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. -- Jens Axboe
