Hi, On 2017-09-21 05:34 AM, liguang li wrote: > Hi, > > On Wed, Sep 20, 2017 at 10:58 PM, Jonathan Rajotte Julien > wrote: > > Hi, > > On 2017-09-20 05:12 AM, liguang li wrote: > > > > > > On Tue, Sep 19, 2017 at 10:57 PM, Jonathan Rajotte-Julien >> wrote: > > > >     On Tue, Sep 19, 2017 at 03:53:27PM +0800, liguang li wrote: > >     >    Hi, > >     >    On Mon, Sep 18, 2017 at 11:18 PM, Jonathan Rajotte-Julien > >     >    <[1]jonathan.rajotte-julien at efficios.com >> wrote: > >     > > >     >      Hi, > >     >      On Mon, Sep 18, 2017 at 11:32:07AM +0800, liguang li wrote: > >     >      >    Hi, > >     >      > > >     >      >    Create a session in live-reading mode, run a application which > >     >      having very > >     >      >    high event throughput, then prints > >     >      >    the events with babeltrace. We found the live trace viewer are > >     >      viewing > >     >      >    events a few seconds ago, and as time > >     > > >     >      Could you provide us the version used for babeltrace, lttng-tools and > >     >      lttng-ust? > >     > > >     >     Babeltrace: 1.5.1 > > > >     Update to babeltrace 1.5.3. > > > >     >     Lttng-tools: 2.8.6 > > > >     Update to lttng-tools 2.8.8 > > > >     >     Lttng-ust: 2.8.2 > >     > > >     >      >    goes on, the delay will be bigger and bigger. > >     > > >     >      A similar issues was observed a couple months ago, which implicated > >     >      multiple delayed ack > >     >      problems during communication between lttng-relayd and babeltrace. > >     > > >     >      The following fixes were merged: > >     > > >     >      [1] > >     >      [2]https://github.com/lttng/lttng-tools/commit/b6025e9476332b75eb8184345c3eb3e924780088 > > >     >      [2] > >     >      [3]https://github.com/efficios/babeltrace/commit/de417d04317ca3bc30f59685a9d19de670e4b11d > > >     >      [3] > >     >      [4]https://github.com/efficios/babeltrace/commit/4594dbd8f7c2af2446a3e310bee74ba4a2e9d648 > > >     > > >     >      In the event that you are already using an updated version of babeltrace > >     >      and > >     >      lttng-tools, it would be pertinent to provide us with a simple > >     >      reproducer so we > >     >      can assess the issue. > > > >     The version you are using does not include the mentioned fixes. Please update > >     and redo your experiment. > > > > > > Test this issue in the version you have listed, the issue still exists. > > Given that previous versions had a major timing problem there I would expect to have some improvement. > > In that case, we will need a lot more information on your benchmarking strategy. > We will need a simple reproducer, your benchmark code (r,gnuplot etc.), your overall methodology > to be able to reproduce the issue locally. Otherwise, it will be very hard > to come to any conclusion. > > > Sorry, we can not provide the detailed information about the benchmark code due to the company regulations. >   > > >   > > > >     Cheers > > > >     > > >     >      > >     >     Steps: > >     >     lttng create session --live -U net://* > >     >     lttng enable-channel -s session -u ch1 > >     >     lttng enable-event -s session -c ch1 -u -a > >     >     lttng start > >     >      > >     >     Run a high event throughput application, which is multithreaded > >     >    application> > > > > In the multithreaded application, each tracepoint will have the wall > > time of the system,then we can easily reproduce this issue through > > comparing the time of recorded event and the system wall time. > >   > > > >     >     babeltrace -i lttng-live net://* > >     >      > >     >     After a while, we found the timestamp of the event in the babeltrace is > >     >    different with the time in host > >     >     which run the application. And the delay will be bigger and bigger with > >     >    time goes. > >     >      > >     > > >     >      Cheers > >     >      >    I checked the source code, found Babeltrace in live-reading mode > >     >      will read > >     >      >    the recorded events in the CTF > >     >      >    files, and then parse and print it in a single thread. The process > >     >      is a > >     >      >    little slow, do you have any ideas to > >     >      >    improve the process. > > > > > > From my understanding of the source code, the process of parse and > > print event will consume a lot of time. For example, the multithreaded > > application will consume 3 CPUs, in a specified time,3 subbuffers will > > be filled and sent to lttng-relayd daemon, recorded into the CTF files. > > If in the specified time, babeltrace only handled 2 subbuffers' event, > > thenthe issue will happens. > > Did you perform a bisection for where the delay come from? Reception of packet? formatting of event? ? > What is the throughput of the application? ? This is a key element if anyone want to test at home. It can be expressed in event/s, event/ms. > How many tracepoint definition> Does babeltrace catch up if a quiescent period is given? > > > I think so. >   > > Could you provide us with statistics, timing data, etc.? > > What type of delay are we talking about? > > > For example, the system wall time is 5:18 PM now, but the Babeltrace is still printing events which > have time 5:10 PM. Then stop running the application, the Babeltrace still need some times to print > the recorded events. > > I think the root cause is that the parsing and printing process is a bit slow. So i want to know if there > are any method to improve the performance of this process. A simple experiment would be to run a bounded workload to perform a quick timing evaluation of babeltrace with a streamed trace (on disk) and in live mode. Calculate the time (time babeltrace path_to_streamed_trace) it takes babeltrace to read the on disk trace and perform the same experiment with a live trace. It is important to bound your experiment and have mostly the same workload in both experiment. This will give us a rough estimate of the disparity between both scenario. Cheers