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Date: Fri, 15 Jan 2021 14:34:56 +0000 From: Alexander Lobakin <alobakin@...me> To: Eric Dumazet <edumazet@...gle.com> Cc: Alexander Lobakin <alobakin@...me>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Willem de Bruijn <willemb@...gle.com>, Miaohe Lin <linmiaohe@...wei.com>, Guillaume Nault <gnault@...hat.com>, Yunsheng Lin <linyunsheng@...wei.com>, Florian Westphal <fw@...len.de>, Steffen Klassert <steffen.klassert@...unet.com>, Dongseok Yi <dseok.yi@...sung.com>, Yadu Kishore <kyk.segfault@...il.com>, Al Viro <viro@...iv.linux.org.uk>, Marco Elver <elver@...gle.com>, Alexander Duyck <alexanderduyck@...com>, "Michael S. Tsirkin" <mst@...hat.com>, netdev <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH net] skbuff: back tiny skbs with kmalloc() in __netdev_alloc_skb() too From: Eric Dumazet <edumazet@...gle.com> Date: Fri, 15 Jan 2021 15:28:37 +0100 > On Fri, Jan 15, 2021 at 12:55 AM Alexander Lobakin <alobakin@...me> wrote: >> >> Commit 3226b158e67c ("net: avoid 32 x truesize under-estimation for >> tiny skbs") ensured that skbs with data size lower than 1025 bytes >> will be kmalloc'ed to avoid excessive page cache fragmentation and >> memory consumption. >> However, the same issue can still be achieved manually via >> __netdev_alloc_skb(), where the check for size hasn't been changed. >> Mirror the condition from __napi_alloc_skb() to prevent from that. >> >> Fixes: 3226b158e67c ("net: avoid 32 x truesize under-estimation for tiny skbs") > > No, this tag is wrong, if you fix a bug, bug is much older than linux-5.11 > > My fix was about GRO head and virtio_net heads, both using pre-sized > small buffers. > > You want to fix something else, and this is fine, because some drivers > are unfortunately > doing copy break ( at the cost of additional copy, even for packets > that might be consumed right away) You're right, it's about copybreak. I thought about wrong "Fixes" right after sending, but... Sorry. Will send v2 soon. Thanks, Al
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