Slow response times for some + ICMP from Moodle?

Slow response times for some + ICMP from Moodle?

by Phil Hopfner -
Number of replies: 1

Hello all,

I have a performance issue that I am still trying to track down.  We have a relatively beefy server (PowerEedge 2950 of recent vintage) with lotsa RAM, CPU, etc running Moodle 1.9.2 on a LAMP stack with Fedora 9 as the OS.

I've tried to follow the PHP and MySQL tuning tips scattered throughout the forum and also on the Moodle docs site.  However, some clients (and myself on occasion) have poor response times on the WAN side. NOt all the time...but sometimes.  Long timeouts displaying forum pages, or sometimes even the Front Page.

I've been monitoring via sar and collectl and the server seems to be idling most of the time (low CPU and disk activity, network and RAM = low usage) - yet the problem persists.  I've been capturing packets now trying to analyze the conversations and on thing I noticed was that every so often, Moodle throws out ICMP packets.  These are blocked at our routers and I see the ICMP packets around the same time that the timeouts are occurring.

Why is Moodle initiating ICMP packets?  I'm probably just not familiar enough with the TCP/IP stack..but no one is "pinging " from the server at the time they occur.  That...and any other tips to isolate these slow (60+ second) timeouts would be appreciated.

Thanks all.

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In reply to Phil Hopfner

Re: Slow response times for some + ICMP from Moodle?

by Phil Hopfner -

Just to followup on my own posting....

The problem is a little better now and the main change that seemed to have an affect was to increase the HTTP KeepAlive Timeout from a value of 3 to a value 60.  This seems counter-intuitive to the Moodle Performance docs, so I thought I'd just post it.   Once we made that tweak, the ICMP messages being generated from the server dropped dramatically.  There are still slow responses being reported by the students - but not as many.

One thing different about our site is that the whole thing runs in HTTPS.  We use mod-rewrite to force all Moodle work to be done in HTTPS (this was a requirement so that the students could exchange info securely).

I still welcome any thoughts.  Thanks.

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