Am 24.04.2013 05:44, schrieb Liu James: > Dear all, > > I used Valgrind(callgrind) to profile database cache performance, and > the host machine is a VM guest with XEON CPU. > > Without instrumentation, the performance of dbms with cache-on is 20% > higher
What do you mean by higher? Better or worse performance? than cache-off. With callgrind, the call graph shows there is a > 5x performance improvement. For Callgrid/Cachegrind, the environment doesn't matter as it's a simulation of a simple cache hierarchy, only takeing user level into account. So it does not matter if it's running within a VM guest. BUT: I would assume that user-level simulation can not really capture what's going on in a database, as there probably is much I/O and the OS involved, and more important, the performance probably depends on external latency/bandwidth contrains from network/drives etc. > My point is whether Valgrind is suitable for profiling working in VM? > e.g, with IR conversion, the performance gap becomes larger, which > does not reflect the real gap. If you are familiar with profiling, I > appreciate you could recommend some other profile tools. Any profiler which does system-wide sampling should be fine (perf, oprofile, other Intel/AMD tools, ...). But the VM must support to pass performance counters to guests, if that tool should work in the guest. I think that perf running within a KVM guest should be able to do this. Interpreting the results is another issue. An idea would be to check how much the performance depends on external constrains. A VM should allow to throttle e.g. the network connection. On the other hand - as John suggested - why not get rid of the VM for profiling first? More tools should work, and you also can compare results with/without VM afterwards. The VM may play a role if a lot of TLB misses are involved - even with hardware support (extended/nested page tables) a TLB miss may be way slower in a VM guest. Josef > > > Thanks a lot!!! > > > Best regards, > James > > > ------------------------------------------------------------------------------ > Try New Relic Now & We'll Send You this Cool Shirt > New Relic is the only SaaS-based application performance monitoring service > that delivers powerful full stack analytics. Optimize and monitor your > browser, app, & servers with just a few lines of code. Try New Relic > and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr > > > > _______________________________________________ > Valgrind-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/valgrind-users > ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr _______________________________________________ Valgrind-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/valgrind-users
