On Fri, Jun 28 2013, Jan Kara wrote: > In case a device has three tags available we still reserve two of them > for sync IO. That leaves only a single tag for async IO such as > writeback from flusher thread which results in poor performance. > > Allow async IO to consume two tags in case queue has three tag availabe > to get a decent async write performance. > > This patch improves streaming write performance on a machine with such disk > from ~21 MB/s to ~52 MB/s. Also postmark throughput in presence of > streaming writer improves from 8 to 12 transactions per second so sync > IO doesn't seem to be harmed in presence of heavy async writer.
That's pretty crazy! Never seen a device like that. But yes, it obviously exists, and the 2 reserved tags doesn't work well for that. So it's an improvement. Thanks, will queue up for 3.11. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
