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Date: Sat, 14 May 2016 08:47:41 -0700 From: Roopa Prabhu <roopa@...ulusnetworks.com> To: Jiri Pirko <jiri@...nulli.us> CC: netdev@...r.kernel.org, davem@...emloft.net, nogahf@...lanox.com, idosch@...lanox.com, eladr@...lanox.com, yotamg@...lanox.com, ogerlitz@...lanox.com, nikolay@...ulusnetworks.com, linville@...driver.com, tgraf@...g.ch, gospo@...ulusnetworks.com, sfeldma@...il.com, sd@...asysnail.net, eranbe@...lanox.com, ast@...mgrid.com, edumazet@...gle.com, hannes@...essinduktion.org Subject: Re: [patch net-next 1/4] netdevice: add SW statistics ndo On 5/14/16, 5:49 AM, Jiri Pirko wrote: > Fri, May 13, 2016 at 08:47:48PM CEST, roopa@...ulusnetworks.com wrote: >> On 5/12/16, 11:03 PM, Jiri Pirko wrote: >>> Thu, May 12, 2016 at 11:10:08PM CEST, roopa@...ulusnetworks.com wrote: >>>> On 5/12/16, 4:48 AM, Jiri Pirko wrote: >>>>> From: Nogah Frankel <nogahf@...lanox.com> >>>>> >>>>> Till now we had a ndo statistics function that returned SW statistics. >>>>> We want to change the "basic" statistics to return HW statistics if >>>>> available. >>>>> In this case we need to expose a new ndo to return the SW statistics. >>>>> Add a new ndo declaration to get SW statistics >>>>> Add a function that gets SW statistics if a competible ndo exist >>>>> >>>>> Signed-off-by: Nogah Frankel <nogahf@...lanox.com> >>>>> Reviewed-by: Ido Schimmel <idosch@...lanox.com> >>>>> Signed-off-by: Jiri Pirko <jiri@...lanox.com> >>>>> --- >>>>> >>>> To me netdev stats is combined 'SW + HW' stats for that netdev. >>>> ndo_get_stats64 callback into the drivers does the magic of adding HW stats >>>> to SW (netdev) stats and returning (see enic_get_stats). HW stats is available for netdevs >>>> that are offloaded or are backed by hardware. SW stats is the stats that the driver maintains >>>> (logical or physical). HW stats is queried and added to the SW stats. >>> I'm not sure I follow. HW stats already contain SW stats. Because on >>> slow path every packet that is not offloaded and goes through kernel is >>> counted into HW stats as well (because it goes through HW port). >> yes, correct... we don't want to double count those. But since these stats are >> generally queried from hw, I am calling them HW stats. >> you will not really maintain a software counter for this. But, the driver can maintain its own >> counters for rx and tx errors etc and I call these SW stats. They are counted at the driver. >> >>> If you >>> do HW stats + SW stats, what you get makes no sense. Am I missing something? >> If you go by my definition of HW and SW stats above, on a ndo_get_stats64() call, >> you will add the SW counters + HW counters and return. In my definition, the pkts >> that was rx'ed or tx'ed successfully are always in the HW count. >> >>> Btw, looking at enic_get_stats, looks exactly what we introduce for >>> mlxsw in this patchset. >> In enic_get_stats, the ones counted in software are the ones taken from 'enic->' >> net_stats->rx_over_errors = enic->rq_truncated_pkts; >> net_stats->rx_crc_errors = enic->rq_bad_fcs; >> >>> With this patchset, we only allow user to se the actual stats for >>> slow-path aka SW stats. >> hmm...ok. But i am not sure how many will use this new attribute. >> When you do 'ip -s link show' you really want all counters on that port >> hardware or software does not matter at that point. >> >> My suggestion to move this to ethtool like attribute is because that is an existing >> way to break down your stats which ever way you want. And the best part is it can be >> customized (say rx_pkts_cpu_saw) > I bevieve that ethtool is really not a place to expose sw stats. Does > not make sense. 2 things: - i was surprised you don't want your ndo_get_stats64 to be a unified view of HW and SW stats - by bringing up ethtool like stats (IFLA_STATS_LINK_HW_EXTENDED) I am just saying it has always been a way to breakdown stats. If you don't want to show explicit SW stats there, there is always a way to show HW only stats....and now you know the delta between the unified stats and the HW only stats is your SW stats.
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