David O'Brien wrote: > On Sun, Oct 30, 2005 at 02:39:40PM +0800, David Xu wrote: > >>David O'Brien wrote: >> >>>On Fri, Oct 28, 2005 at 03:34:57PM +0200, Alexander Leidinger wrote: >>> >>>>I don't have the message at hand. I just had time to write the mail, but I >>>>don't have my laptop with me to reproduce the message. But it's easy to >>>>reproduce, just take a PC which is able to make use of powerd and switch >>>>to >>>>using TSC as the timecounter. >>> >>>What is the motivation to use the TSC as a timecounter? >> >>TSC is faster than any others, on many systems, so-called ACPI-fast >>timer is really a slow chip, > > > Correct, but why is it felt the latency of the ACPI timer is an issue? > Of course we all want things to as fast as possible, but is that just an > abstract desire, or a real issue was run into? > ACPI-fast requires an ioport read which takes about 1us (according to Google). Do that 1000 times a second and you have each CPU spending 1% of its time doing nothing but reading the clock. Yikes. ScottReceived on Sun Oct 30 2005 - 13:30:41 UTC
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