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

On 02/27/2014 09:34 AM, Christian Kruse wrote:
> Hi,
>
> On 26/02/14 13:13, Alvaro Herrera wrote:
>>
>> There's one thing that rubs me the wrong way about all this
>> functionality, which is that we've named it "huge TLB pages". That is
>> wrong -- the TLB pages are not huge. In fact, as far as I understand,
>> the TLB doesn't have pages at all. It's the pages that are huge, but
>> those pages are not TLB pages, they are just memory pages.
>
> I didn't think about this, yet, but you are totally right.
>
>> Since we haven't released any of this, should we discuss renaming it to
>> just "huge pages"?
>
> Attached is a patch with the updated documentation (now uses
> consistently huge pages) as well as a renamed GUC, consistent wording
> (always use huge pages) as well as renamed variables.

Hmm, I wonder if that could now be misunderstood to have something to do
with the PostgreSQL page size? Maybe add the word "memory" or "operating
system" in the first sentence in the docs, like this: "Enables/disables
the use of huge memory pages".

> <para>
> At present, this feature is supported only on Linux. The setting is
> ignored on other systems when set to <literal>try</literal>.
> <productname>PostgreSQL</productname> will
> refuse to start when set to <literal>on</literal>.
> </para>

Is it clear enough that PostgreSQL will only refuse to start up when
it's set to on, *if the feature's not supported on the platform*?
Perhaps just leave that last sentence out. It's mentioned later that "
With <literal>on</literal>, failure to use huge pages will prevent the
server from starting up.", that's probably enough.

- Heikki