On Fri, May 17, 2019 at 2:23 PM Maxime Coquelin <maxime.coque...@redhat.com> wrote:
> Some OVS-DPDK PVP benchmarks show a performance drop > when switching from DPDK v17.11 to v18.11. > > With the addition of packed ring layout support, > rte_vhost_enqueue_burst and rte_vhost_dequeue_burst > became very large, and only a part of the instructions > are executed (either packed or split ring used). > > This series aims at improving the I-cache pressure, > first by un-inlining split and packed rings, but > also by moving parts considered as cold in dedicated > functions (dirty page logging, fragmented descriptors > buffer management added for CVE-2018-1059). > > With the series applied, size of the enqueue and > dequeue split paths is reduced significantly: > > +---------+--------------------+---------------------+ > | Version | Enqueue split path | Dequeue split path | > +---------+--------------------+---------------------+ > | v19.05 | 16461B | 25521B | > | +series | 7286B | 11285B | > +---------+--------------------+---------------------+ > > Using perf tool to monitor iTLB-load-misses event > while doing PVP benchmark with testpmd as vswitch, > we can see the number of iTLB misses being reduced: > > - v19.05: > # perf stat --repeat 10 -C 2,3 -e iTLB-load-miss -- sleep 10 > > Performance counter stats for 'CPU(s) 2,3' (10 runs): > > 2,438 iTLB-load-miss > ( +- 13.43% ) > > 10.00058928 +- 0.00000336 seconds time elapsed ( +- 0.00% ) > > - +series: > # perf stat --repeat 10 -C 2,3 -e iTLB-load-miss -- sleep 10 > > Performance counter stats for 'CPU(s) 2,3' (10 runs): > > 55 iTLB-load-miss > ( +- 10.08% ) > > 10.00059466 +- 0.00000283 seconds time elapsed ( +- 0.00% ) > > The series also force the inlining of some rte_memcpy > helpers, as by adding packed ring support, some of them > were not more inlined but embedded as functions in > the virtio_net object file, which was not expected. > > Finally, the series simplifies the descriptors buffers > prefetching, by doing it in the recently introduced > descriptor buffer mapping function. > > Maxime Coquelin (4): > vhost: un-inline dirty pages logging functions > vhost: do not inline packed and split functions > vhost: do not inline unlikely fragmented buffers code > vhost: simplify descriptor's buffer prefetching > > root (1): > eal/x86: force inlining of all memcpy and mov helpers > root ? "oops" :-) -- David Marchand
