Re: udp performance on Windows XP
Hi, Kevin,
Thanks for your response.
I made a little further investigation today and I found the reason is that the UDP sending on Windows XP is blocked for too long a time such that even though there is no inter-packet delay, the highest speed is still only about 50Mbps.
I dont understand the reason now and I failed to find any helpful information on Google.
Anyway, please let me know if you guys find out the problem in future. By the way, I think the gettimeofday can be simply simulated by QueryPerformanceCounter() and QueryPerformanceFrequency() APIs on Windows.
Thanks and regards,
Gu
Kevin Gibbs <kgibbs --at-- ncsa.uiuc.edu> wrote:
>On Mon, 8 Dec 2003, lilyco wrote:
>> Hi, has anyone ever met such problem that, on Windows XP, the UDP
>> sending rate of Iperf is very slow?
>>
>> I have 2 machines connected by 1GigE link. Both have 2 2.4G Xeon CPU,
>> and one is running Linux, the other is running XP. When I test UDP
>> performance between these 2 machines, the throughput from Linux to XP is
>> very good, but the reverse direction can only reach about 50Mbps. The
>> TCP throughputs are both very well on two directions.
>>
>> Any ideas?
>>
>> Thanks a lot,
>> Gu
>
>You may be experiencing the lack of granularity of the
>GetSystemTimeAsFileTime on Win32 which is used for the replacement of
>gettimeofday which Win32 does not implement. This function has a large
>granularity 10ms, I believe, where gettimeofday on most *nixs will get you
>around a granularity of 10us. Unfortunately we have not had the time to
>rewrite the gettimeofday replacement for Win32 to use a Win32 Performance
>Timer rather than the GetSystemTimeAsFileTime function.
>
>Kevin
>
>
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