g. try increasing MAXBUFSPACE from 40MB to 200MB, and INOBUFSIZE from >> 56MB to 200MB. >> >> Another possibility would be to try to improve disk I/O linearity by >> modifying getdatablk() in fsutil.c to read-ahead several blocks rather >> then just one. This would require some programming. >> >> The remaining tricks involve reformatting the large partition to >> increase the block size and/or increase the number of bytes/inode >> (thus reducing the number of inodes). The larger the block size, the >> easier it is for fsck to track down indirect blocks. The fewer inodes >> the partition has, the less work fsck has to do. But, of course, to do >> this you have to backup all the data on the partition, newfs it with >> the new parameters, and restore all the data back. Maximizing the >> number of cylinders/group also helps a great deal but I think newfs >> already does that by default. > > > This sort of thing was my initial thought, but the posted CPU usage > statistics show that fsck is burning up most of its CPU cycles in > userland. > > >>>load: 0.99 cmd: fsck 67 [running] 15192.26u 142.30s 99% 184284k > > > Increasing MAXBUFSPACE looks like it would make the problem worse > because getdatablk() does a linear search. > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" if you are using an alternate superblock then teh hash routines devolve into a single linked list.. make si treally sloww..
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