> From: Bruce Richardson [mailto:bruce.richard...@intel.com]
> Sent: Friday, 7 January 2022 12.16
> 
> On Sat, Dec 25, 2021 at 01:16:03AM +0100, Morten Brørup wrote:
> > > From: Dharmik Thakkar [mailto:dharmik.thak...@arm.com] Sent:
> Friday, 24
> > > December 2021 23.59
> > >
> > > Current mempool per core cache implementation stores pointers to
> mbufs
> > > On 64b architectures, each pointer consumes 8B This patch replaces
> it
> > > with index-based implementation, where in each buffer is addressed
> by
> > > (pool base address + index) It reduces the amount of memory/cache
> > > required for per core cache
> > >
> > > L3Fwd performance testing reveals minor improvements in the cache
> > > performance (L1 and L2 misses reduced by 0.60%) with no change in
> > > throughput
> > >
> > > Micro-benchmarking the patch using mempool_perf_test shows
> significant
> > > improvement with majority of the test cases
> > >
> > > Number of cores = 1: n_get_bulk=1 n_put_bulk=1 n_keep=32
> > > %_change_with_patch=18.01 n_get_bulk=1 n_put_bulk=1 n_keep=128
> > > %_change_with_patch=19.91 n_get_bulk=1 n_put_bulk=4 n_keep=32
> > > %_change_with_patch=-20.37 (regression) n_get_bulk=1 n_put_bulk=4
> > > n_keep=128 %_change_with_patch=-17.01 (regression) n_get_bulk=1
> > > n_put_bulk=32 n_keep=32 %_change_with_patch=-25.06 (regression)
> > > n_get_bulk=1 n_put_bulk=32 n_keep=128 %_change_with_patch=-23.81
> > > (regression) n_get_bulk=4 n_put_bulk=1 n_keep=32
> > > %_change_with_patch=53.93 n_get_bulk=4 n_put_bulk=1 n_keep=128
> > > %_change_with_patch=60.90 n_get_bulk=4 n_put_bulk=4 n_keep=32
> > > %_change_with_patch=1.64 n_get_bulk=4 n_put_bulk=4 n_keep=128
> > > %_change_with_patch=8.76 n_get_bulk=4 n_put_bulk=32 n_keep=32
> > > %_change_with_patch=-4.71 (regression) n_get_bulk=4 n_put_bulk=32
> > > n_keep=128 %_change_with_patch=-3.19 (regression) n_get_bulk=32
> > > n_put_bulk=1 n_keep=32 %_change_with_patch=65.63 n_get_bulk=32
> > > n_put_bulk=1 n_keep=128 %_change_with_patch=75.19 n_get_bulk=32
> > > n_put_bulk=4 n_keep=32 %_change_with_patch=11.75 n_get_bulk=32
> > > n_put_bulk=4 n_keep=128 %_change_with_patch=15.52 n_get_bulk=32
> > > n_put_bulk=32 n_keep=32 %_change_with_patch=13.45 n_get_bulk=32
> > > n_put_bulk=32 n_keep=128 %_change_with_patch=11.58
> > >
> > > Number of core = 2: n_get_bulk=1 n_put_bulk=1 n_keep=32
> > > %_change_with_patch=18.21 n_get_bulk=1 n_put_bulk=1 n_keep=128
> > > %_change_with_patch=21.89 n_get_bulk=1 n_put_bulk=4 n_keep=32
> > > %_change_with_patch=-21.21 (regression) n_get_bulk=1 n_put_bulk=4
> > > n_keep=128 %_change_with_patch=-17.05 (regression) n_get_bulk=1
> > > n_put_bulk=32 n_keep=32 %_change_with_patch=-26.09 (regression)
> > > n_get_bulk=1 n_put_bulk=32 n_keep=128 %_change_with_patch=-23.49
> > > (regression) n_get_bulk=4 n_put_bulk=1 n_keep=32
> > > %_change_with_patch=56.28 n_get_bulk=4 n_put_bulk=1 n_keep=128
> > > %_change_with_patch=67.69 n_get_bulk=4 n_put_bulk=4 n_keep=32
> > > %_change_with_patch=1.45 n_get_bulk=4 n_put_bulk=4 n_keep=128
> > > %_change_with_patch=8.84 n_get_bulk=4 n_put_bulk=32 n_keep=32
> > > %_change_with_patch=-5.27 (regression) n_get_bulk=4 n_put_bulk=32
> > > n_keep=128 %_change_with_patch=-3.09 (regression) n_get_bulk=32
> > > n_put_bulk=1 n_keep=32 %_change_with_patch=76.11 n_get_bulk=32
> > > n_put_bulk=1 n_keep=128 %_change_with_patch=86.06 n_get_bulk=32
> > > n_put_bulk=4 n_keep=32 %_change_with_patch=11.86 n_get_bulk=32
> > > n_put_bulk=4 n_keep=128 %_change_with_patch=16.55 n_get_bulk=32
> > > n_put_bulk=32 n_keep=32 %_change_with_patch=13.01 n_get_bulk=32
> > > n_put_bulk=32 n_keep=128 %_change_with_patch=11.51
> > >
> > >
> > > From analyzing the results, it is clear that for n_get_bulk and
> > > n_put_bulk sizes of 32 there is no performance regression IMO, the
> > > other sizes are not practical from performance perspective and the
> > > regression in those cases can be safely ignored
> > >
> > > Dharmik Thakkar (1): mempool: implement index-based per core cache
> > >
> > >  lib/mempool/rte_mempool.h             | 114
> +++++++++++++++++++++++++-
> > >  lib/mempool/rte_mempool_ops_default.c |   7 ++ 2 files changed,
> 119
> > >  insertions(+), 2 deletions(-)
> > >
> > > -- 2.25.1
> > >
> >
> > I still think this is very interesting. And your performance numbers
> are
> > looking good.
> >
> > However, it limits the size of a mempool to 4 GB. As previously
> > discussed, the max mempool size can be increased by multiplying the
> index
> > with a constant.
> >
> > I would suggest using sizeof(uintptr_t) as the constant multiplier,
> so
> > the mempool can hold objects of any size divisible by
> sizeof(uintptr_t).
> > And it would be silly to use a mempool to hold objects smaller than
> > sizeof(uintptr_t).
> >
> > How does the performance look if you multiply the index by
> > sizeof(uintptr_t)?
> >
> 
> Each mempool entry is cache aligned, so we can use that if we want a
> bigger
> multiplier.

Thanks for chiming in, Bruce.

Please also read this discussion about the multiplier:
http://inbox.dpdk.org/dev/calbae1prqyyog96f6ecew1vpf3toh1h7mzzuliy95z9xjbr...@mail.gmail.com/

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