On Sun, 2013-04-28 at 16:09 +0200, Luca dariz wrote: > Il 28/04/2013 13:45, Luca dariz ha scritto: > > Il 26/04/2013 22:00, Luca dariz ha scritto: > >> Il 26/04/2013 16:35, Conor O'Gorman ha scritto: > >>> On Fri, 2013-04-26 at 14:13 +0200, Luca dariz wrote: > >>>> Use a tasklet to handle incoming packets. Fix #12917. > >>>> > >>>> Incoming packets are now processes in a tasklet instead of in the > >>>> irq handler; this should improve latency. > >>>> > >>>> This patch is based on a previous version of ltq-atm driver, which > >>>> did implement a tasklet. > >>>> > >>>> It has been tested on a arv4518pw with a > >>>> Lantiq Danube for about a month and it seems to work well. > >>> > >>> And how much 'better' is it? > >>> > >> > >> I did't measure latency with this patch and without it, so i can't tell > >> exactly. > >> > >> Luca > > > > A quick test with cyclictest > > (https://rt.wiki.kernel.org/index.php/Cyclictest): > > > > without the patch: > > > > cmdline: ./cyclictest -n > > # /dev/cpu_dma_latency set to 0us > > policy: other/other: loadavg: 0.51 0.33 0.27 1/43 3241 > > T: 0 ( 3241) P: 0 I:1000 C: 144288 Min: 40 Act: 93 Avg: 163 Max: 4456 > > > > with the patch: > > > > cmdline: ./cyclictest -n > > # /dev/cpu_dma_latency set to 0us > > policy: other/other: loadavg: 0.78 0.44 0.22 1/44 4981 > > T: 0 ( 3452) P: 0 I:1000 C: 82427 Min: 39 Act: 199 Avg: 252 Max: 18179 > > > > All latencies are measures in microseconds. > > > > Luca > > I forgot: during the test, a big download was in progress, to stress the > rx path a bit. >
Thank you for providing more information. I'll first say that I am not a gatekeeper on this code, but a user, so I try to review Lantiq specific changes and make hopefully relevant comments. As I understand the results, the average and maximum latency statistics have increased, with a small decrease to minimum? Looking at the system as a whole, it is a router whose primary function will be to move packets from the adsl (atm) interface to ethernet or pci-wifi. Given that under load the ethernet/wifi will most likely use napi interrupt moderation, the vast majority of interrupts firing will be the adsl/atm. Which latencies, therefore, are you concerned about? Ideally the adsl/atm driver on lantiq would use napi method, but I haven't investigated it's structure. I have looked at the bug report you reference, but feel you have side stepped the original problem with an alternative structure. Again, just my thoughts. Conor _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel
