Date: Mon, 5 Nov 2012 02:41:58 +1100 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Kirk McKusick <mckusick@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r242520 - head/sys/ufs/ffs Message-ID: <20121105024038.J4726@besplex.bde.org> In-Reply-To: <201211031855.qA3Ituxr024809@svn.freebsd.org> References: <201211031855.qA3Ituxr024809@svn.freebsd.org>
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On Sat, 3 Nov 2012, Kirk McKusick wrote: > Log: > When a file is first being written, the dynamic block reallocation > (implemented by ffs_reallocblks_ufs[12]) relocates the file's blocks > so as to cluster them together into a contiguous set of blocks on > the disk. > > When the cluster crosses the boundary into the first indirect block, > the first indirect block is initially allocated in a position > immediately following the last direct block. Block reallocation > would usually destroy locality by moving the indirect block out of > the way to keep the data blocks contiguous. This change compensates > for this problem by noting that the first indirect block should be > left immediately following the last direct block. It then tries > to start a new cluster of contiguous blocks (referenced by the > indirect block) immediately following the indirect block. > > We should also do this for other indirect block boundaries, but it > is only important for the first one. > > Suggested by: Bruce Evans > MFC: 2 weeks Thanks. Sorry I haven't got around to testing your version of this. Bruce
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