Arun Sharma <[email protected]> writes: > On 1/21/12 7:24 AM, Mark Callaghan wrote: >> 1 millisecond per thread would be much better than what we experience >> today. >> > > Is there a reason why latency per-thread is more interesting than the > absolute number?
You are right of course - the interesting number is the time we spent with the target mysqld process suspended (stalled) under ptrace(). The reason I think in terms of latency-per-thread is this: Different mysqld instances can have widely different number of threads - from a few handful to perhaps thousands. Since we loop over threads while the process is ptrace()-suspended, it seems a nice measure to estimate the cost independent of number of threads in the process. >>> Arun: What I've done so far is mostly to cache reads of the same word, and >>> delay name resolve to after the target process is resumed. I think it can >>> be >>> made even faster by reading target process memory through /proc/PID/mem >>> instead of ptrace and if we can reduce repeated reads of /proc/PID/maps >>> and >>> such. > > Sounds like a good optimization to have. There is already a cache > internal to libunwind that maps a given IP address to it's unwind > info. If the repeated reads come from that code path, tweaking the > cache size might be a simpler fix. Ok, that sounds cool! - Kristian. _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
