Re: Time sliced CFQ io scheduler

Andrew Morton
2004-12-02T19:44:22Z

Jens Axboe <axboe@suse.de> wrote:
>
> 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?

Looks like it. We used to do 2/3rds-read, 1/3rd-write in that testcase.