review request for 6673124

David Holmes - Sun Microsystems David.Holmes at Sun.COM
Sun Oct 5 17:44:14 PDT 2008

Looks good to me.


Xiaobin Lu said the following on 10/05/08 04:32:
> Webrev:
> Details:
> Hotspot needs to compute the number of available CPUs available to the 
> java process in order to determine which flavor of VM to be used or how 
> many GC threads needs to created for parallel collector. Also, the user 
> could call Runtime.availableProcessors() and use that result to 
> determine how many threads needs to be created for their applications, etc.
> Here is the current way to compute that number on Solaris where the 
> problem might be seen. First, we check whether the process is bound to a 
> existing processor set, if yes, we then check how many processors inside 
> that processor set and use that number as the available CPUs. If not, we 
> just return the number of total online CPUs as the number of available 
> CPUs. This ignores the fact that even the process is NOT running inside 
> a processor set, however, if there is any processor set around, the CPUs 
> in that processor set won't be available to the java process. So the 
> correct way of doing this is to ignore whether the process is bound to a 
> processor set or not, as long as "pset_bind" returns successfully, we 
> then use "pset_info" to check the available CPUs to us.
> We decided not to invent another flag to fall back to the old behavior 
> which is absolutely wrong. Plus it is hard to come up with a sensible 
> name for that flag, not to mention the user has to dig through 
> globals.hpp to find out that flag to use.
> Reviewed by:
> Verified by:
> Experiments made on multi-core Solaris machines and trace put in the 
> code to verify the return value is correct.
> Thanks,
> -Xiaobin

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