On Thu 10-12-20 10:44:33, Jan Kara wrote: > BFQ computes number of tags it allows to be allocated for each request type > based on tag bitmap. However it uses 1 << bitmap.shift as number of > available tags which is wrong. 'shift' is just an internal bitmap value > containing logarithm of how many bits bitmap uses in each bitmap word. > Thus number of tags allowed for some request types can be far to low. > Use proper bitmap.depth which has the number of tags instead. > > Signed-off-by: Jan Kara <jack@xxxxxxx> Ping Jens? I think it has fallen through the cracks? Honza > --- > block/bfq-iosched.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c > index 9e81d1052091..9e4eb0fc1c16 100644 > --- a/block/bfq-iosched.c > +++ b/block/bfq-iosched.c > @@ -6332,13 +6332,13 @@ static unsigned int bfq_update_depths(struct bfq_data *bfqd, > * limit 'something'. > */ > /* no more than 50% of tags for async I/O */ > - bfqd->word_depths[0][0] = max((1U << bt->sb.shift) >> 1, 1U); > + bfqd->word_depths[0][0] = max(bt->sb.depth >> 1, 1U); > /* > * no more than 75% of tags for sync writes (25% extra tags > * w.r.t. async I/O, to prevent async I/O from starving sync > * writes) > */ > - bfqd->word_depths[0][1] = max(((1U << bt->sb.shift) * 3) >> 2, 1U); > + bfqd->word_depths[0][1] = max((bt->sb.depth * 3) >> 2, 1U); > > /* > * In-word depths in case some bfq_queue is being weight- > @@ -6348,9 +6348,9 @@ static unsigned int bfq_update_depths(struct bfq_data *bfqd, > * shortage. > */ > /* no more than ~18% of tags for async I/O */ > - bfqd->word_depths[1][0] = max(((1U << bt->sb.shift) * 3) >> 4, 1U); > + bfqd->word_depths[1][0] = max((bt->sb.depth * 3) >> 4, 1U); > /* no more than ~37% of tags for sync writes (~20% extra tags) */ > - bfqd->word_depths[1][1] = max(((1U << bt->sb.shift) * 6) >> 4, 1U); > + bfqd->word_depths[1][1] = max((bt->sb.depth * 6) >> 4, 1U); > > for (i = 0; i < 2; i++) > for (j = 0; j < 2; j++) > -- > 2.16.4 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
