Fwd: review(XXS): 7060842: UseNUMA crash with UseHugreTLBFS running SPECjvm2008

Ramki Ramakrishna y.s.ramakrishna at oracle.com
Wed Aug 3 14:58:35 PDT 2011



On 8/3/2011 2:47 PM, Igor Veresov wrote:
> On 8/3/11 2:33 PM, Ramki Ramakrishna wrote:
>> Yikes... a Linux man page i found does not say anything about swap
>> reservation:
>>
>> *MADV_DONTNEED*
>>     Do not expect access in the near future. (For the time being, the
>>     application is finished with the given range, so the kernel can free
>>     resources associated with it.) Subsequent accesses of pages in this
>>     range will succeed, but will result either in re-loading of the
>>     memory contents from the underlying mapped file (see *mmap*()) or
>>     zero-fill-on-demand pages for mappings without an underlying file.
>
> That's MADV_DONTNEED, we tried to use MADV_FREE, but there's nothing 
> about it's semantics either with regard to reservations.

Yr webrev shows DONT_NEED as the previous version in Linux. (Perhaps you 
are confusing with Solaris
where you do an MADV_FREE perhaps?)

>>
>> Is there an understanding that this is a Linux bug? Or is "resources"
>> above open to
>> interpretation, including swap reservation? (Andrew Haley?)
>>
>
> I don't know if this is intentional. madvise() has notoriously 
> different interpretations of its options under different OSes.

yeah, perhaps we want the Unix committees of the 1980s back again? 
(careful what we wish for?)

> ...
>>
>> PS: Igor, what does "louses" below (in yr email) mean in this context?
>
> Eh, that's a typo, I meant "looses".

duh, me! :-)

-- ramki


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