Steven Grimm wrote: > Darpan Dinker wrote: >> Can somebody provide a ballpark response time for a get( ) under light >> load for: >> - a memcached server on the same system as the client >> - a remove server with 1 Gigabit Ethernet network >> >> I am guessing that it is on the order of 20ms and 150ms. >> >> Feedback appreciated; please include the processor, memory size and OS. >> Darpan >> > > Something is seriously wrong with your configuration if you're seeing > anything like 20ms response times. It should be more like 0.5ms for > remote hosts and 0.05ms for localhost. I hope that really was just a > wild guess, not the result of actual testing. My mistake in typing the units, I was thinking more in terms of 20us and 150us. Your numbers are ~40us and ~500us. I appreciate your reply. Darpan > > For simple single-key "get" requests over TCP, we typically see > between 400 and 500 microsecond response times. That's for a remote > host over a gigabit Ethernet, both the client and the server running > Linux 2.6 kernels on 4-core 1.8GHz AMD64 boxes. If I run memcached on > the same box as my client, I see 35-40 microsecond response times. > > The memory size is irrelevant (memcached uses a self-expanding > hashtable which provides constant-time lookups regardless of cache > size) but the OS matters. In our tests we found, for example, that > Solaris had somewhat higher latency than Linux on the same hardware. > On the order of 50-100usec, if I remember correctly, but it was a > while ago so the gap may have closed in the meantime. > > CPU type matters too: SPARC boxes had *much* higher latency than AMD64 > ones, no surprise since each core of a big multicore SPARC box is > significantly slower than each core of an AMD64 box (even if the total > number of computations per second is much greater on the SPARC due to > its high parallelism.) I don't remember the numbers on that one -- > maybe some of the Sun guys can pipe up on this front? > > Oh, the other thing that matters is your client. If you are using a > client in a slow language, your apparent response time will of course > be higher by some amount, but that's nothing to do with memcached per > se. Likewise, if your client has to do object deserialization when it > gets a response back, that may also affect response time depending on > how fast your language's serialization is. Though I have never > encountered any language where deserialization time would be measured > in tens of milliseconds on modern hardware! > > -Steve > >
-- Blog: http://darpanetwork.blogspot.com/ Atom: http://darpanetwork.blogspot.com/feeds/posts/default
