Date: Mon, 6 Dec 1999 14:13:38 -0800 (PST) From: Julian Elischer <julian@whistle.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Zhihui Zhang <zzhang@cs.binghamton.edu>, "Ronald G. Minnich" <rminnich@lanl.gov>, freebsd-fs@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG Subject: Re: ELF & putting inode at the front of a file Message-ID: <Pine.BSF.4.10.9912061410540.20503-100000@current1.whistle.com> In-Reply-To: <199912062133.NAA72851@apollo.backplane.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, 6 Dec 1999, Matthew Dillon wrote: > :On Mon, 6 Dec 1999, Ronald G. Minnich wrote: > : > :> On Mon, 6 Dec 1999, Zhihui Zhang wrote: > :> > I have modified FFS filesystem code to put the disk inode at the beginning > :> > of a file, i.e, the logical block #0 of each file begins with 128 bytes of > :> > its disk inode and the rest of it are file data. > :> > :> first question I have is, why? > : > :I am doing some research on filesystem. I guess it may be faster to put > :the disk inode with its file data together so that both can be read into > :memory in one I/O. > : > :-Zhihui > > Not really. The inode tends to wind up being cached by the system > longer then file data, so placing it with the file data will not > help -- since it is already probably cached, the system generally doesn't > have to read it off the disk more then once anyway, and in a heavily > loaded system the system caching is sufficiently detached from the file > data processing that it is actually more beneficial to group inodes > together (one disk read is able to cache many inodes all in one go). > > Another problem is that things like 'ls -la' or 'find' have to stat files > and if you put the inode at the beginning of the file you essentially > distribute the inodes all over the cylinder group rather then concentrate > all the inodes in one place. > > p.s. I was wrong about it breaking mmap() - in fact offseting the file > data on-disk will not break mmap(). But it will produce unaligned disk > transfers and potentially extra seeking. At Usenix 98 there was a paper on puting the inode in ht edirectory entry for files with only one link. that DID speed a lot of things up.. Puting the inode in "frag -1" is interesting, but the question remains of how do you find the inode? I presume the directory entry needs to have the actual disk block in it.. > > -Matt > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-fs" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSF.4.10.9912061410540.20503-100000>