Request for review (XS): 8006431: os::Bsd::initialize_system_info() sets _physical_memory too large

[Staffan Larsen]

Looks good!

/Staffan

On 18 jan 2013, at 07:36, Bengt Rutisson <bengt.rutisson at oracle.com> wrote:

> 
> Hi all,
> 
> Could I have a couple of reviews for this small fix?
> 
> http://cr.openjdk.java.net/~brutisso/8006431/webrev.00/
> 
> On OSX we used HW_USERMEM value from sysctl() to get the available physical memory on the machine. This is a 32 bit value but we store it in a 64 bit variable. This means that we get kind of random and normally very large values for what we think the physical memory is.
> 
> We actually don't want a 32 bit value since we want to handle machines with more than 2 or 4 GB of memory. Instead of HW_USERMEM we should be using HW_MEMSIZE which will give us a 64 bit value.
> 
> See:
> https://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man3/sysctl.3.html
> 
> Thanks Staffan Larsen for both detecting the problem and providing a solution.
> 
> This is a one-word-change. So, to save you a mouse click on the webrev link above, here is the diff:
> 
> --- a/src/os/bsd/vm/os_bsd.cpp
> +++ b/src/os/bsd/vm/os_bsd.cpp
> @@ -260,7 +260,7 @@
>     * instead of hw.physmem because we need size of allocatable memory
>     */
>    mib[0] = CTL_HW;
> -  mib[1] = HW_USERMEM;
> +  mib[1] = HW_MEMSIZE;
>    len = sizeof(mem_val);
>    if (sysctl(mib, 2, &mem_val, &len, NULL, 0) != -1)
>         _physical_memory = mem_val;
> 
> Thanks,
> Bengt
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