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From Jonathan Ellis <>
Subject Re: mmap
Date Thu, 15 Jul 2010 21:52:39 GMT
On Thu, Jul 15, 2010 at 3:56 PM, Carlos Alvarez <> wrote:
> On Thu, Jul 15, 2010 at 2:01 PM, Jonathan Ellis <> wrote:
>> The main problem is not the syscall so much as Java insisting on
>> zeroing out any buffer you create, which is a big hit to performance
>> when you're allocating buffers for file i/o on each request instead of
>> just mmaping things.  Re-using those buffers would be possible but
>> difficult; I think using mlockall to "fix" the mmap approach is more
>> promising.
> Sorry if it is a silly question, but what would be the approach? issue
> a mlockall with the current set (MLC_CURRENT) before mmap the files?


> Did someone have an opinion on that
> ?.
> Do you think it could be useful for cassandra to arrange things in the
> files in order to try to have that kind of 'page afinity' in the data
> and minimize the page faults trasversing the data?

that's exactly what the sstable index design is already doing

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support

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