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Merge tag 'mlx5-updates-2022-01-06' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux
Saeed Mahameed says:
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mlx5-updates-2022-01-06
1) Expose FEC per lane block counters via ethtool
2) Trivial fixes/updates/cleanup to mlx5e netdev driver
3) Fix htmldoc build warning
4) Spread mlx5 SFs (sub-functions) to all available CPU cores: Commits 1..5
Shay Drory Says:
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Before this patchset, mlx5 subfunction shared the same IRQs (MSI-X) with
their peers subfunctions, causing them to use same CPU cores.
In large scale, this is very undesirable, SFs use small number of cpu
cores and all of them will be packed on the same CPU cores, not
utilizing all CPU cores in the system.
In this patchset we want to achieve two things.
a) Spread IRQs used by SFs to all cpu cores
b) Pack less SFs in the same IRQ, will result in multiple IRQs per core.
In this patchset, we spread SFs over all online cpus available to mlx5
irqs in Round-Robin manner. e.g.: Whenever a SF is created, pick the next
CPU core with least number of SF IRQs bound to it, SFs will share IRQs on
the same core until a certain limit, when such limit is reached, we
request a new IRQ and add it to that CPU core IRQ pool, when out of IRQs,
pick any IRQ with least number of SF users.
This enhancement is done in order to achieve a better distribution of
the SFs over all the available CPUs, which reduces application latency,
as shown bellow.
Machine details:
Intel(R) Xeon(R) CPU E5-2697 v3 @ 2.60GHz with 56 cores.
PCI Express 3 with BW of 126 Gb/s.
ConnectX-5 Ex; EDR IB (100Gb/s) and 100GbE; dual-port QSFP28; PCIe4.0
x16.
Base line test description:
Single SF on the system. One instance of netperf is running on-top the
SF.
Numbers: latency = 15.136 usec, CPU Util = 35%
Test description:
There are 250 SFs on the system. There are 3 instances of netperf
running, on-top three different SFs, in parallel.
Perf numbers:
# netperf SFs latency(usec) latency CPU utilization
affinity affinity (lower is better) increase %
1 cpu=0 cpu={0} ~23 (app 1-3) 35% 75%
2 cpu=0,2,4 cpu={0} app 1: 21.625 30% 68% (CPU 0)
app 2-3: 16.5 9% 15% (CPU 2,4)
3 cpu=0 cpu={0,2,4} app 1: ~16 7% 84% (CPU 0)
app 2-3: ~17.9 14% 22% (CPU 2,4)
4 cpu=0,2,4 cpu={0,2,4} 15.2 (app 1-3) 0% 33% (CPU 0,2,4)
- The first two entries (#1 and #2) show current state. e.g.: SFs are
using the same CPU. The last two entries (#3 and #4) shows the latency
reduction improvement of this patch. e.g.: SFs are on different CPUs.
- Whenever we use several CPUs, in case there is a different CPU
utilization, write the utilization of each CPU separately.
- Whenever the latency result of the netperf instances were different,
write the latency of each netperf instances separately.
Commands:
- for netperf CPU=0:
$ for i in {1..3}; do taskset -c 0 netperf -H 1${i}.1.1.1 -t TCP_RR -- \
-o RT_LATENCY -r8 & done
- for netperf CPU=0,2,4
$ for i in {1..3}; do taskset -c $(( ($i - 1) * 2 )) netperf -H \
1${i}.1.1.1 -t TCP_RR -- -o RT_LATENCY -r8 & done
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Signed-off-by: 
David S. Miller <davem@davemloft.net>