> time I prefer to intoroduce tunables only on need basis otherwise it
> runs the risk of too many tunables which are not being used.
>
> So, conceptually this patch looks fine to me. Jeff Moyer also raised the
> same question of why not fill up the quantum if READ/WRITE are not using
> their quota. So I think it does not hurt to take this patch in.
>
> Acked-by: Vivek Goyal <vgoyal@redhat.com>
>
> Thanks
> Vivek
>
>>
>> Thanks
>> Hillf
>>
>> >
>> > Generally READS are more latency sensitive as compared to WRITE hence
>> > I thought of dispatching more READS per quantum.
>> >
>> > Thanks
>> > Vivek
>> >
>> >>
>> >> --- a/block/blk-throttle.c 2010-11-01 19:54:12.000000000 +0800
>> >> +++ b/block/blk-throttle.c 2010-11-26 21:49:00.000000000 +0800
>> >> @@ -647,11 +647,16 @@ static int throtl_dispatch_tg(struct thr
>> >> unsigned int max_nr_reads = throtl_grp_quantum*3/4;
>> >> unsigned int max_nr_writes = throtl_grp_quantum - nr_reads;
>> >> struct bio *bio;
>> >> + int read_throttled = 0, write_throttled = 0;
>> >>
>> >> /* Try to dispatch 75% READS and 25% WRITES */
>> >> -
>> >> + try_read:
>> >> while ((bio = bio_list_peek(&tg->bio_lists[READ]))
>> >> - && tg_may_dispatch(td, tg, bio, NULL)) {
>> >> + && ! read_throttled) {
>> >> + if (! tg_may_dispatch(td, tg, bio, NULL)) {
>> >> + read_throttled = 1;
>> >> + break;
>> >> + }
>> >>
>> >> tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
>> >> nr_reads++;
>> >> @@ -659,9 +664,15 @@ static int throtl_dispatch_tg(struct thr
>> >> if (nr_reads >= max_nr_reads)
>> >> break;
>> >> }
>> >> -
>> >> + if (! bio)
>> >> + read_throttled = 1;
>> >> + try_write:
>> >> while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
>> >> - && tg_may_dispatch(td, tg, bio, NULL)) {
>> >> + && ! write_throttled) {
>> >> + if (! tg_may_dispatch(td, tg, bio, NULL)) {
>> >> + write_throttled = 1;
>> >> + break;
>> >> + }
>> >>
>> >> tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
>> >> nr_writes++;
>> >> @@ -669,7 +680,23 @@ static int throtl_dispatch_tg(struct thr
>> >> if (nr_writes >= max_nr_writes)
>> >> break;
>> >> }
>> >> + if (! bio)
>> >> + write_throttled = 1;
>> >> +
>> >> + if (write_throttled && read_throttled)
>> >> + goto out;
>> >>
>> >> + if (! (throtl_grp_quantum > nr_writes + nr_reads))
>> >> + goto out;
>> >> +
>> >> + if (read_throttled) {
>> >> + max_nr_writes = throtl_grp_quantum - nr_reads;
>> >> + goto try_write;
>> >> + } else {
>> >> + max_nr_reads = throtl_grp_quantum - nr_writes;
>> >> + goto try_read;
>> >> + }
>> >> + out:
>> >> return nr_reads + nr_writes;
>> >> }
>> >> --
>> >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> >> the body of a message to
majordomo@vger.kernel.org
>> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> >> Please read the FAQ at http://www.tux.org/lkml/
>> >
>
