[blk-lib] 6a0608544e5: fileio -77.4% max latency, -5.7% throughput

Fengguang Wu
2014-03-04T13:21:36Z

Hi Kent,

FYI, we noticed the below changes on

git://evilpiepirate.org/~kent/linux-bcache.git for-jens
commit 6a0608544e5672bd9a044c285119547eae41abe5 ("blk-lib.c: generic_make_request() handles large bios now")

test case: snb-drag/sysbench/fileio/600s-100%-1HDD-ext4-64G-1024-seqrewr-sync

11541d5f5b7002b 6a0608544e5672bd9a044c285
--------------- -------------------------
1885 ~60% -77.4% 426 ~ 7% TOTAL fileio.request_latency_max_ms
6258 ~ 0% -5.7% 5904 ~ 0% TOTAL fileio.requests_per_sec
26 ~ 1% +702.3% 211 ~ 8% TOTAL slabinfo.kmalloc-4096.num_slabs
217 ~ 1% +682.3% 1697 ~ 8% TOTAL slabinfo.kmalloc-4096.num_objs
26 ~ 1% +702.3% 211 ~ 8% TOTAL slabinfo.kmalloc-4096.active_slabs
211 ~ 2% +701.5% 1697 ~ 8% TOTAL slabinfo.kmalloc-4096.active_objs
2 ~ 0% -50.0% 1 ~ 0% TOTAL vmstat.procs.b
2236 ~ 0% +63.6% 3659 ~ 3% TOTAL slabinfo.kmalloc-256.num_objs
2217 ~ 0% +63.4% 3623 ~ 3% TOTAL slabinfo.kmalloc-256.active_objs
3274 ~ 1% +47.8% 4837 ~ 2% TOTAL proc-vmstat.nr_slab_unreclaimable
13096 ~ 1% +47.7% 19350 ~ 2% TOTAL meminfo.SUnreclaim
62558204 ~ 5% -30.7% 43379766 ~ 1% TOTAL cpuidle.C3-SNB.time
91031 ~ 4% -29.4% 64253 ~ 2% TOTAL cpuidle.C1E-SNB.usage
34092 ~ 2% -17.6% 28085 ~ 1% TOTAL cpuidle.C3-SNB.usage
2656 ~ 2% -15.0% 2258 ~ 2% TOTAL proc-vmstat.kswapd_high_wmark_hit_quickly
266339 ~ 2% +14.2% 304129 ~ 0% TOTAL cpuidle.C6-SNB.usage
21899 ~ 2% +9.6% 23992 ~ 2% TOTAL interrupts.RES
20 ~ 0% -8.0% 18 ~ 2% TOTAL time.percent_of_cpu_this_job_got
3430189 ~ 0% -5.9% 3226430 ~ 0% TOTAL time.voluntary_context_switches
117 ~ 0% -6.0% 110 ~ 0% TOTAL time.system_time
11691 ~ 0% -5.6% 11042 ~ 0% TOTAL vmstat.system.cs
711 ~ 0% +4.4% 742 ~ 0% TOTAL iostat.sda.await
712 ~ 0% +4.4% 743 ~ 0% TOTAL iostat.sda.w_await
99142 ~ 0% -2.2% 96963 ~ 0% TOTAL iostat.sda.wkB/s
99257 ~ 0% -2.2% 97110 ~ 0% TOTAL vmstat.io.bo
139 ~ 0% +1.7% 141 ~ 0% TOTAL iostat.sda.avgqu-sz

fileio.requests_per_sec

6300 ++----------------------------------------------------------*-------+
6250 *+.*.. .*.*..*..*..*..*..*.*..*..*..*..*..*.*..*..*..*..*. *..*..*
| *. |
6200 ++ |
6150 ++ |
| |
6100 ++ |
6050 ++ |
6000 ++ O |
| O O |
5950 O+ O O |
5900 ++ O O O O O |
| O O O O O O |
5850 ++ O O O |
5800 ++------------------------------------------------------------------+

fileio.request_latency_max_ms

4500 ++------------------------------------------------------------------+
| * |
4000 ++ : |
3500 ++ :: |
| : : |
3000 ++ * : : |
2500 ++ *.. + : * : : |
| + + : + : : : |
2000 ++ .*.. + * : + : : : |
1500 ++ * *.. *.. .* * : .*..*..*..*..: : .*
*.. .. .. .* *. : *. |
1000 ++ .* * *. * |
500 ++ *. O |
O O O O O O O O O O O O O O O O O O O |
0 ++------------------------------------------------------------------+

Thanks,
Fengguang