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From "Paul J. Reder" <rede...@remulak.net>
Subject Re: [PATCH] Possible fix for worker MPM performance problem (Updated patch)
Date Fri, 26 Apr 2002 15:32:19 GMT
Jeff,

In my tests, this patch allows existing worker threads to continue
procesing requests while the new threads are started.

In the previous code the server would pause while new threads were
being created. The new threads started accepting work immediately,
causing the existing threads to starve even though there are a
small (but growing) number of new threads.

This patch allows the server to maintain a higher level of responsiveness
during the ramp up time.

Paul J. Reder

Jeff Trawick wrote:

> "Bill Stoddard" <bill@wstoddard.com> writes:
> 
> (I would have quoted but the text is way out at columns 89-92 or so)
> 
> I think the patch is fine, but I can't help but suspect that some of
> the pain you are alleviating is caused by the known problem where the
> listener thread can accept connections when there are no spare workers
> to handle it.
> 
> Yes, the listener thread may do a little more at startup than a worker
> thread, but if it knew better than to go grab connections it couldn't
> service then would it really cause the system to thrash any more than
> it is going to thrash anyway in order to get those threads created and
> dispatched?
> 
> 
>>Index: worker.c
>>===================================================================
>>RCS file: /home/cvs/httpd-2.0/server/mpm/worker/worker.c,v
>>retrieving revision 1.117
>>diff -u -r1.117 worker.c
>>--- worker.c 18 Apr 2002 17:46:20 -0000 1.117
>>+++ worker.c 26 Apr 2002 14:50:43 -0000
>>@@ -948,6 +948,7 @@
>>     apr_status_t rv;
>>     int i;
>>     int threads_created = 0;
>>+    int listener_started = 0;
>>     int loops;
>>     int prev_threads_created;
>>
>>@@ -999,16 +1000,18 @@
>>                 clean_child_exit(APEXIT_CHILDFATAL);
>>             }
>>             threads_created++;
>>-            if (threads_created == 1) {
>>-                /* now that we have a worker thread, it makes sense to create
>>-                 * a listener thread (we don't want a listener without a worker!)
>>-                 */
>>-                create_listener_thread(ts);
>>-            }
>>+
>>+        }
>>+        /* Start the listener only when there are workers available */
>>+        if (!listener_started && threads_created) {
>>+            create_listener_thread(ts);
>>+            listener_started = 1;
>>         }
>>+
>>         if (start_thread_may_exit || threads_created == ap_threads_per_child) {
>>             break;
>>         }
>>+
>>         /* wait for previous generation to clean up an entry */
>>         apr_sleep(1 * APR_USEC_PER_SEC);
>>         ++loops;
>>
> 


-- 
Paul J. Reder
-----------------------------------------------------------
"The strength of the Constitution lies entirely in the determination of each
citizen to defend it.  Only if every single citizen feels duty bound to do
his share in this defense are the constitutional rights secure."
-- Albert Einstein



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