On Wed, Jan 16, 2008 at 01:30:43PM -0800, Valerie Henson wrote: > Hi y'all, > > This is a request for comments on the rewrite of the e2fsck IO > parallelization patches I sent out a few months ago. The mechanism is > totally different. Previously IO was parallelized by issuing IOs from > multiple threads; now a single thread issues fadvise(WILLNEED) and > then uses read() to complete the IO. Interesting. We ultimately rejected a similar patch to xfs_repair (pre-population the kernel block device cache) mainly because of low memory performance issues and it doesn't really enable you to do anything particularly smart with optimising I/O patterns for larger, high performance RAID arrays. The low memory problems were particularly bad; the readahead thrashing cause a slowdown of 2-3x compared to the baseline and often it was due to the repair process requiring all of memory to cache stuff it would need later. IIRC, multi-terabyte ext3 filesystems have similar memory usage problems to XFS, so there's a good chance that this patch will see the same sorts of issues. > Single disk performance doesn't change, but elapsed time drops by > about 50% on a big RAID-5 box. Passes 1 and 2 are parallelized. Pass > 5 is left as an exercise for the reader. Promising results, though.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
