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[212.51.140.210]) by smtp.gmail.com with ESMTPSA id d12-20020a5d644c000000b003142e438e8csm4100820wrw.26.2023.07.28.00.32.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Jul 2023 00:32:37 -0700 (PDT) Date: Fri, 28 Jul 2023 09:32:35 +0200 From: Adam Sindelar To: Yonghong Song Cc: bpf@vger.kernel.org, Adam Sindelar , David Vernet , Brendan Jackman , KP Singh , linux-kernel@vger.kernel.org, Alexei Starovoitov , Florent Revest Subject: Re: [PATCH bpf-next v4] libbpf: Expose API to consume one ring at a time Message-ID: References: <20230727083436.293201-1-adam@wowsignal.io> <38a585f1-fcbe-01ec-cc4c-63058b824f2f@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <38a585f1-fcbe-01ec-cc4c-63058b824f2f@linux.dev> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 27, 2023 at 03:11:00PM -0700, Yonghong Song wrote: > > > On 7/27/23 1:34 AM, Adam Sindelar wrote: > > We already provide ring_buffer__epoll_fd to enable use of external > > polling systems. However, the only API available to consume the ring > > buffer is ring_buffer__consume, which always checks all rings. When > > polling for many events, this can be wasteful. > > > > Signed-off-by: Adam Sindelar > > --- > > v1->v2: Added entry to libbpf.map > > v2->v3: Correctly set errno and handle overflow > > v3->v4: Fixed an embarrasing typo from zealous autocomplete > > > > tools/lib/bpf/libbpf.h | 1 + > > tools/lib/bpf/libbpf.map | 1 + > > tools/lib/bpf/ringbuf.c | 22 ++++++++++++++++++++++ > > 3 files changed, 24 insertions(+) > > Could you add a selftest to exercise ring_buffer__consume_ring()? > This way, people can better understand how this API could be used. > Yes, will do - I'll try to send out v5 with a test case this afternoon. As a note, I looked at the perf ring buffer API and it turns out Andrii Nakryiko saw the same problem and solved in a similar way in 2020. (See perf_buffer__consume_buffer). > > > > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h > > index 55b97b2087540..20ccc65eb3f9d 100644 > > --- a/tools/lib/bpf/libbpf.h > > +++ b/tools/lib/bpf/libbpf.h > > @@ -1195,6 +1195,7 @@ LIBBPF_API int ring_buffer__add(struct ring_buffer *rb, int map_fd, > > ring_buffer_sample_fn sample_cb, void *ctx); > > LIBBPF_API int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms); > > LIBBPF_API int ring_buffer__consume(struct ring_buffer *rb); > > +LIBBPF_API int ring_buffer__consume_ring(struct ring_buffer *rb, uint32_t ring_id); > > LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb); > [...]