Toke Høiland-Jørgensen <toke@xxxxxxxxxx> writes: > Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> writes: > >> Currently, when running xdp-trafficgen, test_run creates page_pools with >> the ptr_ring size of %NAPI_POLL_WEIGHT (64). >> This might work fine if XDP Tx queues are polled with the budget >> limitation. However, we often clear them with no limitation to ensure >> maximum free space when sending. >> For example, in ice and idpf (upcoming), we use "lazy" cleaning, i.e. we >> clean XDP Tx queue only when the free space there is less than 1/4 of >> the queue size. Let's take the ring size of 512 just as an example. 3/4 >> of the ring is 384 and often times, when we're entering the cleaning >> function, we have this whole amount ready (or 256 or 192, doesn't >> matter). >> Then we're calling xdp_return_frame_bulk() and after 64th frame, >> page_pool_put_page_bulk() starts returning pages to the page allocator >> due to that the ptr_ring is already full. put_page(), alloc_page() et at >> starts consuming a ton of CPU time and leading the board of the perf top >> output. >> >> Let's not limit ptr_ring to 64 for no real reason and allow more pages >> to be recycled. Just don't put anything to page_pool_params::size and >> let the Page Pool core pick the default of 1024 entries (I don't believe >> there are real use cases to clean more than that amount of descriptors). >> After the change, the MM layer disappears from the perf top output and >> all pages get recycled to the PP. On my test setup on idpf with the >> default ring size (512), this gives +80% of Tx performance with no >> visible memory consumption increase. >> >> Signed-off-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> > > Hmm, so my original idea with keeping this low was to avoid having a lot > of large rings lying around if it is used by multiple processes at once. > But we need to move away from the per-syscall allocation anyway, and > with Lorenzo's patches introducing a global system page pool we have an > avenue for that. So in the meantime, I have no objection to this... > > Reviewed-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> Actually, since Lorenzo's patches already landed in net-next, let's just move to using those straight away. I'll send a patch for this tomorrow :) -Toke
