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SubjectRe: [patch(?)] question wrt context switching during disk i/o

On Sat, 21 Oct 2000, Bill Wendling wrote:

> } > bdflush is broken in current kernels. I posted to linux-mm about this,
> } > but Rik et al haven't shown any interest. I normally see bursts of
> } > up to around 40K cs/second when doing writes; I hacked a little
> } > premption counter into the kernel and verified that they're practially
> } > all bdflush...
> }
> There's some strangness in bdflush(). The comment says:
>
> /*
> * If there are still a lot of dirty buffers around,
> * skip the sleep and flush some more. Otherwise, we
> * go to sleep waiting a wakeup.
> */
> if (!flushed || balance_dirty_state(NODEV) < 0) {
> run_task_queue(&tq_disk);
> schedule();
> }

Speaking of bdflush brokenness, I was trying to tune it using
/proc/sys/vm/bdflush. I was trying to eliminate the bursty write behaviour
Linux always seems to have had (exhibited by e.g. find /).

Unfortunately, different /proc/sys/vm/bdflush settings didn't seem to have
much (if any) effect. Is this another case of /proc/sys/vm/* settings
being ignored? If so they should be removed.

I was hoping to get a steady trickle of writes instead of the occasional
mammoth burst.

Cheers
Chris

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