On Sat, Jun 9, 2012 at 8:16 PM, <merez@xxxxxxxxxxxxxx> wrote: > >> Hi, >> >> How can we check the effect? >> Do you have any result? > We ran parallel lmdd read and write operations and found out that the > write packing causes the read throughput to drop from 24MB/s to 12MB/s. Whoa! That's a big drop. BTW, is there a problem with throughput or latency, or both ? If these numbers are over long duration (>5 seconds), then where are the cycles going? It would be nice to see some blktrace figures for the issue, and then fix it, rather than apply a band aid like the write-packing-control on top.. > The write packing control managed to increase the read throughput back to > the original value. > We also examined "real life" scenarios, such as performing a big push > operation in parallel to launching several applications. We measured the > read latency and found out that with the write packing control the worst > case of the read latency was smaller. > >> Please check the several comment below. >> >> Maya Erez <merez@xxxxxxxxxxxxxx> wrote: >>> The write packing control will ensure that read requests latency is >>> not increased due to long write packed commands. >>> >>> The trigger for enabling the write packing is managing to pack several >>> write requests. The number of potential packed requests that will >>> trigger >>> the packing can be configured via sysfs by writing the required value >>> to: >>> /sys/block/<block_dev_name>/num_wr_reqs_to_start_packing. >>> The trigger for disabling the write packing is fetching a read request. >>> -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
