[PATCH] Cache messaging dgm connections

[Andrew Bartlett]

On Sun, 2016-09-11 at 20:33 +0200, Ralph Böhme wrote:
> On Sun, Sep 11, 2016 at 10:51:20AM -0700, Jeremy Allison wrote:
> > 
> > On Sun, Sep 11, 2016 at 04:07:15PM +0200, Ralph Böhme wrote:
> > > 
> > > Hi!
> > > 
> > > Attached is a performance improvement for our dgram messaging.
> > > 
> > > In most cases, the current code opens a new connection to peers
> > > for
> > > every message and closes it when done. This patchset adds caching
> > > of
> > > connections to peers.
> > > 
> > > Please review & push if ok.
> > 
> > OK, I have to ask :-) - I'm guessing you've already tested
> > this and have a good idea of how much performance improvement you
> > get under load...
> > 
> > Care to share the numbers ?
> 
> copying the Linux kernel sources with robocopy (with /MT:16) from a
> Windows client to the server, in a perf profile
> messaging_send_iov_from() showed up with taken 3%. Only 0.5% was for
> the sendmsg(), the rest is (un)become_root() (2.2%) and
> socket+connect.

And the overall performance?

I ask because Douglas did a very similar analysis of some 'obvious'
performance patches I did:

https://www.samba.org/~dbagnall/perf-tests/ldb.html

Likewise, when I added a cache of LDB index values between
transactions, it was obvious that it would help, because an index read
would be avoided, except when Douglas and I checked the performance, we
found the cache management costs took up the same space.  Eventually I
realised the primary cost, and got:

https://git.samba.org/?p=samba.git;a=commitdiff;h=f6e87188b60bea7d15bc015a8617e7ed3f7fbeda 
and
https://git.samba.org/?p=samba.git;a=commitdiff;h=e517d68a8f2772b863a7c072bd95d224b4ab8bf4

Andrew Bartlett

-- 
Andrew Bartlett                       http://samba.org/~abartlet/
Authentication Developer, Samba Team  http://samba.org
Samba Developer, Catalyst IT          http://catalyst.net.nz/services/samba