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Re: BUG #2406: Not all systems support SHM_SHARE_MMU

From: Paul van der Zwan <Paul(dot)Vanderzwan(at)Sun(dot)COM>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #2406: Not all systems support SHM_SHARE_MMU
Date: 2006-04-25 07:31:46
Message-ID: 6FEB09EB-03D6-48A9-9580-541753F88E8C@Sun.COM (view raw or whole thread)
Lists: pgsql-bugs
On 25-apr-2006, at 9:08, Tom Lane wrote:

> Paul van der Zwan <Paul(dot)Vanderzwan(at)Sun(dot)COM> writes:
>> Maybe noone ever ran Postgres on Solaris on a VIA Epia system.
> Maybe.  What is a "VIA Epia system"?

VIA is a hardware manufacturer who make small, low power boards with  
their own X86 compatible cpu
on it, you can find more about it on : 

> Frankly, I'm afraid that your patch is likely to break way more  
> systems
> than it fixes.  What is getpagesizes(), and is it guaranteed to  
> exist on
> *every* Solaris system?  What the heck correlation does its result  
> have
> to whether SHM_SHARE_MMU will work?

AFAIK getpagesizes() appeared in 2001 so that probably means it is  
missing in anything before
Solaris 9.

If you look at line 308 of 
you'll see that shmat return EINVAL if only one pagesize is available.
Which is what happens on my  system, and possibly also on older (32  
bit pre Ultra ) Sparc systems.

My guess is that all UltraSparce and 'modern' x86/amd64 cpu's support  
large pages and therefor will n
ever hit this failure mode of shmat().
I'll see if I can get the x86 experts here to have a look at it...



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