Re: Hugetables question

On Wed, 22 Jun 2011 14:24:17 +0300, Marti Raudsepp wrote:
> On Sun, Jun 19, 2011 at 12:56, Radosław Smogura
> <rsmogura@softperience.eu> wrote:
>> I want to implement hugepages for shared memory
>
> Hi,
>
> Have you read this post by Tom Lane about the performance estimation
> and a proof-of-concept patch with hugepages?
> http://archives.postgresql.org/pgsql-hackers/2010-11/msg01842.php
>
> It's possible that there was a flaw in his analysis, but his
> conclusion is that it's not worth it:
>
>> And the bottom line is: if there's any performance benefit at all,
>> it's on the order of 1%.  The best result I got was about 3200 TPS
>> with hugepages, and about 3160 without.  The noise in these numbers
>> is more than 1% though.
>
> Regards,
> Marti
Actually when I tried to implement hugepages for palloc (I ware unable to write fast and effective mallocator), my
resultwas that when I was using normal pages I got small performance degree, but when I was using huge pages this was
fasterthen normal build (even with infective mallocator).
 
I know there are some problems with accessing higher memory (when server is more then 8GB), and hugepages may resolve
this.
I strictly disagree with opinion if there is 1% it's worthless. 1% here, 1% there, and finally You get 10%, but of
coursehugepages will work quite well if will be used in code that require many random "jumps". I think this can be
reproducedand some not-common case may be found to get performance of about 10% (maybe upload whole table in shared
bufferand randomly "peek" records one by one).
 
Regards,Radek