Messages in this thread | | | Subject | Re: Poor desktop responsiveness with background I/O-operations | From | Mike Galbraith <> | Date | Mon, 21 Sep 2009 06:23:54 +0200 |
| |
On Sun, 2009-09-20 at 17:22 -0700, Justin P. Mattock wrote: > Wow, at first I did not notice anything > from your *.sh script, but then a few moments > later, the system became vary sluggish. firefox > takes about 15 seconds to load. OS is mint linux > with the latest HEAD on an imac9,1.
CFQ inherits IO priority from the parent on fork(), so nicing a shell or the dd should (and does) help a LOT. It also inherits the CPU scheduler class. I just checked, and IO does indeed inherit SCHED_IDLE as well as the RT classes (SCHED_BATCH does nothing). Setting the dd to SCHED_IDLE makes a big difference, as it should, so there's a bigger hammer than nice + ionice. SCHED_IDLE is CPU_adorable + IO_nicest.
Anyway, the problem seems to have to have at least two facets: 1. streaming IO causing pagecache reclaim. That problem doesn't seem to want to go away. Fixing that won't help 2 one bit though.
2. reads are sync, more heavily affected by seek latency than writes. If the disk your binaries live on is seeking a lot, you pay a LOT.
Hohum, IO + VM = haaaaard ;-)
-Mike
| |