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Date: Mon, 25 May 2020 11:43:00 +1000 From: "Anand K. Mistry" <amistry@...gle.com> To: Andi Kleen <ak@...ux.intel.com> Cc: linux-perf-users@...r.kernel.org, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>, Mark Rutland <mark.rutland@....com>, Namhyung Kim <namhyung@...nel.org>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3] perf record: Use an eventfd to wakeup when done On Sat, 23 May 2020 at 23:35, Andi Kleen <ak@...ux.intel.com> wrote: > > Anand K Mistry <amistry@...gle.com> writes: > > } > > > > + done_fd = eventfd(0, EFD_NONBLOCK); > > This will make perf depend on a recent glibc or other library > that implements eventfd. Wouldn't surprise me if some kind > of build time check is needed for this to pass all of Arnaldo's > built tests. Looks like Arnaldo made that change when merging: https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=e9db221d37f91409040cf7f3fbed08b44e055ae9 This makes me curious. How old a kernel should modern tools support? >From the man page, eventfd was added in 2.6.22 (and eventfd2 in 2.6.27), which was 2007 (or 2008 for eventfd2) and glibc-2.8 which was 2008. I understand the kernel's policy of never breaking userspace, but what about userspace tools? > > > -Andi -- Anand K. Mistry Software Engineer Google Australia
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