Messages in this thread | | | Date | Wed, 28 Oct 2020 16:36:42 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH v2 06/15] perf session: load data directory into tool process memory |
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On Tue, Oct 27, 2020 at 05:43:20PM +0300, Alexey Budankov wrote: > > On 27.10.2020 15:21, Jiri Olsa wrote: > > On Tue, Oct 27, 2020 at 10:37:58AM +0300, Alexey Budankov wrote: > >> > >> On 24.10.2020 18:43, Jiri Olsa wrote: > >>> On Wed, Oct 21, 2020 at 07:01:19PM +0300, Alexey Budankov wrote: > >>>> > >>>> Read trace files located in data directory into tool process memory. > >>>> Basic analysis support of data directories is provided for report > >>>> mode. Raw dump (-D) and aggregated reports are available for data > >>>> directories, still with no memory consumption optimizations. However > >>>> data directories collected with --compression-level option enabled > >>>> can be analyzed with little less memory because trace files are > >>>> unmaped from tool process memory after loading collected data. > >>>> The implementation is based on the prototype [1], [2]. > >>>> > >>>> [1] git clone https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git -b perf/record_threads > >>>> [2] https://lore.kernel.org/lkml/20180913125450.21342-1-jolsa@kernel.org/ > >>>> > >>>> Suggested-by: Jiri Olsa <jolsa@kernel.org> > >>> > >>> very loosely ;-) so there was a reason for all that reader refactoring, > >>> so we could have __perf_session__process_dir_events function: > >>> > >>> https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?h=perf/record_threads&id=308aa7cff1fed335401cfc02c7bac1a4644af68e > >> > >> Nonetheless. All that are necessary parts to make threaded data streaming > >> and analysis eventually merged into the mainline as joint Perf developers > >> community effort. > >> > >>> > >>> when reporting the threaded record data on really big servers, > >>> you will run out of memory, so you need to read and flush all > >>> the files together by smaller pieces > >> > >> Yes, handling all that _big_ data after collection to make it > >> helpful for analysis of performance issues is the other part > >> of this story so that possible OOM should be somehow avoided. > >> > >>> > >>> IMO we need to have this change before we allow threaded record > >> > >> There are use cases of perf tool as a data provider, btw VTune is not > >> the only one of them, and for those use cases threaded trace streaming > >> lets its users get to their data that the users just were loosing before. > >> This is huge difference and whole new level of support for such users. > >> Post-process scripting around perf (e.g. Python based) will benefit > >> from threaded trace streaming. Pipe mode can be extended to stream into > >> open and passed fds using threads (e.g. perf record -o -fd:13,14,15,16). > >> VTune-like tools can get performance data, load it into a (relational) > >> DB files and provide analysis. And all that uses perf tool at its core. > >> > >> I agree perf report OOM issue can exist on really-big servers but data > >> directories support for report mode for not-so-big servers and desktops > >> is already enabled with this smaller change. Also really-big-servers > >> come with really-big amount of memory and collection could possibly be > >> limited to only interesting phases of execution so the issue could likely > >> be avoided. At the same time threaded trace streaming could clarify on > >> real use cases that are blocked by perf report OOM issue and that would > >> clarify on exact required solution. So perf report OOM issue shouldn't > >> be the showstopper for upstream of threaded trace streaming. > > > > so the short answer is no, right? ;-) > > Answer to what question? Resolve OOM in perf report for data directories? > I don't see a simple solution for that. The next issue after OOM is resolved > is a very long processing of data directories. And again there is no simple > solution for that as well. But it still need progress in order to be resolved > eventually.
it's right here: https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?h=perf/record_threads&id=308aa7cff1fed335401cfc02c7bac1a4644af68e
jirka
> > > > > I understand all the excuses, but from my point of view we are > > adding another pain point (and there's already few ;-) ) that > > will make perf (even more) not user friendly > > I would not name it a paint point but instead a growth opportunity. > Now --threads can't be and is not enabled by default. When a user > asks --threads the tool can print warning in advance about lots of > data and possible perf report OOM limitation so confusion and > disappointment for users of perf report can be avoided in advance. > > > > > if we allow really friendly way to create huge data, we should > > do our best to be able to process it as best as we can > > It is just little to no more friendly as it is already now. > Everyone can grab patches apply and get threaded streaming. > Inclusion into mainline will standardize solution to build > and evolve upon and this is necessary step towards complete > support of data directories in perf tool suite. > > Alexei > > > > > jirka > > >
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