Hi Florian,
On Thu, 13 May 2021 22:29:54 +0200
Florian Westphal <fw@xxxxxxxxx> wrote:
> This adds a nft_set_do_lookup() helper, then extends it to use
> direct calls when RETPOLINE feature is enabled.
>
> For non-retpoline builds, nft_set_do_lookup() inline helper
> does a indirect call. INDIRECT_CALLABLE_SCOPE macro allows to
> keep the lookup functions static in this case.
Thanks for doing this! And sorry I looked into it more than one year
ago without ever finishing it ;)
I ran some quick tests, I was curious to see the impact of dropping
indirect calls on that path. With the 'performance' test cases of
nft_concat_range.sh, roughly estimating clock cycles as clock frequency
divided by packet rate, it looks like this offsets entirely the usage of
retpolines!
With a 'return true;' in the lookup function (I patched nft_set_pipapo),
on my usual single AMD Epyc 7351 thread, 2.9GHz, average of three runs,
I get:
| packet | est. |
| rate | cycles |
| (Mpps) | |
-----------------------------------------------|--------|--------|
Without retpolines, netdev drop | 15.443 | 188 |
Without retpolines, dummy lookup function | 9.995 | 292 |
-> Without retpolines, set lookup | | 104-|-.
- - - - - - - - - - - - - - - - - - - - - - - -|- - - - | - - - -|
With retpolines, netdev drop | 10.420 | 278 | |
With retpolines, dummy lookup function | 7.038 | 412 |
-> With retpolines, set lookup | | 134 | |
- - - - - - - - - - - - - - - - - - - - - - - -|- - - - | - - - -|
This series, retpolines, netdev drop | 10.431 | 278 | |
This series, retpolines, dummy lookup function | 7.549 | 384 |
-> This series, retpolines, set lookup | ^ +7% | 106-|-'
estimated clock cycles for set lookup only are the difference between
cycles to hit the dummy lookup function and cycles to drop packets from
the netdev hook -- they're now approximately the same with and without
retpolines.
For context, I also ran the whole set of tests with actual matching.
This is indicative, just a single run:
--------------.-----------------------------------.--------------------------.
AMD Epyc 7351 | baselines, Mpps | this series |
1 thread |___________________________________|__________________________|
2.9GHz | | | | | | | |
512KiB L1D$ | netdev | hash | rbtree | | hash | rbtree | |
--------------| hook | no | single | | no | single | |
type entries | drop | ranges | field | pipapo | ranges | field | pipapo |
--------------|--------|--------|--------|--------|--------|-----------------|
net,port | | | | | +15% | +4% | +4% |
1000 | 10.1 | 5.2 | 2.7 | 4.6 | 6.0 | 2.8 | 4.8 |
--------------|--------|--------|--------|--------|--------|--------|--------|
port,net | | | | | +11% | +5% | +4% |
100 | 10.4 | 5.4 | 4.1 | 5.0 | 6.0 | 4.3 | 5.2 |
--------------|--------|--------|--------|--------|--------|--------|--------|
net6,port | | | | | +15% | +9% | +6% |
1000 | 10.0 | 4.6 | 1.1 | 3.1 | 9.9 | 1.2 | 3.3 |
--------------|--------|--------|--------|--------|--------|--------|--------|
port,proto | | | | | +7% | +3% | +3% |
10000 | 10.7 | 6.0 | 3.0 | 3.0 | 6.4 | 3.1 | 3.1 |
--------------|--------|--------|--------|--------|--------|--------|--------|
net6,port,mac | | | | | +3% | +4% | +3% |
10 | 9.9 | 3.8 | 2.7 | 3.3 | 3.9 | 2.8 | 3.4 |
--------------|--------|--------|--------|--------|--------|--------|--------|
net6,port,mac, | | | | | +3% | +9% | +4% |
proto 1000 | 10.0 | 3.6 | 1.1 | 2.4 | 3.7 | 1.2 | 2.5 |
--------------|--------|--------|--------|--------|--------|--------|--------|
net,mac | | | | | +6% | +4% | +3% |
1000 | 10.5 | 4.8 | 2.7 | 4.0 | 5.1 | 2.8 | 4.1 |
--------------'--------'--------'--------'--------'--------'--------'--------'
--
Stefano
