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Date: Tue, 10 Nov 2020 08:12:54 +0100 From: Magnus Karlsson <magnus.karlsson@...il.com> To: John Fastabend <john.fastabend@...il.com> Cc: "Karlsson, Magnus" <magnus.karlsson@...el.com>, Björn Töpel <bjorn.topel@...el.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Network Development <netdev@...r.kernel.org>, Jonathan Lemon <jonathan.lemon@...il.com>, Maciej Fijalkowski <maciejromanfijalkowski@...il.com>, intel-wired-lan <intel-wired-lan@...ts.osuosl.org>, bpf <bpf@...r.kernel.org> Subject: Re: [Intel-wired-lan] [PATCH bpf-next 2/6] samples/bpf: increment Tx stats at sending On Mon, Nov 9, 2020 at 9:47 PM John Fastabend <john.fastabend@...il.com> wrote: > > Magnus Karlsson wrote: > > From: Magnus Karlsson <magnus.karlsson@...el.com> > > > > Increment the statistics over how many Tx packets have been sent at > > the time of sending instead of at the time of completion. This as a > > completion event means that the buffer has been sent AND returned to > > user space. The packet always gets sent shortly after sendto() is > > called. The kernel might, for performance reasons, decide to not > > return every single buffer to user space immediately after sending, > > for example, only after a batch of packets have been > > transmitted. Incrementing the number of packets sent at completion, > > will in that case be confusing as if you send a single packet, the > > counter might show zero for a while even though the packet has been > > transmitted. > > > > Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com> > > --- > > LGTM. Just one question then if we wanted to know the old value, packet > completion counter it looks like (tx_npkts - outstanding_tx) would give > that value? That is correct. > Acked-by: John Fastabend <john.fastabend@...il.com>
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