Problem in brief: I am unable to increase HTTP/SSL connection rate,
while my Apache server platform shows a huge (98%) CPU slack.
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I benchmark the performance of several Linux/Open Source applications on
Intel Architecture (IA32/x86) servers. In this context, I am trying to
measure the peak HTTP connection rate sustained when SSL is enabled in
Apache. A 'connection' in this benchmark consists of:
TCP Connect
HTTP Connect
GET_SSL(a small file with a few bytes)
HTTP Disconnect
TCP Disconnect
My test server side test setup consists of:
(1) Intel 5300 Xeon (quad core) 2.67GHz, dual socket platform (with
Intel 5000P chipset) - i.e., an 8 way SMP platform
(2) Linux 2.6.13 (CentOS 4.1)
(3) Apache 2.0.52
(4) OpenSSL 0.9.7e
(5) Intel 82571 PCI Express Gigabit Ethernet NIC
My client side test set up consists of:
IxIA L4-L7 network traffic generator that is capable of generating upto
***-220 connections/sec-*** and emulate several thousand simultaneous
HTTP/SSL clients. (Aptixia XM12 test chassis with IxIA Application Logic
Module test card).
The IxIA test module, when tested against Windows 2000/IIS has measured
up to ***-220 HTTPS connections per second-*** on a 2.8GHz single
CPU/single core Xeon platform.
PROBLEM: When I test my Linux/Apache server for the same HTTPS
connection rate, my IxIA tester measures ***-at most 10
connections/sec-***, while my server shows at least a 98% CPU slack (as
measured using Linux TOP utility). I have played with various TCP
connection/persistence/buffer options, but with no improvement what so
ever.
Also, when I run the same test without SSL, I get a huge connection rate
of ***-40000 HTTP connections/sec-***. This leads me to believe that the
problem lies somewhere with the modSSL module & not Apache itself,
...but I am totally clueless after probing OpenSSL stack for several
weeks. Some basic Ethereal analysis shows that the server is issuing a
TCP RESET for nearly almost all connection requests from the IxIA
(virtual) clients.
NOTE: The client side test configuration & load is identical for both
Windows 2000/IIS and Linux/Apache.
I would greatly appreciate any known insights into this issue.
- Hari
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Hari Tadepalli
Sr Staff Performance Engineer
Intel Corporation
Infrastructure Processor Division
Chandler, AZ 85226
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