Christoph Hellwig <hch@xxxxxxxxxxxxx> writes: > On Tue, Jun 22, 2010 at 05:34:59PM -0400, Jeff Moyer wrote: >> Hi, >> >> Running iozone with the fsync flag, or fs_mark, the performance of CFQ is >> far worse than that of deadline for enterprise class storage when dealing >> with file sizes of 8MB or less. I used the following command line as a >> representative test case: >> >> fs_mark -S 1 -D 10000 -N 100000 -d /mnt/test/fs_mark -s 65536 -t 1 -w 4096 -F >> >> When run using the deadline I/O scheduler, an average of the first 5 numbers >> will give you 448.4 files / second. CFQ will yield only 106.7. With >> this patch series applied (and the two patches I sent yesterday), CFQ now >> achieves 462.5 files / second. >> >> This patch set is still an RFC. I'd like to make it perform better when >> there is a competing sequential reader present. For now, I've addressed >> the concerns voiced about the previous posting. > > What happened to the initial idea of just using the BIO_RW_META flag > for log writes? In the end log writes are the most important writes you > have in a journaled filesystem, and they should not be effect to any > kind of queue idling logic or other interruption. Log I/O is usually > very little (unless you use old XFS code with a worst-case directory > manipulation workload), and very latency sensitive. Vivek showed that starting firefox in the presence of a processing doing fsyncs (using the RQ_META approach) took twice as long as without the patch: http://lkml.org/lkml/2010/4/6/276 Cheers, Jeff -- 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
