[Babel-users] [PATCH] Fix ifup bug in send_multicast

[Dave Taht]

My followup just created a FOR_ALL_INTERFACES_UP macro which led to
even less code. :)

Elsewhere I've been dithering. The proof of concept for uthash in
resend, was quite satisfying but far too much unneeded overhead (56
bytes per entry on 64 bits!! + the malloc overhead!), so I have been
looking over khash and so forth (
https://github.com/attractivechaos/klib )

the benchmarks were impressive, but like all benchmarks, flawed -
testing an integer hash, where we need 34 bytes of "some hash"
(jenkins? spooky?), and x86 only, where I care mostly about mips, and
I care about startup time for a hash a lot....- I figure reworking
those benchmarks to (say) import a BGP route table, and then try to
project how much SADR and p2p routes are used, and a real
lookup/insert ratio in a benchmark would be more useful. But I get
14MOPs/sec on the basic benchmark on my x86 box on a million
integers... lookups take 10ns....

Babel has an ordered "slot" concept in it...

Elsewhere I was poking into the the evolution of the kernel's
timerwheel thing ( https://lwn.net/Articles/646950/ ) which makes the
valid point that most babel "timeouts" are really recurring events....

And elsewhere, elsewhere, figured out how to switch to 64bit time.

In glibc (not musl so far as I know) the clock_getttime lookup is
incredibly fast because it just maps in the relevant kernel page and
does the work without a syscall, and dealing with a straight 64 bit
quantity would always be a win on 64 bit platforms and probably a win
even on 32 bit ones.

#if __APPLE__
#include <mach/mach_time.h>
static mach_timebase_info_data_t timebase;
#endif


static s64
monotime(void) {
#if __APPLE__
        unsigned long long abt;

        abt = mach_absolute_time();
        abt = abt * timebase.numer / timebase.denom;

        return abt / 1000LL;
#else
        struct timespec ts;

        clock_gettime(CLOCK_MONOTONIC, &ts);

        return (ts.tv_sec * 1000000L) + (ts.tv_nsec / 1000L);
#endif
} /* monotime() */