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Date:      Sat, 17 Oct 2009 08:58:23 -0700
From:      Chuck Swiger <cswiger@mac.com>
To:        Steve Dong <sdong@huawei.com>
Cc:        freebsd-performance@freebsd.org
Subject:   Re: Comparison of FreeBSD/Linux TCP Throughput performance
Message-ID:  <0D9BF9F3-FDA1-4111-9E6C-733E1FD972F5@mac.com>
In-Reply-To: <000001ca4f3c$78dc3550$6501a8c0@china.huawei.com>
References:  <78DB4AE8EF5F4A1EBD3992D7404B2725@china.huawei.com> <b8592ed80910150512k6d334f89s3fa308a85e19da9e@mail.gmail.com> <4831593800614E6796A45F20BA4B818E@china.huawei.com> <001301ca4e23$b96e35b0$3322c10a@china.huawei.com> <001c01ca4e24$f10f6e70$3322c10a@china.huawei.com> <20091016075336.03eb17f2.wmoran@collaborativefusion.com> <000001ca4f3c$78dc3550$6501a8c0@china.huawei.com>

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Hi, Steve--

On Oct 17, 2009, at 8:14 AM, Steve Dong wrote:
> If there's a better/lighter way to show these graphics, I'd like to  
> know.

Sure-- put 'em on a webserver somewhere, and put links to them in your  
email to this mailing list.

If you wanted to do even better than that, set up a simple webpage  
describing what you are doing in your comparison, have a link to the  
dmesg/boot output for each platform as a .txt file and a description  
of any system tweaks & tuning, have a link that points to a  
description of the test setup (ie, your ASCII diagram of the switch  
and 4 machines), then your graphs, then the raw data (or links to it,  
depending).  You can then throw in netstat -s output, or NIC driver  
stats from sysctl, or switch stats, etc-- anything else that adds  
useful context.

There are a fair number of posts in the list archives which describe  
how to benchmark reliably, and the people who are most likely to be  
making code changes to FreeBSD also tend to like to know whether  
you've collected enough data, in a controlled fashion, to have an idea  
as to whether your measurements are reproducible.  I'm not a purist,  
and I believe you can get useful estimations without rigorous testing,  
but there are others who make the point that if you haven't provided  
at least a standard deviation, then you haven't collected enough  
data-- done enough trials-- to determine whether the results are  
meaningful.   (See /usr/src/tools/tools/ministat/README)

Of course, you're not obligated to do any of the above, but if you  
want the effort you've put in to be more useful, consider these a  
suggestion.  Finally, the next step beyond that would be to try  
tweaking some things, and see what kind of changes you get from that  
versus the original performance.  It might be the case that making a  
simple tuning change would have a significant difference in  
performance; if you can identify that, then FreeBSD or Linux  
developers can use that information to better tune the OS defaults.

Regards,
-- 
-Chuck




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