Date: Wed, 26 Nov 1997 05:26:57 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, tlambert@primenet.com Cc: fs@FreeBSD.ORG Subject: Re: ufs slowness Message-ID: <199711251826.FAA15404@godzilla.zeta.org.au>
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>> After copying from ext2fs to ffs using two tars in a pipe, ffs is exactly >> as slow as before, although I've disturbed the ffs partition a little >> by building a world in it (it grew from 53% full to 66% full). > >How about copying back to ext2fs? Then at least the same algorithm >will have populated both. See later mail. It's slower, but I think that is because the FreeBSD ext2fs is worse that the Linux one :-). >I think "optimal" might be "in such a way that a file may not displace >a directory from cache". > >This would imply: > >1) Breadth first >2) Create all files before subdirectories for any directory > >Of course, I could be wrong. If it's depth first, with no way to >adjust it, you'd want the directories first. It's othing to do with that - see later mail. ffs wants to seek a lot to switch cylinder groups (for almost every new directory?), but I think the main problem is that it wants to seek lot to handle fragments. I'm now making space to repartition. I'll try a 4K/4K ffs to match the ext2fs block size exactly. Another thing: it didn't help to move all the files into one big directory (with ~2500 files and 38MB data). This was 20% slower, presumably due to the directory being too big to cache properly. Bruce
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