2009/7/15 Vladislav Bolkhovitin <vst@xxxxxxxx>: >> The drop with 64 max_sectors_kb on the client is a consequence of how CFQ >> is working. I can't find the exact code responsible for this, but from all >> signs, CFQ stops delaying requests if amount of outstanding requests exceeds >> some threshold, which is 2 or 3. With 64 max_sectors_kb and 5 SCST I/O >> threads this threshold is exceeded, so CFQ doesn't recover order of >> requests, hence the performance drop. With default 512 max_sectors_kb and >> 128K RA the server sees at max 2 requests at time. >> >> Ronald, can you perform the same tests with 1 and 2 SCST I/O threads, >> please? Ok. Should I still use the file-on-xfs testcase for this, or should I go back to using a regular block device? The file-over-iscsi is quite uncommon I suppose, most people will export a block device over iscsi, not a file. > With context-RA patch, please, in those and future tests, since it should > make RA for cooperative threads much better. > >> You can limit amount of SCST I/O threads by num_threads parameter of >> scst_vdisk module. Ok, I'll try that and include the blk_run_backing_dev, readahead-context and io_context patches. Ronald. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
