On 05/22/18 19:46, Jens Axboe wrote: > On 5/22/18 10:20 AM, Jens Axboe wrote: >> On 5/22/18 10:17 AM, Holger Hoffstätte wrote: >>> On 05/22/18 16:48, Jianchao Wang wrote: >>>> Currently, kyber is very unfriendly with merging. kyber depends >>>> on ctx rq_list to do merging, however, most of time, it will not >>>> leave any requests in ctx rq_list. This is because even if tokens >>>> of one domain is used up, kyber will try to dispatch requests >>>> from other domain and flush the rq_list there. >>>> >>>> To improve this, we setup kyber_ctx_queue (kcq) which is similar >>>> with ctx, but it has rq_lists for different domain and build same >>>> mapping between kcq and khd as the ctx & hctx. Then we could merge, >>>> insert and dispatch for different domains separately. If one domain >>>> token is used up, the requests could be left in the rq_list of >>>> that domain and maybe merged with following io. >>>> >>>> Following is my test result on machine with 8 cores and NVMe card >>>> INTEL SSDPEKKR128G7 >>>> >>>> fio size=256m ioengine=libaio iodepth=64 direct=1 numjobs=8 >>>> seq/random >>>> +------+---------------------------------------------------------------+ >>>> |patch?| bw(MB/s) | iops | slat(usec) | clat(usec) | merge | >>>> +----------------------------------------------------------------------+ >>>> | w/o | 606/612 | 151k/153k | 6.89/7.03 | 3349.21/3305.40 | 0/0 | >>>> +----------------------------------------------------------------------+ >>>> | w/ | 1083/616 | 277k/154k | 4.93/6.95 | 1830.62/3279.95 | 223k/3k | >>>> +----------------------------------------------------------------------+ >>>> When set numjobs to 16, the bw and iops could reach 1662MB/s and 425k >>>> on my platform. >>>> >>>> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx> >>> >>> <snip> >>> >>> This looks great but prevents kyber from being built as module, >>> which is AFAIK supposed to work (and works now): >>> >>> .. >>> CC [M] block/kyber-iosched.o >>> Building modules, stage 2. >>> MODPOST 313 modules >>> ERROR: "bio_attempt_back_merge" [block/kyber-iosched.ko] undefined! >>> ERROR: "bio_attempt_front_merge" [block/kyber-iosched.ko] undefined! >>> ERROR: "bio_attempt_discard_merge" [block/kyber-iosched.ko] undefined! >>> ERROR: "blk_try_merge" [block/kyber-iosched.ko] undefined! >>> ERROR: "blk_rq_merge_ok" [block/kyber-iosched.ko] undefined! >>> .. >>> >>> It does build fine when compiled in, obviously. :) >> >> It's basically duplicating the contents of blk_attempt_plug_merge(). >> I would suggest abstracting out the list loop and merge check >> into a helper, that could then both be called from kyber and the >> plug merge function. > > See attached, prep patch and yours rebased on top of it. That was quick. :) Applies smoothly on top of my 4.16++ tree, now builds correctly as module and is reproducibly (slightly) faster even on my pedestrian SATA SSDs, now on par or occasionally even faster than mq-deadline. What's not to like? So: Tested-by: Holger Hoffstätte <holger@xxxxxxxxxxxxxxxxxxxxxx> cheers, Holger
