Re: [patch] run_task_queue(&tq_disk) overhead in __wait_on_xxx

Stephen C. Tweedie (sct@redhat.com)
Fri, 30 Apr 1999 01:59:02 +0100 (BST)


Hi,

On Wed, 28 Apr 1999 22:31:54 +0200 (CEST), Andrea Arcangeli
<andrea@e-mind.com> said:

> I think the implementation of wait_on_page() and wait_on_buffer() are not
> too much friendly with the I/O subsystem. The problem is that such two
> functions does a run_task_queue() even if after the wakeup the page was
> just unlocked. So they are probably going to do I/O too early even if not
> needed.

The important cases of deferred disk IO are all places where we spin
with the kernel lock building up a list of buffers for IO. In such
cases, nobody can interrupt us and preempt the run_task_queue(), so I
can't see it making much of a difference in real use.

--Stephen

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