Hello Dan Burkert, Todd Lipcon,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/9021
to look at the new patch set (#2).
Change subject: KUDU-1913: LIFO wake up ordering for threadpool worker threads
......................................................................
KUDU-1913: LIFO wake up ordering for threadpool worker threads
This patch changes the wake-up ordering for idle pool worker threads
to be LIFO. Previously all worker threads idled on a single
ConditionVariable which, by virtue of using pthread_cond_t under the hood,
was FIFO ordered.
In the abstract, FIFO ordering ensures a fair distribution of work amongst a
set of threads, but that's totally undesirable in a thread pool where the
goal is to get work done as quickly and with as few threads as possible. For
example, a fast stream of cheap tasks (e.g. RPCs) should be serviceable via
a single thread or something close to that.
The new unit test was looped 1000 times in TSAN mode with 8 stress threads
to shake out any flakes. Additionally, I ran through a variation of Todd's
test from a past code review [1]. I spun up three tservers, two of which had
failure detection disabled so that the third would get all of the leader
replicas. I created 240 tablets and looked at the size of the Raft thread
pool on that tserver. The steady state thread count was mildly lower at
first (4 vs. 8) but was much lower (4 vs. 30) after a SIGSTOP+SIGCONT cycle.
1. https://gerrit.cloudera.org/c/7331
Change-Id: I8036bf0d15f9ffcb3fa76579e3bfe0a340d38320
---
M src/kudu/util/test_util.cc
M src/kudu/util/test_util.h
M src/kudu/util/threadpool-test.cc
M src/kudu/util/threadpool.cc
M src/kudu/util/threadpool.h
5 files changed, 114 insertions(+), 15 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/21/9021/2
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I8036bf0d15f9ffcb3fa76579e3bfe0a340d38320
Gerrit-Change-Number: 9021
Gerrit-PatchSet: 2
Gerrit-Owner: Adar Dembo <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Dan Burkert <[email protected]>
Gerrit-Reviewer: Todd Lipcon <[email protected]>
