lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <0c1790dc-dbeb-8664-64ca-1f71e6c4f3a9@huawei.com> Date: Mon, 24 Apr 2023 19:58:07 +0800 From: Yunsheng Lin <linyunsheng@...wei.com> To: Lorenzo Bianconi <lorenzo.bianconi@...hat.com> CC: Lorenzo Bianconi <lorenzo@...nel.org>, <netdev@...r.kernel.org>, <bpf@...r.kernel.org>, <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>, <hawk@...nel.org>, <john.fastabend@...il.com>, <ast@...nel.org>, <daniel@...earbox.net> Subject: Re: [PATCH v2 net-next 1/2] net: veth: add page_pool for page recycling On 2023/4/24 17:17, Lorenzo Bianconi wrote: >> On 2023/4/23 22:20, Lorenzo Bianconi wrote: >>>> On 2023/4/23 2:54, Lorenzo Bianconi wrote: >>>>> struct veth_priv { >>>>> @@ -727,17 +729,20 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq, >>>>> goto drop; >>>>> >>>>> /* Allocate skb head */ >>>>> - page = alloc_page(GFP_ATOMIC | __GFP_NOWARN); >>>>> + page = page_pool_dev_alloc_pages(rq->page_pool); >>>>> if (!page) >>>>> goto drop; >>>>> >>>>> nskb = build_skb(page_address(page), PAGE_SIZE); >>>> >>>> If page pool is used with PP_FLAG_PAGE_FRAG, maybe there is some additional >>>> improvement for the MTU 1500B case, it seem a 4K page is able to hold two skb. >>>> And we can reduce the memory usage too, which is a significant saving if page >>>> size is 64K. >>> >>> please correct if I am wrong but I think the 1500B MTU case does not fit in the >>> half-page buffer size since we need to take into account VETH_XDP_HEADROOM. >>> In particular: >>> >>> - VETH_BUF_SIZE = 2048 >>> - VETH_XDP_HEADROOM = 256 + 2 = 258 >> >> On some arch the NET_IP_ALIGN is zero. >> >> I suppose XDP_PACKET_HEADROOM are for xdp_frame and data_meta, it seems >> xdp_frame is only 40 bytes for 64 bit arch and max size of metalen is 32 >> as xdp_metalen_invalid() suggest, is there any other reason why we need >> 256 bytes here? > > XDP_PACKET_HEADROOM must be greater than (40 + 32)B because you may want push > new data at the beginning of the xdp_buffer/xdp_frame running > bpf_xdp_adjust_head() helper. > I think 256B has been selected for XDP_PACKET_HEADROOM since it is 4 cachelines > (but I can be wrong). > There was a discussion in the past to reduce XDP_PACKET_HEADROOM to 192B but > this is not merged yet and it is not related to this series. We can address > your comments in a follow-up patch when XDP_PACKET_HEADROOM series is merged. It worth mentioning that the performance gain in this patch is at the cost of more memory usage, at most of VETH_RING_SIZE(256) + PP_ALLOC_CACHE_SIZE(128) pages is used. IMHO, it seems better to limit the memory usage as much as possible, or provide a way to disable/enable page pool for user.
Powered by blists - more mailing lists