> 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, Hi. What I first intended is not ufs_bsg but as you might already know, it also allocated its own request queue. In that point, we can imagine it could be the same situation. > 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? I used some benchmarks, such tiobench or Androbench that could make heavy IO scenarios. > - command upiu is not implemented, are all those IOs are query requests? What I've seen is just one query and many scsi commands. > > > 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 > >
