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    SubjectRe: [PATCH 2.6.9-rc2 1/2] enhanced I/O accounting data collection
    Hi,

    > Index: linux/drivers/block/ll_rw_blk.c
    > ===================================================================
    > --- linux.orig/drivers/block/ll_rw_blk.c 2004-09-12 22:31:31.000000000 -0700
    > +++ linux/drivers/block/ll_rw_blk.c 2004-09-27 12:37:04.374234677 -0700
    > @@ -1741,6 +1741,7 @@
    > {
    > DEFINE_WAIT(wait);
    > struct request *rq;
    >+ unsigned long start_wait = jiffies;
    >
    > generic_unplug_device(q);
    > do {
    >@@ -1769,6 +1770,7 @@
    > finish_wait(&rl->wait[rw], &wait);
    > } while (!rq);
    >
    >+ current->bwtime += (unsigned long) jiffies - start_wait;
    > return rq;
    > }

    What is the purpose of this hunk alone as block io accounting? It
    doesn't make any sense to me - you are accounting the time a process
    spends sleeping on a congested queue, it has nothing to do with the
    bandwidth time it used. Which, btw, isn't so easy to account on queueing
    hardware.

    Just curious on what you are trying to achieve here.

    --
    Jens Axboe

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