Re: Winsock select timeout

From:

"Ben Voigt [C++ MVP]" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 18 Oct 2007 09:41:50 -0500

Message-ID:

<#FMf$TZEIHA.5328@TK2MSFTNGP05.phx.gbl>

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp> wrote in message
news:eLHaXKOEIHA.1316@TK2MSFTNGP02.phx.gbl...

"Mark Salsbery [MVP]" <MarkSalsbery[MVP]@newsgroup.nospam> wrote in
message news:eMnp%23sNEIHA.5752@TK2MSFTNGP02.phx.gbl...

but the thread switching period is probably 20 milliseconds.

Hi Scott,

I'm curious, where did you get that number from? That seems like a really
long time and it makes me wonder how my multimedia software works at all
:) Is it really that long?

Cheers,
Mark

The system timer interrupt interval is available from
GetSystemTimeAdjustment(). If my memory is right it was 20 msec for
NT/2K/XP. On my Vista machine it returns 15 msec.

Timer-based thread switching can't go faster than the system timer. But
who knows, with multimedia I/O they may have souped it up to do a thread
switch upon a multimedia interrupt. Sound cards don't need much help
though, because they contain hardware buffering that greatly reduces the
interrupt rate.

Multimedia software often calls timeBeginPeriod/timeEndPeriod to get a
faster timer interrupt interval, as low as 1ms.

--
Scott McPhillips [VC++ MVP]