Re: Time sliced CFQ io scheduler

Jens Axboe
2004-12-02T13:48:31Z

Hi,

One more test case, while the box is booted... This just demonstrates a
process doing a file write (bs=64k) with a competing process doing a
file read (bs=64k) at the same time, again capped at 30sec.

deadline:
Reader: 2520KiB/sec (max_lat=45msec)
Writer: 1258KiB/sec (max_lat=85msec)

as:
Reader: 27985KiB/sec (max_lat=34msec)
Writer: 64KiB/sec (max_lat=1042msec)

cfq:
Reader: 12703KiB/sec (max_lat=108msec)
Writer: 9743KiB/sec (max_lat=89msec)

If you look at vmstat while running these tests, cfq and deadline give
equal bandwidth for the reader and writer all the time, while as
basically doesn't give anything to the writer (a single block per second
only). Nick, is the write batching broken or something?

--
Jens Axboe