On Tue, Apr 14, 2020 at 11:37 PM Mattias Rönnblom <[email protected]> wrote: > > On 2020-04-14 15:35, David Marchand wrote: > > On Tue, Apr 14, 2020 at 3:20 PM Mattias Rönnblom > > <[email protected]> wrote: > >> On 2020-04-14 06:43, Tonghao Zhang wrote: > >>> On Tue, Apr 14, 2020 at 12:07 PM Stephen Hemminger > >>> <[email protected]> wrote: > >>>> On Sun, 12 Apr 2020 16:27:53 +0800 > >>>> [email protected] wrote: > >>>> > >>>>> From: Tonghao Zhang <[email protected]> > >>>>> > >>>>> When rte_rand_init is invoked, and the kernel > >>>>> (kernel version < 3.17) running dpdk does't support > >>>>> *getentropy, at the same time, the cpu does't support > >>>>> rdseed, the rte_rand_init will invoke rte_get_timer_cycles > >>>>> which function will invoke rte_get_hpet_cycles > >>>>> (RTE_LIBEAL_USE_HPET was enabled) while *eal_hpet is not > >>>>> allocated. > >>>>> > >>>>> Fixes: faf8fd252785 ("eal: improve entropy for initial PRNG seed") > >>>>> Fixes: 3f002f069612 ("eal: replace libc-based random generation with > >>>>> LFSR") > >>>>> > >>>>> Cc: [email protected] > >>>>> > >>>>> Signed-off-by: Tonghao Zhang <[email protected]> > >>>> Are you sure this patch won't change current default to use HPET (which > >>>> is slower)? > >>> In rte_eal_timer_init (linux/eal_timer.c)， it will set > >>> eal_timer_source = EAL_TIMER_TSC too. > >>> So after rte_eal_init, eal_timer_source == EAL_TIMER_TSC which is the > >>> default timer source actually. > >>> Then this patch will affect RTE_INIT function which invoke > >>> rte_get_timer_cycles. but hpet is not available yet. > >> > >> Would using rte_rdtsc() directly be an option? > > s/rte_rdtsc/rte_get_tsc_cycles/ > > > > This could work, but I am a bit surprised to see an initialisation in > > a constructor. > > The commitlog that moved rte_srand() from rte_eal_init does not > > explain why it was moved. > > > > > The initialization (i.e. automatic seeding) grew in complexity somewhat, > and with the new rte_random.c file, it felt like it would have a good, > new home. > > > That said, maybe it would have been better to add an initialization > function to the rte_random.h API, and have it called from > rte_eal_init(), to avoid the ordering issues with constructors. If we use that solution we can register a callback which invoked when almost resources are available: http://patches.dpdk.org/patch/68313/ > Yet > another alternative would be to just move the seeding logic. > >
-- Best regards, Tonghao
