Re: Much improved sendfile(2) kernel implementation

On Sat, 23 Sep 2006, Andre Oppermann wrote:

>> Without patch:
>>  87380 393216 393216    10.00      2163.08   100.00   19.35    3.787 
>> 1.466 Without patch + TSO:
>>  87380 393216 393216    10.00      4367.18   71.54    42.07    1.342 
>> 1.578 With patch:
>>  87380 393216 393216    10.01      1882.73   86.15    18.43    3.749 
>> 1.604 With patch + TSO:
>>  87380 393216 393216    10.00      6961.08   47.69    60.11    0.561 
>> 1.415

The impact of TSO is clearly dramatic, especially when combined with the 
patch, but I'm a bit concerned by the drop in performance in the patched 
non-TSO case.  For network cards which will always have TSO enabled, this 
isn't an issue, but do we see a similar affect for drivers without TSO?  What 
can we put this drop down to?

Robert N M Watson
Computer Laboratory
University of Cambridge