Message-ID: <B926444035E5E2439431908E3842AFD24B1D3C@DGGEMI525-MBS.china.huawei.com>
Date:   Wed, 20 May 2020 06:55:22 +0000
From:   Song Bao Hua <song.bao.hua@...ilicon.com>
To:     Alexandru Elisei <alexandru.elisei@....com>,
        Mark Rutland <mark.rutland@....com>,
        Lecopzer Chen <lecopzer@...il.com>
CC:     Sumit Garg <sumit.garg@...aro.org>,
        Jian-Lin Chen <lecopzer.chen@...iatek.com>,
        Will Deacon <will@...nel.org>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        "yj.chiang@...iatek.com" <yj.chiang@...iatek.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "acme@...nel.org" <acme@...nel.org>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "julien.thierry.kdev@...il.com" <julien.thierry.kdev@...il.com>,
        Linuxarm <linuxarm@...wei.com>
Subject: RE: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts

> 
> On 5/18/20 11:45 AM, Mark Rutland wrote:
> > Hi all,
> >
> > On Mon, May 18, 2020 at 02:26:00PM +0800, Lecopzer Chen wrote:
> >> HI Sumit,
> >>
> >> Thanks for your information.
> >>
> >> I've already implemented IPI (same as you did [1], little difference
> >> in detail), hardlockup detector and perf in last year(2019) for
> >> debuggability.
> >> And now we tend to upstream to reduce kernel maintaining effort.
> >> I'm glad if someone in ARM can do this work :)
> >>
> >> Hi Julien,
> >>
> >> Does any Arm maintainers can proceed this action?
> > Alexandru (Cc'd) has been rebasing and reworking Julien's patches,
> > which is my preferred approach.
> >
> > I understand that's not quite ready for posting since he's
> > investigating some of the nastier subtleties (e.g. mutual exclusion
> > with the NMI), but maybe we can put the work-in-progress patches
> > somewhere in the mean time.
> >
> > Alexandru, do you have an idea of what needs to be done, and/or when
> > you expect you could post that?
> 
> I'm currently working on rebasing the patches on top of 5.7-rc5, when I have
> something usable I'll post a link (should be a couple of days). After that I will
> address the review comments, and I plan to do a thorough testing because I'm
> not 100% confident that some of the assumptions around the locks that were
> removed are correct. My guess is this will take a few weeks.

+1
I would be awesome if perf NMI patches could be re-activated. Right now, it seems it is hard to
do "perf annotate" on a kernel function with local_irq disabled.

func()
{
local_irq_save();
.....
....
local_irq_restore();
return;
}

Perf will report all cycles are used by the last moment of the func().

Thanks,
Barry

> 
> Thanks,
> Alex
> >
> > Thanks,
> > Mark.
> >
> >> This is really useful in debugging.
> >> Thank you!!
> >>
> >>
> >>
> >> [1] https://lkml.org/lkml/2020/4/24/328
> >>
> >>
> >> Lecopzer
> >>
> >> Sumit Garg <sumit.garg@...aro.org> 於 2020年5月18日 週一 下午
> 1:46寫道：
> >>> + Julien
> >>>
> >>> Hi Lecopzer,
> >>>
> >>> On Sat, 16 May 2020 at 18:20, Lecopzer Chen <lecopzer@...il.com>
> wrote:
> >>>> These series implement Perf NMI funxtionality and depends on Pseudo
> >>>> NMI [1] which has been upstreamed.
> >>>>
> >>>> In arm64 with GICv3, Pseudo NMI was implemented for NMI-like
> interruts.
> >>>> That can be extended to Perf NMI which is the prerequisite for
> >>>> hard-lockup detector which had already a standard interface inside Linux.
> >>>>
> >>>> Thus the first step we need to implement perf NMI interface and
> >>>> make sure it works fine.
> >>>>
> >>> This is something that is already implemented via Julien's patch-set
> >>> [1]. Its v4 has been floating since July, 2019 and I couldn't find
> >>> any major blocking comments but not sure why things haven't
> >>> progressed further.
> >>>
> >>> Maybe Julien or Arm maintainers can provide updates on existing
> >>> patch-set [1] and how we should proceed further with this
> >>> interesting feature.
> >>>
> >>> And regarding hard-lockup detection, I have been able to enable it
> >>> based on perf NMI events using Julien's perf patch-set [1]. Have a
> >>> look at the patch here [2].
> >>>
> >>> [1] https://patchwork.kernel.org/cover/11047407/
> >>> [2]
> >>> http://lists.infradead.org/pipermail/linux-arm-kernel/2020-May/73222
> >>> 7.html
> >>>
> >>> -Sumit
> >>>
> >>>> Perf NMI has been test by dd if=/dev/urandom of=/dev/null like the
> >>>> link [2] did.
> >>>>
> >>>> [1] https://lkml.org/lkml/2019/1/31/535
> >>>> [2] https://www.linaro.org/blog/debugging-arm-kernels-using-nmifiq
> >>>>
> >>>>
> >>>> Lecopzer Chen (3):
> >>>>   arm_pmu: Add support for perf NMI interrupts registration
> >>>>   arm64: perf: Support NMI context for perf event ISR
> >>>>   arm64: Kconfig: Add support for the Perf NMI
> >>>>
> >>>>  arch/arm64/Kconfig             | 10 +++++++
> >>>>  arch/arm64/kernel/perf_event.c | 36 ++++++++++++++++++------
> >>>>  drivers/perf/arm_pmu.c         | 51
> ++++++++++++++++++++++++++++++----
> >>>>  include/linux/perf/arm_pmu.h   |  6 ++++
> >>>>  4 files changed, 88 insertions(+), 15 deletions(-)
> >>>>
> >>>> --
> >>>> 2.25.1

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