On Thu, Mar 12, 2015 at 3:34 PM, David Ahern <[email protected]> wrote: > On 3/12/15 1:23 PM, Stephane Eranian wrote: >>> >>> Rounds and flushing after them helps with the user experience -- at least >>> for some commands. On systems with 1024 cpus perf data files get large >>> quickly and the resulting analysis command can appear to hang for long >>> periods (e.g., i have done 1 second data collections that generate 5GB >>> files >>> and take 30-45 minutes before perf shows any output). >>> >>> I have a patch to perf-record to allow a user to specify the poll >>> timeout. >>> That helps define the maximum time between 'rounds' on the record side >>> and >>> then commands that show each event (e.g, perf script) will show output >>> much >>> more quickly without the need to consume large amounts of memory or >>> process >>> the entire file before displaying events. >>> >> I can understand this but not at the cost of correctness. You have no >> guarantee >> that events will appear in the perf.data with a fixed maximum time window, >> i.e., >> beyond the window, out-of-order events may be discarded. >> There ought to be a better way of keeping the user aware of what's going >> on >> with the progress bar. > > > Theoretically there are no events coming in out of order. Have you seen the > comment before process_finished_round() in util/session.c? > > In practice it did happen occasionally and perf would dump: > Warning: Timestamp below last timeslice flush > > and then terminate. That was removed recently by Jiri I think and events out > of the window are discarded (??). > > In my case I don't want a progress bar, I want output and I don't need the > entire file processed for output to start. For a while I was dropping back > to the ftrace interface in debugfs b/c it was faster. > > For the JIT case you tried appending events at the end of the file but that > makes them no where near the real time points so what you really need is to > insert events into the stream. Perhaps the separate files option would help > -- jit events in a separate file and inserted based on time as the files are > processed? > That's how I had it initially but it mean you have to use perf inject or have perf record inject at the end, i.e., two passes over the perf.data file. I can certainly have this in perf inject.
What the point of having all the ordered event logic if you are saying events must be saved in order. I don't think there is a way to make that guarantee when monitoring multiple CPUs at the same time. >From you description it seems to me, you script wants to process data quickly. Is this an interactive tool? If not, you need to go through all the samples anyway. > David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
