netdev - Re: [PATCH bpf-next v8 1/3] bpf: remove extra lock_sock for TCP_ZEROCOPY

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Date:   Thu, 14 Jan 2021 20:28:39 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH bpf-next v8 1/3] bpf: remove extra lock_sock for TCP_ZEROCOPY_RECEIVE

On Thu, Jan 14, 2021 at 8:07 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Thu, Jan 14, 2021 at 8:05 PM Stanislav Fomichev <sdf@...gle.com> wrote:
> >
> > On Thu, Jan 14, 2021 at 7:57 PM Alexei Starovoitov
> > <alexei.starovoitov@...il.com> wrote:
> > >
> > > On Thu, Jan 14, 2021 at 7:40 PM Stanislav Fomichev <sdf@...gle.com> wrote:
> > > >
> > > > On Thu, Jan 14, 2021 at 7:27 PM Alexei Starovoitov
> > > > <alexei.starovoitov@...il.com> wrote:
> > > > >
> > > > > On Wed, Jan 13, 2021 at 1:33 PM Stanislav Fomichev <sdf@...gle.com> wrote:
> > > > > >
> > > > > > Add custom implementation of getsockopt hook for TCP_ZEROCOPY_RECEIVE.
> > > > > > We skip generic hooks for TCP_ZEROCOPY_RECEIVE and have a custom
> > > > > > call in do_tcp_getsockopt using the on-stack data. This removes
> > > > > > 3% overhead for locking/unlocking the socket.
> > > > > >
> > > > > > Without this patch:
> > > > > >      3.38%     0.07%  tcp_mmap  [kernel.kallsyms]  [k] __cgroup_bpf_run_filter_getsockopt
> > > > > >             |
> > > > > >              --3.30%--__cgroup_bpf_run_filter_getsockopt
> > > > > >                        |
> > > > > >                         --0.81%--__kmalloc
> > > > > >
> > > > > > With the patch applied:
> > > > > >      0.52%     0.12%  tcp_mmap  [kernel.kallsyms]  [k] __cgroup_bpf_run_filter_getsockopt_kern
> > > > > >
> > > > > > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > > > > > Cc: Martin KaFai Lau <kafai@...com>
> > > > > > Cc: Song Liu <songliubraving@...com>
> > > > > > Cc: Eric Dumazet <edumazet@...gle.com>
> > > > > > Acked-by: Martin KaFai Lau <kafai@...com>
> > > > >
> > > > > Few issues in this patch and the patch 2 doesn't apply:
> > > > > Switched to a new branch 'tmp'
> > > > > Applying: bpf: Remove extra lock_sock for TCP_ZEROCOPY_RECEIVE
> > > > > .git/rebase-apply/patch:295: trailing whitespace.
> > > > > #endif
> > > > > .git/rebase-apply/patch:306: trailing whitespace.
> > > > > union tcp_word_hdr {
> > > > > .git/rebase-apply/patch:309: trailing whitespace.
> > > > > };
> > > > > .git/rebase-apply/patch:311: trailing whitespace.
> > > > > #define tcp_flag_word(tp) ( ((union tcp_word_hdr *)(tp))->words [3])
> > > > > .git/rebase-apply/patch:313: trailing whitespace.
> > > > > enum {
> > > > > warning: squelched 1 whitespace error
> > > > > warning: 6 lines add whitespace errors.
> > > > > Applying: bpf: Try to avoid kzalloc in cgroup/{s,g}etsockopt
> > > > > error: patch failed: kernel/bpf/cgroup.c:1390
> > > > > error: kernel/bpf/cgroup.c: patch does not apply
> > > > > Patch failed at 0002 bpf: Try to avoid kzalloc in cgroup/{s,g}etsockopt
> > > > Sorry, I mentioned in the cover letter that the series requires
> > > > 4be34f3d0731 ("bpf: Don't leak memory in bpf getsockopt when optlen == 0")
> > > > which is only in the bpf tree. No sure when bpf & bpf-next merge.
> > > > Or are you trying to apply on top of that?
> > >
> > > hmm. It will take a while to wait for the trees to converge.
> > > Ok. I've cherry-picked that bpf commit and applied 3 patches on top,
> > > but the test failed to build:
> > >
> > > progs/sockopt_sk.c:60:47: error: use of undeclared identifier
> > > 'TCP_ZEROCOPY_RECEIVE'
> > >         if (ctx->level == SOL_TCP && ctx->optname == TCP_ZEROCOPY_RECEIVE) {
> > >                                                      ^
> > > progs/sockopt_sk.c:66:16: error: invalid application of 'sizeof' to an
> > > incomplete type 'struct tcp_zerocopy_receive'
> > >                 if (optval + sizeof(struct tcp_zerocopy_receive) > optval_end)
> > >
> > > Looks like copied uapi/tcp.h into tools/ wasn't in the include path.
> > Interesting, let me try to understand where it comes on my system
> > because it did work even without this uapi/tcp.h so I might
> > have messed something up. Thank you!
>
> You probably have a newer glibc. Mine is old. I think our CI doesn't
> use glibc and
> is probably missing the newest tcp.h as well.

Ah, it doesn't pick up my uapi/tcp.h because I include netinet/tcp.h
in the test :-(
Let me change that to linux/tcp.h and define SOL_TCP (because netinet/tcp.h
used to provide it and linux/tcp.h isn't). I'll retest and resend
tomorrow with a fresh head.
Sorry for the noise.