netdev - Re: [PATCH RESEND net-next v3] net: cache for same cpu skb_attempt_defer

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Message-ID: <CANn89iLUQ1DsBd_nemdhcgfvc_ybQmM_sGwWLwzeyOW+5C2KnA@mail.gmail.com>
Date: Fri, 5 Apr 2024 14:41:53 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Pavel Begunkov <asml.silence@...il.com>, netdev@...r.kernel.org, davem@...emloft.net, 
	dsahern@...nel.org, pabeni@...hat.com, kuba@...nel.org
Subject: Re: [PATCH RESEND net-next v3] net: cache for same cpu skb_attempt_defer_free

On Fri, Apr 5, 2024 at 2:38 PM Eric Dumazet <edumazet@...gle.com> wrote:

> There are false positives at this moment whenever frag_list are used in rx skbs.
>
> (Small MAX_SKB_FRAGS, small MTU, big GRO size)

 perf record -a -g -e skb:kfree_skb sleep 1
[ perf record: Woken up 84 times to write data ]
[ perf record: Captured and wrote 21.594 MB perf.data (95653 samples) ]

perf script

netserver 43113 [051] 2053323.508683: skb:kfree_skb:
skbaddr=0xffff8d699e0b8f00 protocol=34525 location=skb_release_data
reason: NOT_SPECIFIED
            7fffa5bcadb8 kfree_skb_list_reason ([kernel.kallsyms])
            7fffa5bcadb8 kfree_skb_list_reason ([kernel.kallsyms])
            7fffa5bcb7b8 skb_release_data ([kernel.kallsyms])
            7fffa5bcaa5f __kfree_skb ([kernel.kallsyms])
            7fffa5bd7099 skb_attempt_defer_free ([kernel.kallsyms])
            7fffa5ce81fa tcp_recvmsg_locked ([kernel.kallsyms])
            7fffa5ce7cf9 tcp_recvmsg ([kernel.kallsyms])
            7fffa5dac407 inet6_recvmsg ([kernel.kallsyms])
            7fffa5bb9bc2 sock_recvmsg ([kernel.kallsyms])
            7fffa5bbbc8b __sys_recvfrom ([kernel.kallsyms])
            7fffa5bbbd3a __x64_sys_recvfrom ([kernel.kallsyms])
            7fffa5eeb367 do_syscall_64 ([kernel.kallsyms])
            7fffa600312a entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                  1220d2 __libc_recv (/usr/grte/v3/lib64/libc-2.15.so)