Stupid question

[Greg Bowyer]

Yes thats basically it

java -Xms512m -Xmx9g test

On 22/05/12 12:27, Vitaly Davidovich wrote:
>
> Hi Greg,
>
> As an aside, in os::commit_memory, I think the tertiary condition that 
> sets the flags is inverted - you want MAP_LOCKED if LockHeapInMemory 
> is set, I believe.
>
> As to your question, what args are being passed to the above function 
> in your run? I take it -Xms is less than Xmx in your trial?
>
> Sent from my phone
>
> On May 22, 2012 3:07 PM, "Greg Bowyer" <gbowyer at fastmail.co.uk 
> <mailto:gbowyer at fastmail.co.uk>> wrote:
>
>     Not sure if this is the right venue for this, or if I am insane
>
>     I have been playing with the openjdk code with a view to lock the
>     heap in memory (or at least suggest to the OS that it wants to be
>     locked in memory).
>
>     My use case is for java processes that are greedy in memory and
>     typically have a virtual size larger than physical ram. This is
>     not where an end user allocates a java heap beyond ram but rather
>     things like Lucene / Cassandra, where typically the JVM heap is
>     large but limited to say 1/4 of the total physical ram and the
>     rest of the process virtual size is taken up with mmap()'d files.
>
>     There are java projects that currently do this with a call out via
>     JNA / JNI to mlockall()
>
>     Asking the OS to use the MAP_LOCKED flag in the mmap calls in
>     os_linux.cpp effectively does an mlock / mlockall which I think
>     means that when the OS chooses pages to page out; then it should
>     (for some measure of should) avoid paging out the JVM heap.
>
>     This means that horrors between CMS and paging do not cause
>     hateful pauses (hopefully)
>
>     The thing I cant understand is that when I start a new VM with
>     this code (attached) it appears to lock the full size of the heap
>     (-Xmx) (even though the given memory is not used by the VM), this
>     seems to make the entire space resident.
>
>     any ideas ?
>
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