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https://issues.apache.org/jira/browse/TS-2137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13746054#comment-13746054
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ASF subversion and git services commented on TS-2137:
-----------------------------------------------------

Commit 10abd558ab8b209bcb8ecab4ae85e4c8af9c1fd9 in branch refs/heads/master 
from [~yunkai]
[ https://git-wip-us.apache.org/repos/asf?p=trafficserver.git;h=10abd55 ]

Add TS-2137/TS-2141 info to CHANGES file

                
> Use eventfd instread of pthread signal/wait in ATS
> --------------------------------------------------
>
>                 Key: TS-2137
>                 URL: https://issues.apache.org/jira/browse/TS-2137
>             Project: Traffic Server
>          Issue Type: Improvement
>          Components: Core, Logging, Stats
>            Reporter: Yunkai Zhang
>            Assignee: Yunkai Zhang
>             Fix For: 3.5.0
>
>         Attachments: 
> 0001-TS-2137-Use-eventfd-instread-of-pthread-signal-wait-.patch, 
> 0001-TS-2137-Use-eventfd-instread-of-pthread-signal-wait-.V2.patch, 
> 0001-TS-2137-Use-eventfd-instread-of-pthread-signal-wait-.V3.patch, 
> 0001-TS-2137-Use-eventfd-instread-of-pthread-signal-wait-.V4.patch, 
> eventfd_vs_pthread_cond_benchmark.tar.gz
>
>
> pthread_cond_signal/wait is used in several places in ATS, including but not 
> limited:
> 1) Logging system.
> 2) ProtectedQueue in event system.
> 3) RecProcess in stats system.
> As we known, pthread_cond_signal() need to take lock, it'll cause more 
> context switch than eventfd.
> I have wrote a simple benchmark program to compare the speed of eventfd and 
> pthread_cond notify mechanism.
> You can get the benchmark program from attachment: 
> https://issues.apache.org/jira/secure/attachment/12598570/eventfd_vs_pthread_cond_benchmark.tar.gz,
>  and test it by yourself if interesting.
> What the program do is that:
> 1) Create 10 producer threads and 1 consumer thread.
> 2) Producer threads will notify consumer concurrently in a loop.
> 3) The consumer thread will receive notification up to a given loop times.
> Here is my testing result, the command line argument is loop times(1000000) 
> of consumer:
> {code}
> [eventfd_vs_pthread_cond_benchmark]$ ls
> main.cc  Makefile
> [eventfd_vs_pthread_cond_benchmark]$ make
> g++ -g -o eventfd_test main.cc -DHAVE_EVENTFD -lpthread
> g++ -g -o pthread_cond_test main.cc -lpthread
> [eventfd_vs_pthread_cond_benchmark]$ ls
> eventfd_test  main.cc  Makefile  pthread_cond_test
> [eventfd_vs_pthread_cond_benchmark]$ time ./eventfd_test 1000000
> real    0m11.644s
> user    0m1.517s
> sys     1m31.179s
> [eventfd_vs_pthread_cond_benchmark]$ time ./pthread_cond_test 1000000
> real    0m57.438s
> user    0m30.152s
> sys     6m7.289s
> {code}
> We can see that eventfd is about 5 times faster than pthread_cond notify 
> mechanism.

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