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From:   Marco Elver <elver@google.com>
Date:   Fri, 21 Oct 2022 00:37:26 -0700
Message-ID: <CANpmjNPUqVwHLVg5weN3+m7RJ7pCfDjBqJ2fBKueeMzKn=R=jA@mail.gmail.com>
Subject: Re: [PATCH v7 18/43] instrumented.h: add KMSAN support
To:     youling 257 <youling257@gmail.com>
Cc:     Alexander Potapenko <glider@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Biggers <ebiggers@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Thu, 20 Oct 2022 at 23:39, youling 257 <youling257@gmail.com> wrote:
>
> PerfTop:    8253 irqs/sec  kernel:75.3%  exact: 100.0% lost: 0/0 drop:
> 0/17899 [4000Hz cycles],  (all, 8 CPUs)
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>     14.87%  [kernel]              [k] 0xffffffff941d1f37
>      6.71%  [kernel]              [k] 0xffffffff942016cf
>
> what is 0xffffffff941d1f37?

You need to build with debug symbols:
CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y

Then it'll show function names.

> 2022-10-21 14:16 GMT+08:00, Marco Elver <elver@google.com>:
> > On Thu, 20 Oct 2022 at 22:55, youling 257 <youling257@gmail.com> wrote:
> >>
> >> How to use perf tool?
> >
> > The simplest would be to try just "perf top" - and see which kernel
> > functions consume most CPU cycles. I would suggest you compare both
> > kernels, and see if you can spot a function which uses more cycles% in
> > the problematic kernel.
> >