Todd Lipcon has submitted this change and it was merged. (
http://gerrit.cloudera.org:8080/15440 )
Change subject: rpc: reduce context switches and receive calls
......................................................................
rpc: reduce context switches and receive calls
* When queueing a task to execute on the reactor, avoid writing to the
eventfd to wake it up if such a write has already been done. This
should reduce the number of read/write syscalls to the eventfd and
avoid "spurious" wakeups of the reactor.
* When reading inbound data, read an extra 4 bytes, and if it's
available, loop around to read another call without putting the
reactor back to sleep.
The effect on context switches is clearly visible using
rpc-bench --gtest_filter=\*Async
Before:
I0305 12:50:56.463312 7468 rpc-bench.cc:128] Ctx Sw. per req: 0.640409
I0305 12:50:58.015260 7542 rpc-bench.cc:128] Ctx Sw. per req: 0.613172
I0305 12:50:59.563201 7587 rpc-bench.cc:128] Ctx Sw. per req: 0.589479
I0305 12:51:01.014848 7662 rpc-bench.cc:128] Ctx Sw. per req: 0.562744
I0305 12:51:02.666339 7736 rpc-bench.cc:128] Ctx Sw. per req: 0.569126
After:
I0305 12:52:03.567790 9005 rpc-bench.cc:128] Ctx Sw. per req: 0.383251
I0305 12:52:05.050909 9079 rpc-bench.cc:128] Ctx Sw. per req: 0.454404
I0305 12:52:06.626401 9138 rpc-bench.cc:128] Ctx Sw. per req: 0.3308
I0305 12:52:08.123154 9198 rpc-bench.cc:128] Ctx Sw. per req: 0.317752
I0305 12:52:09.666586 9272 rpc-bench.cc:128] Ctx Sw. per req: 0.391739
And on system CPU:
Before:
I0305 12:50:56.463310 7468 rpc-bench.cc:127] Sys CPU per req: 16.5524us
I0305 12:50:58.015259 7542 rpc-bench.cc:127] Sys CPU per req: 16.1158us
I0305 12:50:59.563199 7587 rpc-bench.cc:127] Sys CPU per req: 17.3184us
I0305 12:51:01.014847 7662 rpc-bench.cc:127] Sys CPU per req: 16.7911us
I0305 12:51:02.666337 7736 rpc-bench.cc:127] Sys CPU per req: 15.7659us
After:
I0305 12:52:03.567787 9005 rpc-bench.cc:127] Sys CPU per req: 13.0533us
I0305 12:52:05.050906 9079 rpc-bench.cc:127] Sys CPU per req: 13.7925us
I0305 12:52:06.626399 9138 rpc-bench.cc:127] Sys CPU per req: 11.6987us
I0305 12:52:08.123152 9198 rpc-bench.cc:127] Sys CPU per req: 11.9214us
I0305 12:52:09.666584 9272 rpc-bench.cc:127] Sys CPU per req: 13.4031us
And on syscalls:
todd@turbo:~/kudu$ grep recvfr /tmp/before /tmp/after
/tmp/before: 1458969 syscalls:sys_enter_recvfrom
( +- 1.99% )
/tmp/before: 1458969 syscalls:sys_exit_recvfrom
( +- 1.99% )
/tmp/after: 1252328 syscalls:sys_enter_recvfrom
( +- 1.82% )
/tmp/after: 1252328 syscalls:sys_exit_recvfrom
( +- 1.82% )
todd@turbo:~/kudu$ grep epoll_ctl /tmp/before /tmp/after
/tmp/before: 915862 syscalls:sys_enter_epoll_ctl
( +- 1.47% )
/tmp/before: 915862 syscalls:sys_exit_epoll_ctl
( +- 1.47% )
/tmp/after: 475978 syscalls:sys_enter_epoll_ctl
( +- 3.61% )
/tmp/after: 475978 syscalls:sys_exit_epoll_ctl
( +- 3.61% )
On a more macro-benchmark (TSBS single-groupby-1-1-1 16 workers on an
8-core machine) this also reduces syscalls a bit, though the end-to-end
improvement is minimal.
Before:
Performance counter stats for 'system wide' (10 runs):
340,444 cs
( +- 0.30% )
144,024 syscalls:sys_enter_recvfrom
( +- 0.00% )
94,379 syscalls:sys_enter_epoll_ctl
( +- 0.06% )
129,376 syscalls:sys_enter_epoll_wait
( +- 0.10% )
2.025755946 seconds time elapsed
( +- 0.43% )
After:
Performance counter stats for 'system wide' (10 runs):
333,865 cs
( +- 0.27% )
119,216 syscalls:sys_enter_recvfrom
( +- 0.04% )
88,731 syscalls:sys_enter_epoll_ctl
( +- 0.08% )
104,149 syscalls:sys_enter_epoll_wait
( +- 0.08% )
2.005614271 seconds time elapsed
( +- 0.19% )
Change-Id: I32c5e4d146c25be8e90665a0cb8385fcd017b15c
Reviewed-on: http://gerrit.cloudera.org:8080/15440
Reviewed-by: Andrew Wong <[email protected]>
Tested-by: Andrew Wong <[email protected]>
Reviewed-by: Bankim Bhavsar <[email protected]>
---
M src/kudu/rpc/connection.cc
M src/kudu/rpc/reactor.cc
M src/kudu/rpc/transfer.cc
M src/kudu/rpc/transfer.h
4 files changed, 71 insertions(+), 37 deletions(-)
Approvals:
Andrew Wong: Looks good to me, approved; Verified
Bankim Bhavsar: Looks good to me, but someone else must approve
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: I32c5e4d146c25be8e90665a0cb8385fcd017b15c
Gerrit-Change-Number: 15440
Gerrit-PatchSet: 3
Gerrit-Owner: Todd Lipcon <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Bankim Bhavsar <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Todd Lipcon <[email protected]>
