Re: [dpdk-dev] Reshuffling of rte_mbuf structure.

[Arnon Warshavsky <arnon@qwilt.com>]

My 2 cents,

This was brought up in the recent user space summit, and it seems that
indeed there is no one cache lines arrangement that fits all.
OTOH multiple compile time options to suffice all flavors, would make it
unpleasant to read maintain test and debug.
(I think there was quiet a consensus in favor of reducing compile options
in general)

Currently I manage similar deviations via our own source control which I
admit to be quite a pain.
I would prefer an option of code manipulation/generation by some script
during dpdk install,
which takes the default version of rte_mbuf.h,
along with an optional user file (json,xml,elvish,whatever) defining the
structure replacements,
creating your custom version, and placing it instead of the installed copy
of rte_mbuf.h.
Maybe the only facility required from dpdk is just the ability to register
calls to such user scripts at some install stage(s), providing the mean
along with responsibility to the user.

/Arnon



On Sat, Oct 31, 2015 at 6:44 AM, shesha Sreenivasamurthy (shesha) <
shesha@cisco.com> wrote:

> In Cisco, we are using DPDK for a very high speed packet processor
> application. We don't use NIC TCP offload / RSS hashing. Putting those
> fields in the first cache-line - and the obligatory mb->next datum in the
> second cache line - causes significant LSU pressure and performance
> degradation. If it does not affect other applications, I would like to
> propose reshuffling of fields so that the obligator "next" field falls in
> first cache line and RSS hashing goes to next. If this re-shuffling indeed
> hurts other applications, another idea is to make it compile time
> configurable. Please provide feedback.
>
> --
> - Thanks
> char * (*shesha) (uint64_t cache, uint8_t F00D)
> { return 0x0000C0DE; }
>



-- 

*Arnon Warshavsky*
*Qwilt | work: +972-72-2221634 | mobile: +972-50-8583058 | arnon@qwilt.com
<arnon@qwilt.com>*