Sergio Lopez 5c06b7f862 vhost_user_block: Implement optional static polling ... Actively polling the virtqueue significantly reduces the latency of each I/O operation, at the expense of using more CPU time. This features is specially useful when using low-latency devices (SSD, NVMe) as the backend. This change implements static polling. When a request arrives after being idle, vhost_user_block will keep checking the virtqueue for new requests, until POLL_QUEUE_US (50us) has passed without finding one. POLL_QUEUE_US is defined to be 50us, based on the current latency of enterprise SSDs (< 30us) and the overhead of the emulation. This feature is enabled by default, and can be disabled by using the "poll_queue" parameter of "block-backend". This is a test using null_blk as a backend for the image, with the following parameters: - null_blk gb=20 nr_devices=1 irqmode=2 completion_nsec=0 no_sched=1 With "poll_queue=false": fio --ioengine=sync --bs=4k --rw randread --name randread --direct=1 --filename=/dev/vdb --time_based --runtime=10 randread: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=sync, iodepth=1 fio-3.14 Starting 1 process Jobs: 1 (f=1): [r(1)][100.0%][r=169MiB/s][r=43.2k IOPS][eta 00m:00s] randread: (groupid=0, jobs=1): err= 0: pid=433: Tue Feb 18 11:12:59 2020 read: IOPS=43.2k, BW=169MiB/s (177MB/s)(1688MiB/10001msec) clat (usec): min=17, max=836, avg=21.64, stdev= 3.81 lat (usec): min=17, max=836, avg=21.77, stdev= 3.81 clat percentiles (nsec): | 1.00th=[19328], 5.00th=[19840], 10.00th=[20352], 20.00th=[21120], | 30.00th=[21376], 40.00th=[21376], 50.00th=[21376], 60.00th=[21632], | 70.00th=[21632], 80.00th=[21888], 90.00th=[22144], 95.00th=[22912], | 99.00th=[28544], 99.50th=[30336], 99.90th=[39168], 99.95th=[42752], | 99.99th=[71168] bw ( KiB/s): min=168440, max=188496, per=100.00%, avg=172912.00, stdev=3975.63, samples=19 iops : min=42110, max=47124, avg=43228.00, stdev=993.91, samples=19 lat (usec) : 20=5.90%, 50=94.08%, 100=0.02%, 250=0.01%, 500=0.01% lat (usec) : 750=0.01%, 1000=0.01% cpu : usr=10.35%, sys=25.82%, ctx=432417, majf=0, minf=10 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued rwts: total=432220,0,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1 Run status group 0 (all jobs): READ: bw=169MiB/s (177MB/s), 169MiB/s-169MiB/s (177MB/s-177MB/s), io=1688MiB (1770MB), run=10001-10001msec Disk stats (read/write): vdb: ios=427867/0, merge=0/0, ticks=7346/0, in_queue=0, util=99.04% With "poll_queue=true" (default): fio --ioengine=sync --bs=4k --rw randread --name randread --direct=1 --filename=/dev/vdb --time_based --runtime=10 randread: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=sync, iodepth=1 fio-3.14 Starting 1 process Jobs: 1 (f=1): [r(1)][100.0%][r=260MiB/s][r=66.7k IOPS][eta 00m:00s] randread: (groupid=0, jobs=1): err= 0: pid=422: Tue Feb 18 11:14:47 2020 read: IOPS=68.5k, BW=267MiB/s (280MB/s)(2674MiB/10001msec) clat (usec): min=10, max=966, avg=13.60, stdev= 3.49 lat (usec): min=10, max=966, avg=13.70, stdev= 3.50 clat percentiles (nsec): | 1.00th=[11200], 5.00th=[11968], 10.00th=[11968], 20.00th=[12224], | 30.00th=[12992], 40.00th=[13504], 50.00th=[13760], 60.00th=[13888], | 70.00th=[14016], 80.00th=[14144], 90.00th=[14272], 95.00th=[14656], | 99.00th=[20352], 99.50th=[23936], 99.90th=[35072], 99.95th=[36096], | 99.99th=[47872] bw ( KiB/s): min=265456, max=296456, per=100.00%, avg=274229.05, stdev=13048.14, samples=19 iops : min=66364, max=74114, avg=68557.26, stdev=3262.03, samples=19 lat (usec) : 20=98.84%, 50=1.15%, 100=0.01%, 250=0.01%, 500=0.01% lat (usec) : 750=0.01%, 1000=0.01% cpu : usr=8.24%, sys=21.15%, ctx=684669, majf=0, minf=10 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued rwts: total=684611,0,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1 Run status group 0 (all jobs): READ: bw=267MiB/s (280MB/s), 267MiB/s-267MiB/s (280MB/s-280MB/s), io=2674MiB (2804MB), run=10001-10001msec Disk stats (read/write): vdb: ios=677855/0, merge=0/0, ticks=7026/0, in_queue=0, util=99.04% Signed-off-by: Sergio Lopez <slp@redhat.com>		2020-02-19 17:13:47 +00:00
..
bin	vhost_user_block: Implement optional static polling	2020-02-19 17:13:47 +00:00
main.rs	vhost_user_block: Implement optional static polling	2020-02-19 17:13:47 +00:00