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

[Bruce Richardson]

On Mon, Aug 26, 2019 at 06:44:46AM -0700, 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 using shared memory is a lot simpler to manage, so LGTM.

Acked-by: Bruce Richardson <bruce.richardson at intel.com>