[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Sat, 28 Feb 2015 10:42:48 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: semaphore redesign
On Sat, Feb 28, 2015 at 02:21:22AM +0300, Alexander Monakov wrote:
> Hello,
>
> As new cancellation has landed (except that __timedwait fails to propagate
> ECANCELED in addition to ETIMEDOUT and EINTR), I'm happy to post semaphore
> redesign. We discussed this implementation with Rich on IRC once, and
> presently I'm not aware of any issues (finally!), but still testing and
> performance comparison need to be done.
Thanks! I'm attaching a performance testing program I used in the
past. Its time measurement is not very precise, but it should show
large-scale differences. It measures the number of messages that can
be send back and forth between two threads in 2 seconds by cancelling
the two threads after sleep(2).
Some other things we should test for performance:
- Do something like the attached but with multiple threads contending
on semaphores rather than uncontended message passing.
- Time/cycles per call for sem_post and sem_trywait and uncontended
sem_wait -- this looks like it should be an obvious win though.
- Perhaps something to hammer posts and trywait -- it's not clear that
this would model any real-world behavior, but it could show
something interesting anyway.
I doubt we'll see any measurable differences in usage cases where the
futex syscall is expected; it should dominate there.
Rich
View attachment "sem_bench.c" of type "text/plain" (648 bytes)
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
