Re: Blocked processes <=> Elevator starvation?

From: Rui Sousa (rsousa@grad.physics.sunysb.edu)
Date: Sun Oct 08 2000 - 12:32:52 EST


On Sun, 8 Oct 2000, Rik van Riel wrote:

> On Sun, 8 Oct 2000, Rui Sousa wrote:
>
> > After starting 2 processes that scan a lot of files (diff, find,
> > slocate, ...) it's impossible to run any other processes that
> > touch the disk, they will stall until one of the first two stop.
> > Could this be a sign of starvation in the elevator code?
>
> It could well be. I've seen this problem too and don't
> really have another explanation for this phenomenon.
>
> OTOH, maybe there is another reason for it that hasn't
> been found yet ;)

I have looked into this a bit more. It seems you also need to be writing
to disk to cause processes to be blocked (otherwise they are just very
slow), for example redirecting the output of the above commands to a
file. I also did an strace of processes that I knew would be blocked and
and found two system calls that never return: stat() and mkdir()
Is this normal if the problem was the elevator code?

Rui Sousa

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