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Re: (Round 3) Proposed patch to support: draft-zeilenga-ldap-c-api-concurrency

Doug Leavitt wrote:
   Since my last patch submission (Round2) I spent a considerable
amount of time performing performance analysis of my proposed
both client side and server side.

Sounds good, I've done a very brief review. I'd like to see the LWP removal as a separate patch. Also would like to see the introduction of LDAP_MUTEX_LOCK() and friends as a separate patch, before the real functionality changes.

The client side testing primarily consisted of running parallel
copies of slapd-mtread and monitoring in real time with dtrace
to monitor the behavior of all the concurrent threads in clients
looking for signs of thread starvation.  I was not able to find any.

On the server side I performed similar testing while using modified
versions of the test036-meta-concurrency and test020-proxycache
test cases.  Again looking for thread starvation.

Additionally, on the server side I setup single server and proxy cache
server environments, in combination with slamd to perform head to
head comparisons of
      HEAD (most recently as of 10/7/10)
      HEAD (most recently as of 10/7/10) and the round 3 MT patches

to see if there was any performance degradations or other
performance issues, especially related to situations where slapd
was using libldap_r as part of various backends.

The results of the head to head comparisons, especially in the
proxycache situation, show a 3% performance improvement with
the MT patches over the HEAD without the patches.

The reason according to dtrace outputs is that there are now cases,
especially in ldap_result where my proposed patch has up to 50% less calls
to thread_lock/unlock than are performed in the current HEAD.

All of the head to head dslam/dtrace results are included along with
the other patch materials.

The proposed patch details are located here:


Details about the contents of
is located here:


  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/