Messages in this thread | | | Date | Mon, 21 Feb 2011 13:55:38 +0800 | From | Gui Jianfeng <> | Subject | Re: [PATCH 3/6 v4] cfq-iosched: Introduce vdisktime and io weight for CFQ queue |
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Vivek Goyal wrote: > On Fri, Feb 18, 2011 at 02:04:18PM +0800, Gui Jianfeng wrote: >> Vivek Goyal wrote: >>> On Thu, Feb 10, 2011 at 03:47:16PM +0800, Gui Jianfeng wrote: >>> >>> [..] >>>> +/* >>>> + * The time when a CFQ queue is put onto a service tree is recoreded in >>>> + * cfqq->reposition_time. Currently, we check the first priority CFQ queues >>>> + * on each service tree, and select the workload type that contains the lowest >>>> + * reposition_time CFQ queue among them. >>>> + */ >>>> static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, >>>> struct cfq_group *cfqg, enum wl_prio_t prio) >>>> { >>>> struct cfq_entity *cfqe; >>>> + struct cfq_queue *cfqq; >>>> + unsigned long lowest_start_time; >>>> int i; >>>> - bool key_valid = false; >>>> - unsigned long lowest_key = 0; >>>> + bool time_valid = false; >>>> enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; >>>> >>>> + /* >>>> + * TODO: We may take io priority and io class into account when >>>> + * choosing a workload type. But for the time being just make use of >>>> + * reposition_time only. >>>> + */ >>>> for (i = 0; i <= SYNC_WORKLOAD; ++i) { >>>> - /* select the one with lowest rb_key */ >>>> cfqe = cfq_rb_first(service_tree_for(cfqg, prio, i)); >>>> - if (cfqe && >>>> - (!key_valid || time_before(cfqe->rb_key, lowest_key))) { >>>> - lowest_key = cfqe->rb_key; >>>> + cfqq = cfqq_of_entity(cfqe); >>>> + if (cfqe && (!time_valid || >>>> + time_before(cfqq->reposition_time, >>>> + lowest_start_time))) { >>>> + lowest_start_time = cfqq->reposition_time; >>> Gui, >>> >>> Have you had a chance to run some mixed workloads in a group (some sync, >>> some async and some sync-idle queues), and see how latency and throughput >>> of sync-idle workload changes due to this "resposition_time" logic. I >>> just want to make sure that latency of sync-noidle workload does not >>> go up as that's the workload that people care and gets noticed first. >> Hi Vivek, >> >> I made a quick test by using fio. It seems the number changes little >> between vanilla kernel and patched kernel. >> >> >> Vanilla: SYNC read SYNC-NOIDLE read ASYNC write >> 1. 23,640KB/s 5.40 ---- 6,696KB/s 19.07 ---- 50,142KB/s 128.00 >> 2. 24,459KB/s 5.22 ---- 6,775KB/s 18.86 ---- 47,349KB/s 129.89 >> 3. 25,929KB/s 4.93 ---- 7,378KB/s 17.32 ---- 32,350KB/s 131.88 >> >> Patched: SYNC read SYNC-NOIDLE read ASYNC write >> 1. 24,000KB/s 5.32 ---- 6,942KB/s 18.39 ---- 30,860KB/s 135.95 >> 2. 23,678KB/s 5.40 ---- 7,274KB/s 17.58 ---- 67,432KB/s 120.44 >> 3. 23,004KB/s 5.55 ---- 6,621KB/s 19.30 ---- 36,536KB/s 148.64 > > Hi Gui, > > Do you also have latency numbers? I am especially interested max completion > latencies of SYNC-NOIDLE workload.
Vivek,
Here some numbers about latency between vanilla and patched kernel. I tested 4 times for each. It seems no latency regression happens.
Vanilla: 1. clat (msec): min=1, max=302, avg=18.19, stdev=39.80 2. clat (msec): min=1, max=201, avg=17.76, stdev=31.90 3. clat (msec): min=1, max=303, avg=18.64, stdev=41.30 4. clat (msec): min=1, max=370, avg=17.43, stdev=35.09
Patched: 1. clat (msec): min=1, max=176, avg=19.00, stdev=32.98 2. clat (msec): min=1, max=175, avg=17.75, stdev=32.41 3. clat (msec): min=1, max=191, avg=19.11, stdev=33.28 4. clat (msec): min=1, max=176, avg=17.11, stdev=32.99
Thanks, Gui
> > Thanks > Vivek >
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