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author | Jason A. Donenfeld <Jason@zx2c4.com> | 2019-08-03 20:43:16 +0000 |
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committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2019-08-04 07:06:50 +0000 |
commit | 85a8076d08d75cd939136dc01fde4a18aeb78e70 (patch) | |
tree | f44603cba636eaf5b5f5210417389886a4f1ae89 | |
parent | GetCurrentProcessToken() is Win8+, so open our own token (diff) | |
download | wintun-85a8076d08d75cd939136dc01fde4a18aeb78e70.tar.xz wintun-85a8076d08d75cd939136dc01fde4a18aeb78e70.zip |
Spin less and more efficiently
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
-rw-r--r-- | README.md | 2 | ||||
-rw-r--r-- | undocumented.h | 2 | ||||
-rw-r--r-- | wintun.c | 9 |
3 files changed, 7 insertions, 6 deletions
@@ -137,7 +137,7 @@ for (;;) { } ``` -It may be desirable to spin for ~50ms before waiting on the `TailMoved` event, in order to reduce latency. +It may be desirable to spin a short amount of time before waiting on the `TailMoved` event, in order to reduce latency. When closing the handle, Wintun will set the `Tail` to 0xFFFFFFFF and set the `TailMoved` event to unblock the waiting user process. diff --git a/undocumented.h b/undocumented.h index c904c7a..cf85823 100644 --- a/undocumented.h +++ b/undocumented.h @@ -37,3 +37,5 @@ ZwQuerySystemInformation( PVOID SystemInformation, ULONG SystemInformationLength, ULONG *ReturnLength); + +extern NTSTATUS ZwYieldExecution(VOID); @@ -402,9 +402,11 @@ _Function_class_(KSTART_ROUTINE) static VOID TunProcessReceiveData(_Inout_ TUN_CTX *Ctx) { + KeSetPriorityThread(KeGetCurrentThread(), 1); + TUN_RING *Ring = Ctx->Device.Receive.Ring; ULONG RingCapacity = Ctx->Device.Receive.Capacity; - const ULONG SpinMax = 10000 * 50 / KeQueryTimeIncrement(); /* 50ms */ + const ULONG SpinMax = 10000 * 20 / KeQueryTimeIncrement(); /* 20 ms */ VOID *Events[] = { &Ctx->Device.Disconnected, Ctx->Device.Receive.TailMoved }; ASSERT(RTL_NUMBER_OF(Events) <= THREAD_WAIT_OBJECTS); @@ -431,10 +433,7 @@ TunProcessReceiveData(_Inout_ TUN_CTX *Ctx) KeQueryTickCount(&SpinNow); if ((ULONG64)SpinNow.QuadPart - (ULONG64)SpinStart.QuadPart >= SpinMax) break; - - /* This should really call KeYieldProcessorEx(&zero), so it does the Hyper-V paravirtualization call, - * but it's not exported. */ - YieldProcessor(); + ZwYieldExecution(); } if (RingHead == RingTail) { |