> On Aug 26, 2020, at 11:41 AM, Bruce Richardson <bruce.richard...@intel.com> > wrote: > > On Wed, Aug 26, 2020 at 05:33:20PM +0100, Ferruh Yigit wrote: >> On 7/14/2020 10:51 PM, Dharmik Thakkar wrote: >>> Meson build system lacks support for >>> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and >>> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS configuration options. >>> >>> One solution is to add these options within meson_options.txt >>> >>> Since adding these as runtime config causes no performance impact, >> >> Hi Dharmik, >> >> These are on the datapath, and even disable there will be additional >> checks, isn't it expected to have some impact? Did you do any >> measurements for it?
Hi Ferruh, In my measurements, I saw a maximum performance degradation of 0.3% for rx and tx throughput (pps) with runtime option (both disabled and enabled cases) when compared to compile time option.. There was no difference in cycles per packet measurement. I did these measurements with Mellanox-ConnectX-5 card on N1SDP server with ’set fwd mac retry’ option. >> > Branches that always predict the same way can be very cheap, and unless > proven to be a problem, I'd see no issue with having a few on the datapath > - especially if it just one or two per burst. If we start seeing a > significant number, or ones that occur for every packet, then we perhaps > need to be more cautious. > > I also think that using lots of different CFLAGS for turning things on and > off is as bad - or even worse - than using the old build-time config > options, just this time we don't have a single list of them somewhere! > Therefore, I think we really need to start converting these to runtime > options where we can. > > Regards, > /Bruce
