Re: [PATCH] O11int for interactivity

Martin Josefsson
2003-08-05T17:05:56Z

On Tue, 2003-08-05 at 07:55, Andrew Morton wrote:

> Another possibility is that xmms is getting stuck in a read. The
> anticipatory scheduler is currently rather tuned for throughput. Judging
> by the vmstat trace which was posted, we have a classic
> read-stream-vs-write-stream going on. We trade off latency versus
> throughput; perhaps wrongly. You can decrease latency (at the expense of
> throughput) by decreasing the settings in /sys/block/hda/queue/iosched.
>
> To a point, it is a nice linear tradeoff, and someone should put the time
> in to tweak and characterise it.

I believe it was my trace wli posted.
No swapping was going on, swappiness set to 30

X was quite jerky and uninteractive during this and sometimes it froze
for up to 5 seconds (the sound usually stopped during the freezing).

Since there wasn't any swapping going on and quite a lot of cpu left we
either have quite some latency when reading back parts of X that
previously got discarded or massive stalls in kernelspace somewhere.

One thing I noticed was that when evolution started checking for new
mail in a lot of folders I get a lot of seeks and the throughput
naturally decreased but X got really responsive again. This points away
from X beeing discarded and read back in from disk since that would take
some time with all those seeks as well.

The machine this was tested on is a pIII 700 with 704MB ram and IDE
disks (everything was against the same disk)

--
/Martin