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From "Lu, Yingqi" <yingqi...@intel.com>
Subject RE: FW: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support
Date Tue, 04 Mar 2014 18:42:55 GMT
Hi Jeff,

Thanks very much for your time reviewing the patch! We will modify the patch according to
your comments and repost it here.

Thanks,
Yingqi

From: Jeff Trawick [mailto:trawick@gmail.com]
Sent: Tuesday, March 04, 2014 10:08 AM
To: Apache HTTP Server Development List
Subject: Re: FW: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support

On Tue, Mar 4, 2014 at 10:35 AM, Lu, Yingqi <yingqi.lu@intel.com<mailto:yingqi.lu@intel.com>>
wrote:
Hi All,

I just want to ping again on this patch to gather your feedback and comments. Please refer
to the messages below for patch details.

If you need any additional information/supporting data, please let us know as well.

Yeah, it has been on my todo list, but I don't have time to give an in depth review at the
moment.  Here are a few questions/comments.  (And you'll have to deal with the fact that it
is unnecessarily tedious for me to evaluate higher-level considerations if there are a lot
of distractions, such as the code comments below ;)  But others are of course free to chime
in.)

The patch should be against httpd trunk.  It probably won't take much time for you to create
that patch and confirm basic operation.

What is the impact to other MPMs, even if they shouldn't use or don't have the necessary code
to use SO_REUSEPORT at this time?

Have you tried the event MPM?

Is there a way for the admin to choose this behavior?  Most won't care, but everyone's behavior
is changed AFAICT.

Are there built-in limitations in this patch that we should be aware of?  E.g., the free slot/spawn
rate changes suggest to me that there can't be more than 1025 children???

We should assume for now that there's no reason this couldn't be committed to trunk after
review/rework, so make sure it is as close as you can get it to what you think is the final
form.

For the configure-time check for 3.9 kernel: I think we'd also use AC_TRY_COMPILE at configure
time to confirm that the SO_REUSEPORT definition is available, and not enable it if the system
includes doesn't define it.  (Does that cause a problem for any significant number of people?)

Don't mention the patch in the patch ;) (e.g., "This function is added for the patch.")

Incomplete comments on style/syntax issues:

* mixing declarations and statements (e.g., "duplr->next = 0; apr_socket_t *temps;") isn't
supported by all compilers and is distracting when reviewing
* suitable identifier names (e.g., fix global variable "flag" and whatever else isn't appropriate;
"ap_post_config_listeners" should be renamed to indicate what it does
* APLOGNO(99999) and comments about fixing it: Instead put "APLOGNO()" and don't add reminders
in comments
* this doesn't seem portable: "int free_slots[MAX_SPAWN_RATE/num_buckets];"
and so on


Thanks,
Yingqi


From: Lu, Yingqi
Sent: Monday, February 24, 2014 10:37 AM
To: dev@httpd.apache.org<mailto:dev@httpd.apache.org>
Subject: RE: FW: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support

Thanks very much, Jeff!

Thanks,
Lucy

From: Jeff Trawick [mailto:trawick@gmail.com]
Sent: Monday, February 24, 2014 10:36 AM
To: Apache HTTP Server Development List
Subject: Re: FW: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support

On Mon, Feb 24, 2014 at 1:20 PM, Lu, Yingqi <yingqi.lu@intel.com<mailto:yingqi.lu@intel.com>>
wrote:
Hi All,

I just want to ping again on this patch to gather your feedback and comments. Please refer
to the messages below for patch details.

Thanks,
Yingqi

Hi Yinqqi,

I'm sorry that nobody has responded yet.  I'll try to do so very soon.


From: Lu, Yingqi
Sent: Monday, February 10, 2014 11:13 AM

To: dev@httpd.apache.org<mailto:dev@httpd.apache.org>
Subject: RE: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support

I am reattaching the patch in case you missed the original email.

Thanks,
Yingqi

From: Lu, Yingqi
Sent: Monday, February 10, 2014 11:09 AM
To: dev@httpd.apache.org<mailto:dev@httpd.apache.org>
Subject: RE: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support

Hi All,

I just want to ping again on this patch to see if there are any feedback and comments. This
is our first patch to the Apache community. Please let us know if there is anything we can
do to help you test and comment the patch.

Thanks,
Yingqi

From: Lu, Yingqi
Sent: Friday, January 24, 2014 3:26 PM
To: dev@httpd.apache.org<mailto:dev@httpd.apache.org>
Subject: [PATCH ASF bugzilla# 55897]prefork_mpm patch with SO_REUSEPORT support

Dear All,

Our analysis of Apache httpd 2.4.7 prefork mpm, on 32 and 64 thread Intel Xeon 2600 series
systems, using an open source three tier social networking web server workload, revealed performance
scaling issues.  In current software single listen statement (listen 80) provides better scalability
due to un-serialized accept. However, when system is under very high load, this can lead to
big number of child processes stuck in D state. On the other hand, the serialized accept approach
cannot scale with the high load either.  In our analysis, a 32-thread system, with 2 listen
statements specified, could scale to just 70% utilization, and a 64-thread system, with signal
listen statement specified (listen 80, 4 network interfaces), could scale to only 60% utilization.

Based on those findings, we created a prototype patch for prefork mpm which extends performance
and thread utilization. In Linux kernel newer than 3.9, SO_REUSEPORT is enabled. This feature
allows multiple sockets listen to the same IP:port and automatically round robins connections.
We use this feature to create multiple duplicated listener records of the original one and
partition the child processes into buckets. Each bucket listens to 1 IP:port. In case of old
kernel which does not have the SO_REUSEPORT enabled, we modified the "multiple listen statement
case" by creating 1 listen record for each listen statement and partitioning the child processes
into different buckets. Each bucket listens to 1 IP:port.

Quick tests of the patch, running the same workload, demonstrated a 22% throughput increase
with 32-threads system and 2 listen statements (Linux kernel 3.10.4). With the older kernel
(Linux Kernel 3.8.8, without SO_REUSEPORT), 10% performance gain was measured. With single
listen statement (listen 80) configuration, we observed over 2X performance improvements on
modern dual socket Intel platforms (Linux Kernel 3.10.4). We also observed big reduction in
response time, in addition to the throughput improvement gained in our tests 1.

Following the feedback from the bugzilla website where we originally submitted the patch,
we removed the dependency of APR change to simplify the patch testing process. Thanks Jeff
Trawick for his good suggestion! We are also actively working on extending the patch to worker
and event MPMs, as a next step. Meanwhile, we would like to gather comments from all of you
on the current prefork patch. Please take some time test it and let us know how it works in
your environment.

This is our first patch to the Apache community. Please help us review it and let us know
if there is anything we might revise to improve it. Your feedback is very much appreciated.

Configuration:
<IfModule prefork.c>
    ListenBacklog 105384
    ServerLimit 105000
    MaxClients 1024
    MaxRequestsPerChild 0
    StartServers 64
    MinSpareServers 8
    MaxSpareServers 16
</IfModule>

1. Software and workloads used in performance tests may have been optimized for performance
only on Intel microprocessors. Performance tests, such as SYSmark and MobileMark, are measured
using specific computer systems, components, software, operations and functions. Any change
to any of those factors may cause the results to vary. You should consult other information
and performance tests to assist you in fully evaluating your contemplated purchases, including
the performance of that product when combined with other products.

Thanks,
Yingqi



--
Born in Roswell... married an alien...
http://emptyhammock.com/
http://edjective.org/




--
Born in Roswell... married an alien...
http://emptyhammock.com/
http://edjective.org/


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