What the 'low_latency' knob does

Posted Oct 8, 2009 12:44 UTC (Thu) by Yenya (subscriber, #52846)
In reply to: What the 'low_latency' knob does by axboe
Parent article: The CFQ "low latency" mode

Do you think the low-latency knob could help also for situations like ordinary filesystem traffic versus background md-RAID resync?

I had a pretty bad experience with CFQ on my FTP server (ftp.linux.cz, SW RAID-5 over 8x 1TB SATA drives) - the resync of the array with CFQ took about 3 days with the overall system responsiveness being pretty bad, while with the deadline iosched (which is what I am running now) it takes less than a day, and even then the system latency for things like typing commands to a ssh session is good (read: no noticeable change against the fully reconstructed array).

-Yenya