You might want to turn on slow log and see where the requests over 10ms are taking time in the request process.
-Bryan On Jan 17, 2014, at 3:29 PM, Kanishka . <kanis...@yahoo-inc.com> wrote: > Hi, > > I've been trying to configure an Apache server and ATS on a host. For us, > the latency matters more than RPS/QPS. > > We've observing a huge spike in latency for a small number of requests. > Typically, the 99.99%-ile are in tens to hundreds of ms. The 100%-ile is > often couple of single digit seconds. Where as the 50%-ile is less than 2 ms > and 99.9%-ile is nearly 5ms. Above %-iles are all based on > observations/measurements from clients side. > > In general, a unloaded server takes around 2 ms to process a request (e.g. > Time spent in the Apache module processing the request). > > In terms of RPS, the best so far has been around 2.2K RPS with 16 clients > programs and Apache (2.2) server with max client set to 31. > > We're using persistent connections between the client and the ATS and > transient/non-persistent connections between ATS and Apache. > > Apache processes are configured to served unlimited number of requests. It > uses preform MPM. [ET_NET 0] uses up to 80% or more cpu (based on top). > > The 99.9%-ile latencies worse if the number of clients exceed the no of > Apache processes. > > This is the first time I'm experimenting with ATS. Pointers towards keeping > the latency in check and maximizing the performance without impacting the > latency will be highly appreciated. Currently, the max cup utilization is > ~25%. > > Please note, I want to use ATS only as a reverse proxy and I don't intend to > use any other functionality (like caching etc). > > Thanks, > Kanishka
