Re: [Windows,PATCH] Use faster, higher precision timer API

On 09/17/2014 12:51 PM, Andres Freund wrote:
> On 2014-09-17 11:19:36 -0400, Andrew Dunstan wrote:
>> On 09/17/2014 08:27 AM, Craig Ringer wrote:
>>> Hi all
>>>
>>> Attached is a patch to switch 9.5 over to using the
>>> GetSystemTimeAsFileTime call instead of separate GetSystemTime and
>>> SystemTimeToFileTime calls.
>>>
>>> This patch the first step in improving PostgreSQL's support for Windows
>>> high(er) resolution time.
>>>
>>> In addition to requiring one less call into the platform libraries, this
>>> change permits capture of timestamps at up to 100ns precision, instead
>>> of the current 1ms limit. Unfortunately due to platform timer resolution
>>> limitations it will in practice only report with 1ms resolution and
>>> 0.1ms precision - or sometimes even as much as 15ms resolution. (If you
>>> want to know more, see the README for
>>> https://github.com/2ndQuadrant/pg_sysdatetime).
>>>
>>> On Windows 2012 and Windows 8 I'd like to use the new
>>> GetSystemTimePreciseAsFileTime call instead. As this requires some extra
>>> hoop-jumping to safely and efficiently use it without breaking support
>>> for older platforms I suggest that we start with just switching over to
>>> GetSystemTimeAsFileTime, which has been supported since Windows 2000.
>>> Then more precise time capture can be added in a later patch.
>>>
>>>
>>
>> That will presumably breaK XP.
> The proposed patch? I don't really see why? GetSystemTimeAsFileTime() is
> documented to be available since win2k?


Oh, hmm, yes, you're right. For some reason I was thinking W2K was later 
than XP. I get more random memory errors as I get older ...

cheers

andrew