Hi, > Hi, > > ufs_bsg was introduced nearly three years ago and it allocates its own request > queue. > I faced a sytmpom with this and want to ask something about it. > > That is, sometimes queue depth for ufs is limited to half of the its maximum > value > even in a situation with many IO requests from filesystem. This is interesting indeed. Before going further with investigating this, Could you share some more details on your setup: The bsg node it creates was originally meant to convey a single query request via SG_IO ioctl, Which is blocking. - How do you create many IO requests queueing on that request queue? - command upiu is not implemented, are all those IOs are query requests? Thanks, Avri > It turned out that it only occurs when a query is being processed at the same > time. > Regarding my tracing, when the query process starts, users for the hctx that > represents > a ufs host increase to two and with this, some pathes calling 'hctx_may_queue' > function in blk-mq seems to throttle dispatches, technically with 16 because the > number of > ufs slots (32 in my case) is dividend by two (users). > > I found that it happened when a query for write booster is processed > because write booster only turns on in some conditions in my base that is > different > from kernel mainline. But when an exceptional event or others that could lead > to a query occurs, > it can happen even in mainline. > > I think the throttling is a little bit excessive, > so the question: is there any way to assign queue depth per user on an > asymmetric basis? > > Thanks. > Kiwoong Kim >
