Re: [PATCH] app/testpmd: improve sse based macswap

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Jul 23, 2024 at 05:45:57PM +0100, Ferruh Yigit wrote:
> On 7/16/2024 7:37 AM, Vipin Varghese wrote:
> > Goal of the patch is to improve SSE macswap on x86_64 by reducing
> > the stalls in backend engine. Original implementation of the SSE
> > macswap makes loop call to multiple load, shuffle & store. Using
> > SIMD ISA interleaving we can reduce the stalls for
> >  - load SSE token exhaustion
> >  - Shuffle and Load dependency
> > 
> > Also other changes which improves packet per second are
> >  - Filling access to MBUF for offload flags which is separate cacheline,
> >  - using register keyword
> > 
> > Build test using meson script:
> > ``````````````````````````````
> > 
> > build-gcc-static
> > buildtools
> > build-gcc-shared
> > build-mini
> > build-clang-static
> > build-clang-shared
> > build-x86-generic
> > 
> > Test Results:
> > `````````````
> > 
> > Platform-1: AMD EPYC SIENA 8594P @2.3GHz, no boost
> > 
> > ------------------------------------------------
> > TEST IO 64B: baseline <NIC : MPPs>
> >  - mellanox CX-7 2*200Gbps : 42.0
> >  - intel E810 1*100Gbps : 82.0
> >  - intel E810 2*200Gbps (2CQ-DA2): 82.45
> > ------------------------------------------------
> > TEST MACSWAP 64B: <NIC : Before : After>
> >  - mellanox CX-7 2*200Gbps : 31.533 : 31.90
> >  - intel E810 1*100Gbps : 50.380 : 47.0
> >  - intel E810 2*200Gbps (2CQ-DA2): 48.840 : 49.827
> > ------------------------------------------------
> > TEST MACSWAP 128B: <NIC : Before: After>
> >  - mellanox CX-7 2*200Gbps: 30.946 : 31.770
> >  - intel E810 1*100Gbps: 49.386 : 46.366
> >  - intel E810 2*200Gbps (2CQ-DA2): 47.979 : 49.503
> > ------------------------------------------------
> > TEST MACSWAP 256B: <NIC: Before: After>
> >  - mellanox CX-7 2*200Gbps: 32.480 : 33.150
> >  - intel E810 1 * 100Gbps: 45.29 : 44.571
> >  - intel E810 2 * 200Gbps (2CQ-DA2): 45.033 : 45.117
> > ------------------------------------------------
> > 
> > Platform-2: AMD EPYC 9554 @3.1GHz, no boost
> > 
> > ------------------------------------------------
> > TEST IO 64B: baseline <NIC : MPPs>
> >  - intel E810 2*200Gbps (2CQ-DA2): 82.49
> > ------------------------------------------------
> > <NIC intel E810 2*200Gbps (2CQ-DA2): Before : After>
> > TEST MACSWAP: 1Q 1C1T
> >  64B: : 45.0 : 45.54
> > 128B: : 44.48 : 44.43
> > 256B: : 42.0 : 41.99
> > +++++++++++++++++++++++++
> > TEST MACSWAP: 2Q 2C2T
> >  64B: : 59.5 : 60.55
> > 128B: : 56.78 : 58.1
> > 256B: : 41.85 : 41.99
> > ------------------------------------------------
> > 
> > Signed-off-by: Vipin Varghese <vipin.varghese@amd.com>
> >
> 
> Hi Bruce, John,
> 
> Can you please help testing macswap performance with this patch on Intel
> platforms, to be sure it is not causing regression?
> 
Hi Ferruh,

We can try and get some Intel numbers for you, but I think at this point it
is better deferred to 24.11 due to lack of discussion and analysis of the
numbers. This is because the numbers above already show that it is causing
regressions - in fact many of the regressions are larger than the benefits
shown. This may be acceptable, but it would imply that we shouldn't be too
hasty in applying the patch.

Regards,
/Bruce