> -----Original Message----- > From: Jakub Kicinski <kuba@xxxxxxxxxx> > Sent: Monday, April 17, 2023 1:52 PM > To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > Cc: linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Dexuan Cui > <decui@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Paul Rosswurm > <paulros@xxxxxxxxxxxxx>; olaf@xxxxxxxxx; vkuznets@xxxxxxxxxx; > davem@xxxxxxxxxxxxx; wei.liu@xxxxxxxxxx; edumazet@xxxxxxxxxx; > pabeni@xxxxxxxxxx; leon@xxxxxxxxxx; Long Li <longli@xxxxxxxxxxxxx>; > ssengar@xxxxxxxxxxxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; > daniel@xxxxxxxxxxxxx; john.fastabend@xxxxxxxxx; bpf@xxxxxxxxxxxxxxx; > ast@xxxxxxxxxx; Ajay Sharma <sharmaajay@xxxxxxxxxxxxx>; > hawk@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH V3,net-next, 3/4] net: mana: Enable RX path to handle > various MTU sizes > > On Sat, 15 Apr 2023 14:25:29 +0000 Haiyang Zhang wrote: > > > Allocating frag larger than a page is not safe. > > > > I saw other drivers doing this - use napi_alloc_frag for size bigger than a > page. > > And it returns compound page. Why it's not safe? Should we use other > allocator > > when need compound pages? > > I believe so. There was a thread about this within the last year. > Someone was trying to fix the page frag allocator to not fall back > to order 0 pages in case of failure if requested size is > PAGE_SIZE. > But there was push back and folks were saying that it's simply not > a case supported by the frag allocator. 🤷️ Thanks, I will use other allocator for compound pages. > > > > Frag allocator falls back to allocating single pages, doesn't it? > > > > Actually I checked it. Compound page is still returned for size smaller than > PAGE_SIZE, > > so I used single page allocation for that. > > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir > .bootlin.com%2Flinux%2Fv6.3- > rc6%2Fsource%2Fmm%2Fpage_alloc.c%23L5723&data=05%7C01%7Chaiyan > gz%40microsoft.com%7C00ca9f15ae314a4aa2ee08db3f6c8699%7C72f988 > bf86f141af91ab2d7cd011db47%7C1%7C0%7C638173507608724670%7C > Unknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJB > TiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=87QqFbWrxU > BMtqYpC397nlQxOJfU7lkt2%2FKAOGUjzjw%3D&reserved=0 > > Jumbo frames should really be supported as scatter transfers, > if possible. Our HW has much bigger overhead for scatter transfer on RX, so I use compound Page. Thanks, - Haiyang
