On Wed, 28 Sep 2016, Allen Samuels wrote: > Boost::pool works very well when you're allocated "same" sized objects. > That's not our situation, we're allocating lots of different sized > objects -- some small, some large. The only way that Boost::pool > supports that situation is to use the "ordered_free" operation to keep > the freelist sorted (if you don't use it then you'll get fragmentation > that'll prevent allocation of large objects -- even though there's > plenty of free memory). The implementation of the sorted freelist is > O(N). Which should work well for small pools, but that's the exact > opposite of the desired use for Ceph, we're targeting large pools (think > 1GB). > > I didn't word it very well, but my proposal doesn't actually change the > underlying malloc/free algorithm, rather it's intended to put some > statistics around memory usage so that we can self-trim our memory > pools. We were doing some heap profiling yesterday and one interesting thing is that the utilized heap reported by tcmalloc is about 1/2 the RSS. We probably want to consider creating separate pools for the handful of objects that are consuming the bulk of the heap. We did this a few years back in the MDS and IIRC it helped significantly with memory utilization there. sage -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
