Re: [PATCH] Use MAP_HUGETLB where supported (v3)

On 2013-10-24 16:06:19 +0300, Heikki Linnakangas wrote:
> On 24.10.2013 09:03, Abhijit Menon-Sen wrote:
> >One open question is what to do about rounding up the size. It should
> >not be necessary, but for the fairly recent bug described at the link
> >in the comment (https://bugzilla.kernel.org/show_bug.cgi?id=56881). I
> >tried it without the rounding-up, and it fails on Ubuntu's 3.5.0-28
> >kernel (mmap returns EINVAL).
>
> Let's get rid of the rounding. It's clearly a kernel bug, and it shouldn't
> be our business to add workarounds for any kernel bug out there. And the
> worst that will happen if you're running a buggy kernel version is that you
> fall back to not using huge pages (assuming huge_tlb_pages=try).

But it's a range of relatively popular kernels, that will stay around
for a good while. So I am hesitant to just not do anything about it. The
directory scanning code isn't that bad imo.

Either way:
I think we should log when we tried to use hugepages but fell back to
plain mmap, currently it's hard to see whether they are used.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services