On 3/3/2023 2:16 AM, Long Li wrote: >> Subject: Re: [PATCH] net/mana: use RTE_LOG_DP for logs on datapath >> >> On Thu, 23 Feb 2023 10:09:17 -0800 >> Stephen Hemminger <step...@networkplumber.org> wrote: >> >>> On Thu, 23 Feb 2023 14:07:25 +0000 >>> Ferruh Yigit <ferruh.yi...@amd.com> wrote: >>> >>>> Overall I am not sure if anyone is interested in driver datapath >>>> logs other than driver developers themselves. >>>> >>>> For datapath logging I think there are two concerns, >>>> 1) It should not eat *any* cycles unless explicitly enabled >>>> 2) Capability of enable/disable them because of massive amount of >>>> log it can generate >>>> >>>> >>>> Currently there are two existing approaches for driver datapath logging: >>>> i) Controlled by 'RTE_ETHDEV_DEBUG_RX/TX' compile time flag, >>>> when enabled 'rte_log()' is used with Rx/Tx specific log type. >>>> ii) 'RTE_LOG_DP' ', compile time control per logtype via >>>> 'RTE_LOG_DP_LEVEL', >>>> when enabled 'rte_log()' is used with PMD logtype. >>>> >>>> >>>> In (ii), need to re-compile code when you need to increase the log >>>> verbosity, and it leaks to production code as mentioned above. >>>> >>>> For (i), developer compiles once enabling debug, later can fine >>>> grain log level dynamically. This is more DPDK developer focused approach. >>>> >>>> >>>> [1] >>>> According above, what do you think to retire 'RTE_LOG_DP', (at least >>>> within ethdev datapath), and chose (i) as preferred datapath logging? >>> >>> I agree, the current tx/rx logging is a mess. >>> Each driver is different, each driver has to have something to enable >>> it; and it really isn't useful beyond the driver developer. >>> >>> Using tracing seems like a much better option. Could we agree on a >>> common set of trace points for drivers and fix all drivers to use the same >> thing. >>> Probably will cause some upset among driver developers: >>> "where did my nice printf's go, now I have to learn tracing" >>> but DPDK has a good facility here, lets use it. >>> >>> My proposal would be: >>> - agree on common set of trace points >>> - apply to all drivers >>> - remove RTE_LOG_DP() >>> - remove per driver RX/TX options >>> - side effect, more uses of RTE_LOGTYPE_PMD go away. >> >> Here is an example of using tracepoints instead. >> Compile tested for example only. >> >> Note: using tracepoints it is possible to keep some of the tracepoints even >> if >> fastpath is not enabled. Things like running out of Tx or Mbuf is not >> something >> that is perf critical; but would be good for application to see. > > Thank you for the example. > > I sent another patch converting data path logs (mana) to trace points. >
Hi Long, Thanks for the effort, you were quick on this while discussion is going on. Although tracepoint is a good feature, I am not sure if it can fully replace the logging. I think usage is slightly different, trace is missing custom human readable message, which can be very helpful for end user. And overall, it is a high level decision to switch logging to trace, it is inconsistent to switch only single driver, perhaps techboard (cc'ed) can discuss this. Until such consensus reached, I think driver should continue with logging. And for the logging, I suggest option (i) above, I was hoping more comments but since it is missing I hope this can be discussed in techboard for a conclusion.
