On Aug 08, Alexander Lobakin wrote: > From: Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx> > Date: Thu, 8 Aug 2024 06:54:06 +0200 > > >> Hi Alexander, > >> > >> On Tue, Jun 28, 2022, at 12:47 PM, Alexander Lobakin wrote: > >>> cpumap has its own BH context based on kthread. It has a sane batch > >>> size of 8 frames per one cycle. > >>> GRO can be used on its own, adjust cpumap calls to the > >>> upper stack to use GRO API instead of netif_receive_skb_list() which > >>> processes skbs by batches, but doesn't involve GRO layer at all. > >>> It is most beneficial when a NIC which frame come from is XDP > >>> generic metadata-enabled, but in plenty of tests GRO performs better > >>> than listed receiving even given that it has to calculate full frame > >>> checksums on CPU. > >>> As GRO passes the skbs to the upper stack in the batches of > >>> @gro_normal_batch, i.e. 8 by default, and @skb->dev point to the > >>> device where the frame comes from, it is enough to disable GRO > >>> netdev feature on it to completely restore the original behaviour: > >>> untouched frames will be being bulked and passed to the upper stack > >>> by 8, as it was with netif_receive_skb_list(). > >>> > >>> Signed-off-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx> > >>> --- > >>> kernel/bpf/cpumap.c | 43 ++++++++++++++++++++++++++++++++++++++----- > >>> 1 file changed, 38 insertions(+), 5 deletions(-) > >>> > >> > >> AFAICT the cpumap + GRO is a good standalone improvement. I think > >> cpumap is still missing this. > > The only concern for having GRO in cpumap without metadata from the NIC > descriptor was that when the checksum status is missing, GRO calculates > the checksum on CPU, which is not really fast. > But I remember sometimes GRO was faster despite that. For the moment we could test it with UDP traffic with checksum disabled. Regards, Lorenzo > > >> > >> I have a production use case for this now. We want to do some intelligent > >> RX steering and I think GRO would help over list-ified receive in some cases. > >> We would prefer steer in HW (and thus get existing GRO support) but not all > >> our NICs support it. So we need a software fallback. > >> > >> Are you still interested in merging the cpumap + GRO patches? > > For sure I can revive this part. I was planning to get back to this > branch and pick patches which were not related to XDP hints and send > them separately. > > > > > Hi Daniel and Alex, > > > > Recently I worked on a PoC to add GRO support to cpumap codebase: > > - https://github.com/LorenzoBianconi/bpf-next/commit/a4b8264d5000ecf016da5a2dd9ac302deaf38b3e > > Here I added GRO support to cpumap through gro-cells. > > - https://github.com/LorenzoBianconi/bpf-next/commit/da6cb32a4674aa72401c7414c9a8a0775ef41a55 > > Here I added GRO support to cpumap trough napi-threaded APIs (with a some > > changes to them). > > Hmm, when I was testing it, adding a whole NAPI to cpumap was sorta > overkill, that's why I separated GRO structure from &napi_struct. > > Let me maybe find some free time, I would then test all 3 solutions > (mine, gro_cells, threaded NAPI) and pick/send the best? > > > > > Please note I have not run any performance tests so far, just verified it does > > not crash (I was planning to resume this work soon). Please let me know if it > > works for you. > > > > Regards, > > Lorenzo > > > >> > >> Thanks, > >> Daniel > > Thanks, > Olek >
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