> On Mon, May 15, 2023 at 01:24:20PM +0200, Lorenzo Bianconi wrote: > > > On 2023/5/12 21:08, Lorenzo Bianconi wrote: > > > > In order to reduce page_pool memory footprint, rely on > > > > page_pool_dev_alloc_frag routine and reduce buffer size > > > > (VETH_PAGE_POOL_FRAG_SIZE) to PAGE_SIZE / 2 in order to consume one page > > > > > > Is there any performance improvement beside the memory saving? As it > > > should reduce TLB miss, I wonder if the TLB miss reducing can even > > > out the cost of the extra frag reference count handling for the > > > frag support? > > > > reducing the requested headroom to 192 (from 256) we have a nice improvement in > > the 1500B frame case while it is mostly the same in the case of paged skb > > (e.g. MTU 8000B). > > Can you define 'nice improvement' ? ;) > Show us numbers or improvement in %. I am testing this RFC patch in the scenario reported below: iperf tcp tx --> veth0 --> veth1 (xdp_pass) --> iperf tcp rx - 6.4.0-rc1 net-next: MTU 1500B: ~ 7.07 Gbps MTU 8000B: ~ 14.7 Gbps - 6.4.0-rc1 net-next + page_pool frag support in veth: MTU 1500B: ~ 8.57 Gbps MTU 8000B: ~ 14.5 Gbps side note: it seems there is a regression between 6.2.15 and 6.4.0-rc1 net-next (even without latest veth page_pool patches) in the throughput I can get in the scenario above, but I have not looked into it yet. - 6.2.15: MTU 1500B: ~ 7.91 Gbps MTU 8000B: ~ 14.1 Gbps - 6.4.0-rc1 net-next w/o commits [0],[1],[2] MTU 1500B: ~ 6.38 Gbps MTU 8000B: ~ 13.2 Gbps Regards, Lorenzo [0] 0ebab78cbcbf net: veth: add page_pool for page recycling [1] 4fc418053ec7 net: veth: add page_pool stats [2] 9d142ed484a3 net: veth: rely on napi_build_skb in veth_convert_skb_to_xdp_buff > > > > > > > > > > for two 1500B frames. Reduce VETH_XDP_PACKET_HEADROOM to 192 from 256 > > > > (XDP_PACKET_HEADROOM) to fit max_head_size in VETH_PAGE_POOL_FRAG_SIZE. > > > > Please note, using default values (CONFIG_MAX_SKB_FRAGS=17), maximum > > > > supported MTU is now reduced to 36350B. > > > > > > Maybe we don't need to limit the frag size to VETH_PAGE_POOL_FRAG_SIZE, > > > and use different frag size depending on the mtu or packet size? > > > > > > Perhaps the page_pool_dev_alloc_frag() can be improved to return non-frag > > > page if the requested frag size is larger than a specified size too. > > > I will try to implement it if the above idea makes sense. > > > > > > > since there are no significant differences between full page and fragmented page > > implementation if the MTU is over the page boundary, does it worth to do so? > > (at least for the veth use-case). > > > > Regards, > > Lorenzo > > > >
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