4 ms·
Amazon doesnt expose much of these statistics (how fast of ram do i get with a M3.large or a c3.med etc) . Does this mean real performance is for those who own
by maerF0x0 12y ago
Amazon doesnt expose much of these statistics (how fast of ram do i get with a M3.large or a c3.med etc) . Does this mean real performance is for those who own their servers?
- wmf 12y agoRAM performance is the same for VMs and bare metal. And the ~1.5x performance difference between different grades of DRAM (e.g. 1333 vs. 1600 vs. 2133 MHz) is negligible compared to the massive cache-RAM and RAM-flash gaps. And speaking of cache, lstopo (from the hwloc package) does work correctly under EC2.
- lgeek 12y agoIt may be the same in the sense that hypervisors don't explicitly limit it, but on a multicore host you're sharing memory bandwidth with the other guests, in the common(?) case when the host has more cores than a guest. You can also experience increased latency when there is access contention.
- wmf 12y agoTrue, if you want full and predictable memory/cache performance you need to rent a full-machine VM (usually 8xlarge) or bare metal.
- lallysingh 12y agoIt's easy enough to find out. Create an array of linked-list nodes, and have them point to each other randomly (hint: std::random_shuffle w/an array of indices). Write a routine that traverses the list N times. Time the routine for larger lists. You should see a jump as your list gets larger than each stage of cache.
- maerF0x0 12y agoSeems to me that would be very dependent on neighbours and their current workloads?