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>
