On Fri, Aug 26, 2022 at 12:35:16PM +0530, Jerin Jacob wrote: > On Thu, Aug 25, 2022 at 8:56 PM Kevin Laatz <kevin.la...@intel.com> wrote: > > > > From: Anatoly Burakov <anatoly.bura...@intel.com> > > > > Currently, there is no way to measure lcore poll busyness in a passive way, > > without any modifications to the application. This patch adds a new EAL API > > that will be able to passively track core polling busyness. > > > > The poll busyness is calculated by relying on the fact that most DPDK API's > > will poll for packets. Empty polls can be counted as "idle", while > > non-empty polls can be counted as busy. To measure lcore poll busyness, we > > simply call the telemetry timestamping function with the number of polls a > > particular code section has processed, and count the number of cycles we've > > spent processing empty bursts. The more empty bursts we encounter, the less > > cycles we spend in "busy" state, and the less core poll busyness will be > > reported. > > > > In order for all of the above to work without modifications to the > > application, the library code needs to be instrumented with calls to the > > lcore telemetry busyness timestamping function. The following parts of DPDK > > are instrumented with lcore telemetry calls: > > > > - All major driver API's: > > - ethdev > > - cryptodev > > - compressdev > > - regexdev > > - bbdev > > - rawdev > > - eventdev > > - dmadev > > - Some additional libraries: > > - ring > > - distributor > > > > To avoid performance impact from having lcore telemetry support, a global > > variable is exported by EAL, and a call to timestamping function is wrapped > > into a macro, so that whenever telemetry is disabled, it only takes one > > additional branch and no function calls are performed. It is also possible > > to disable it at compile time by commenting out RTE_LCORE_BUSYNESS from > > build config. > > > > This patch also adds a telemetry endpoint to report lcore poll busyness, as > > well as telemetry endpoints to enable/disable lcore telemetry. A > > documentation entry has been added to the howto guides to explain the usage > > of the new telemetry endpoints and API. > > > > Signed-off-by: Kevin Laatz <kevin.la...@intel.com> > > Signed-off-by: Conor Walsh <conor.wa...@intel.com> > > Signed-off-by: David Hunt <david.h...@intel.com> > > Signed-off-by: Anatoly Burakov <anatoly.bura...@intel.com> > > > > --- > > v3: > > * Fix missed renaming to poll busyness > > * Fix clang compilation > > * Fix arm compilation > > > > v2: > > * Use rte_get_tsc_hz() to adjust the telemetry period > > * Rename to reflect polling busyness vs general busyness > > * Fix segfault when calling telemetry timestamp from an unregistered > > non-EAL thread. > > * Minor cleanup > > --- > > > diff --git a/meson_options.txt b/meson_options.txt > > index 7c220ad68d..725b851f69 100644 > > --- a/meson_options.txt > > +++ b/meson_options.txt > > @@ -20,6 +20,8 @@ option('enable_driver_sdk', type: 'boolean', value: > > false, description: > > 'Install headers to build drivers.') > > option('enable_kmods', type: 'boolean', value: false, description: > > 'build kernel modules') > > +option('enable_lcore_poll_busyness', type: 'boolean', value: true, > > description: > > + 'enable collection of lcore poll busyness telemetry') > > IMO, All fastpath features should be opt-in. i.e default should be false. > For the trace fastpath related changes, We have done the similar thing > even though it cost additional one cycle for disabled trace points >
We do need to consider runtime and build defaults differently, though. Since this has also runtime enabling, I think having build-time enabling true as default is ok, so long as the runtime enabling is false (assuming no noticable overhead when the feature is disabled.) /Bruce