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Re: [PATCH] Set FILE_ATTRIBUTE_TEMPORARY on files opened by mkstemp()on WinNT
On Fri, 22 Jul 2005, Christopher Faylor wrote:
> On Fri, Jul 22, 2005 at 12:28:08PM +0200, Vaclav Haisman wrote:
> >On Thu, 21 Jul 2005, Christopher Faylor wrote:
> >>On Fri, Jul 22, 2005 at 03:17:33AM +0200, Vaclav Haisman wrote:
> >>>On Thu, 21 Jul 2005, Christopher Faylor wrote:
> >>>>On Fri, Jul 22, 2005 at 01:32:50AM +0200, Vaclav Haisman wrote:
> >>>>>the attached patch sets FILE_ATTRIBUTE_TEMPORARY on files opened by
> >>>>>mkstemp() on WinNT class systems. Theoretically the OS should then be
> >>>>>less eager to write such files onto the physical storage and use cache
> >>>>>instead.
> >>>>
> >>>>Thank you for the patch but unless you can demonstrate some obvious
> >>>>performance improvements I don't think we'll be applying it. You've
> >>>>slowed down (slightly) the common case of calling open for the uncommon
> >>>>case of calling mk?temp.
> >>>
> >>>I am not sure what kind of slow down do you mean. Is it the one extra
> >>>call?
> >>
> >>It was more than one extra call, but yes.
> >>
> >>>In that case the attached modified patch should fix it. The call to
> >>>open_with_attributes() in open() gets inlined, I have checked the
> >>>resulting .s file.
> >>
> >>Can you demonstrate some obvious performance improvements? Does it
> >>speed up configure, make bash start up faster, make the rxvt window
> >>faster to show up?
> >
> >I don't think that any of the extra ifs and assignments could cause any
> >measurable slowdown. I also do not think that there are any _obvious_
> >speed ups. It is merely a hint to the cache subsystem, not a silver
> >bullet.
>
> I wasn't asking if there was a slowdown. I wanted to know the rationale
> for this change. Increasing code complexity for no obvious gain is not
> something that I want to do.
The only rationale I can offer is the docs
(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/fs/createfile.asp)
and that it makes sense.
VH