Hi Stephen, Sorry about the delay in responding to your comment.
Maybe I'm missing something but I don't consider 64-bit counter rollover to be a problem. The DPDK QoS stats are just 32-bits wide and are zeroed when read. So if we read them frequently enough the 32-bit counters won't wrap. This new API is just a convenient way to read the 32-bit counters into variables that are 64-bit wide which allows Vyatta to have a common API slightly above the DPDK. I'd hope that at some point in time the DPDK will move to 64-bit counters, but there may be technical reasons why this can't happen that I'm not aware of (support for 32-bit CPUs??) Regards Alan On Mon, Jul 23, 2018 at 5:52 PM, Stephen Hemminger <step...@networkplumber.org> wrote: > On Wed, 18 Jul 2018 15:51:39 +0100 > alangordonde...@gmail.com wrote: > >> From: Alan Dewar <alan.de...@att.com> >> >> Add new APIs to retrieve counters in 64-bit wide fields. >> >> Signed-off-by: Alan Dewar <alan.de...@att.com> > > Do you want to consider 64 bit counter roll over on 32 bit platform? > The problem is that incrementing an 64 bit value is not atomic on > 32 bit cpu. The carry operation can race with reading. > > The kernel has special case code to do restartable sequence for > accessing 64 bit counter on 32 bit CPU. These functions become > nop's on 64bit.
