On Fri 2016-02-26 14:22:42, Kazimierz Krosman wrote: > On 02/25/2016 10:47 PM, Tejun Heo wrote: > >I'm not sure this is the right layer to implement generic logging > >facility. > In general this patches add only one feature- possibility of adding > and deleting > new kmsg devices, so I think that it can be treated as kmsg upgrade. > >>2. Using kmsg can cause lower CPU utilisation in the real-word use case than > >>>userspace logging mechanisms. > >>>We created 2 tests: (1) 100 writer processes write to created kmsg buffer and > >>>(2) 100 writers write to socket (stream)- there is one reader to protect > >>>socket buffer against overflow. Tests show that cpu utilisation in case of first > >>>test is about 2.3 times lower (39.1%) than it is in second case (87.7%) (measured > >>>with top program; tests code is attached below). Tested on Odroid XU4. > >This sounds like a generic IPC problem than anything else. > > For the test purpose I've written two tests (attached in cover > letter). I think that tests > show that in this use case (multiple writers) system with additional > kmsg devices > consumes less CPU time than system which use sockets for logging. > Logging system > based on sockets needs read process, that continuously reads socket > and protects > against socket buffers overflow and messages drop. It is one of > advantages of this > solution: no maintenance. Wait. The net addition of this patch set is 1755 lines out of it 526 lines seems to be in non-test code. You added another level of complexity into the handling of the ring buffer(s). And it will require no maintenance? > Could you explain in more detail what did you mean by IPC problems? I guess that the idea was to make IPC more effective in general. You definitely could not move all functionality that needs IPC into the kernel. Best Regards, Petr -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
