On 24/10/2018 21:54, Gregory Farnum wrote: > Do we understand why debug mode got so much slower? Is there something > we can do to improve it? I believe the reason for the slowdown is due to the increase of number of functions that are used in the new implementation. While in the previous implementation, the state machine was implemented with just two big functions (with a switch/case block in each), the new implementation uses one function per protocol state. I'm not familiar with what the compiler generates in Debug mode, but I imagine that now there are much more debug symbols to track, and less optimizations that the compiler can preform without confusing the debugger tools. I currently don't see a way to improve the performance in Debug mode. One thing we can do though is to also check the performance when compiling in RelWithDebugInfo mode. If it preforms similar to the Release mode, at least we still have debug symbols to help in identifying some problems. > > We are for instance seeing new issues with the messenger in our > testing, apparently because the reduced speed opens up race conditions > much wider. In this case that's good for us, but it could easily go > the other way as well and I'm concerned about not finding new issues > in our testing if the difference is so substantial compared to what > will be deployed by users. Maybe we can build packages for the binaries compiled with the two modes (Debug and Release) and be able to specify which one to use in each test run. > -Greg > On Wed, Oct 24, 2018 at 3:18 AM Yan, Zheng <ukernel@xxxxxxxxx> wrote: >> >> Only ceph complied in debug mode has the regression. Ceph complied in >> release mode has no regression. Sorry for the noisy. >> >> Yan, Zheng >> >> >> >> On Wed, Oct 24, 2018 at 1:46 PM Yan, Zheng <ukernel@xxxxxxxxx> wrote: >>> >>> Hi, >>> >>> Yesterday I checked how fast ceph-mds can process requests (a client >>> keeps sending getattr request of root inode). Requests rate I got is >>> only about half of same test I did a few weeks ago. Perf profile of >>> ceph-mds shows that messenger functions used more CPU time compared to >>> mimic code. Performance result and perf profiles are at >>> http://tracker.ceph.com/issues/36561. >>> >>> Regards >>> Yan, Zheng > -- Ricardo Dias Senior Software Engineer - Storage Team SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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