[dpdk-dev] [PATCH v5] eal: use memzone to share tsc hz with secondary processes

Burakov, Anatoly anatoly.burakov at intel.com
Tue Aug 27 14:04:18 CEST 2019

On 26-Aug-19 2:44 PM, Jim Harris wrote:
> Ideally, get_tsc_freq_arch() is able to provide the
> TSC rate using arch-specific means.  When that is not
> possible, DPDK reverts to calculating the TSC rate with
> a 100ms nanosleep or 1s sleep.  The latter occurs more
> frequently in VMs which often do not have access to the
> data they need from arch-specific means (CPUID leaf 0x15
> or MSR 0xCE on x86).
> In secondary processes, the extra 100ms is especially
> noticeable and consumes the bulk of rte_eal_init()
> execution time.  To resolve this extra delay, have
> the primary process put the TSC rate into a shared
> memory region that the secondary process can lookup.
> Reduces rte_eal_init() execution time in a secondary
> process from 165ms to 66ms on my test system.
> Signed-off-by: Jim Harris <james.r.harris at intel.com>
> ---

I think this is a bad idea. If you're allocating something, you're 
supposed to free it in rte_eal_cleanup(). If you don't, that memory 
leaks (i.e. there are leftover hugepages after process exit). Since both 
primary and secondary are referencing it (even if only at init), there 
is no safe way to free this memzone.


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