Re: Better choice for Linux semaphore than spinlock?

Folks:

I spoke with this user late last week. They stated that they can only get
approximately 400 parallel SVN operations before the "system time" consumes
all available CPU for an 8-core machine. Adding more cores won't help
because of the nature of spin locks (it makes things worse). Turns out
that even with ~100 parallel SVN operations the "system time" starts
becoming significant/measurable (~10%). Both HTTP (mod_dav_svn) and
"svnserve" protocols participate in the lock contention.

Your help would be greatly appreciated.

Cheers.

Doug

On Fri, Oct 4, 2019 at 9:20 AM Doug Robinson <doug.robinson_at_wandisco.com>
wrote:

> Folks:
>
> From a Subversion user:
>
> “... we have very high concurrent connections to Subversion that seem to
> crater Subversion. The SVN Serve process we use to access the Subversion
> repository is using the “svn” protocol by our “system user”, mostly
> read-only. Then, we, on behalf of the user make request to Subversion
> using the “http” protocol to fetch their data. So we have lots of
> connections to Subversion. But the volume of concurrent requests over the
> “svn” protocol cause the “svnserve” process to consume CPU cycles in a
> kernel “mutex-lock” which is implemented using “spin locks”. The “svnserve”
> process makes the mutex calls using the “apache” (APR) semaphore wait
> calls, but on Linux this is a “mutext-lock” request.”
>
> So is there a better, more scalable, semaphore that can be used?
>
> Cheers.
>
> Doug
> --
> *DOUGLAS B ROBINSON* SENIOR PRODUCT MANAGER
>
> T +1 925 396 1125
> *E* doug.robinson_at_wandisco.com
>

-- 
*DOUGLAS B ROBINSON* SENIOR PRODUCT MANAGER
T +1 925 396 1125
*E* doug.robinson_at_wandisco.com
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