Re: BUG #17448: In Windows 10, version 1703 and later, huge_pages doesn't work.

On Thu, Mar 31, 2022 at 04:42:37PM +0900, Michael Paquier wrote:
> On Thu, Mar 31, 2022 at 12:59:08PM +0800, Julien Rouhaud wrote:
> > That approach seems sensible.  For reference the versionhelpers.h seems to be
> > available starting with VS 2013 / v120, which is ok since that the oldest
> > version we support AFAICS.
> 
> Hmm.  This points out to a different problem.  The oldest version of
> MSVC supported on v10 and v11 is VS2005, so a backpatch means that
> those checks would need to be tweaked if we'd want to be perfectly
> compatible.  But I'd rather not enter in this game category, limiting
> this patch to v12~ :)

Ah, I indeed haven't check in back branches.  v12 isn't that bad.

> > Now, I also have the exact same result without the patch applied so it's hard
> > to know whether it had any impact at all.  Unfortunately, I didn't find any
> > information on how to check if "large pages" are used and/or by which program.
> 
> Okano-san has mentioned VMMap upthread:
> https://docs.microsoft.com/en-us/sysinternals/downloads/vmmap

Yes, I totally missed that.  Thomas Munro also mentioned it off-list, and
also found some reference [1] indicating that large pages should show up as
"Locked WS".  I tested with and without the patch and in both case I don't see
any "Locked WS" usage.  I also get the same Page Table size, which seems
consistent with large pages not being used.  Now, this is a vm running with
virtualbox and we're not entirely sure that huge pages can be allocated with
it.  I wish I could test on my windows 10 machine as it's not virtualized, but
I can't give the required privileges.

[1] https://aloiskraus.wordpress.com/2016/10/03/windows-10-memory-compression-and-more/