[Winpcap-bugs] Potential waste of NonPaged kernel buffer space on Hyper-Threading machines in the NPF Driver?

Gadi Elishayov haxorcize at gmail.com
Sat May 23 12:33:28 PDT 2009

I've conducted some tests on an Hyper-Threading enabled machine with 2
Physical CPUs and I found out that NdisSystemProcessorCount() returns 4
(that is due to the virtual cpu).
Also, to my understanding, in the HT technology, only one CPU out of a pair
of 2 virtual will ever handle interrupts.
The code in the NPF driver uses this value to divide its per-CPU buffer,
but given the fact that only half of the processors handle interrupts, the
buffer itself is wasted on those CPUs who don't handle interrupts.
Am I wrong?
Is there a way to fix this besides making a single buffer for the entire
Maybe some good way to know which CPUs will handle interrupts, drain the DPC
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