Re: [PATCH] Use MAP_HUGETLB where supported (v3) - Mailing list pgsql-hackers

From Heikki Linnakangas
Subject Re: [PATCH] Use MAP_HUGETLB where supported (v3)
Date
Msg-id 5310CADC.1000209@vmware.com
Whole thread Raw
In response to Re: [PATCH] Use MAP_HUGETLB where supported (v3)  (Christian Kruse <christian@2ndQuadrant.com>)
Responses Re: [PATCH] Use MAP_HUGETLB where supported (v3)  (Peter Geoghegan <pg@heroku.com>)
Re: [PATCH] Use MAP_HUGETLB where supported (v3)  (Christian Kruse <christian@2ndQuadrant.com>)
List pgsql-hackers
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



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