Re: Off-heap row cache and mmapped sstables
Absolutely. Best practice is still to disable swap entirely on server machines; mlockall is just our best attempt to at least keep your JVM from swapping if you've forgotten this. On Thu, Apr 12, 2012 at 11:15 AM, Omid Aladini omidalad...@gmail.com wrote: Hi, Cassandra issues an mlockall [1] before mmap-ing sstables to prevent the kernel from paging out heap space in favor of memory-mapped sstables. I was wondering, what happens to the off-heap row cache (saved or unsaved)? Is it possible that the kernel pages out off-heap row cache in favor of resident mmap-ed sstable pages? Thanks, Omid [1] http://pubs.opengroup.org/onlinepubs/007908799/xsh/mlockall.html -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
Re: Off-heap row cache and mmapped sstables
On 4/12/12, Omid Aladini omidalad...@gmail.com wrote: Cassandra issues an mlockall [1] before mmap-ing sstables to prevent the kernel from paging out heap space in favor of memory-mapped sstables. I was wondering, what happens to the off-heap row cache (saved or unsaved)? Is it possible that the kernel pages out off-heap row cache in favor of resident mmap-ed sstable pages? For what it's worth, I find this conjecture plausible given my understanding of the Cassandra ticket which resulted in the use of JNA+mlockall. I'd love to hear an opinion from someone from the project with more in-depth knowledge. :) =Rob -- =Robert Coli AIMGTALK - rc...@palominodb.com YAHOO - rcoli.palominob SKYPE - rcoli_palominodb
Off-heap row cache and mmapped sstables
Hi, Cassandra issues an mlockall [1] before mmap-ing sstables to prevent the kernel from paging out heap space in favor of memory-mapped sstables. I was wondering, what happens to the off-heap row cache (saved or unsaved)? Is it possible that the kernel pages out off-heap row cache in favor of resident mmap-ed sstable pages? Thanks, Omid [1] http://pubs.opengroup.org/onlinepubs/007908799/xsh/mlockall.html
