linux-kernel - Re: [PATCH 1/1] mm/vmalloc: Combine all TLB flush operations of KASAN shadow virtual address into one operation

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Message-ID: <CAHKZfL3PjWSEFRa3f6kBqx4YSsCWumK8zi0V1UEX_x+oDZZ1pQ@mail.gmail.com>
Date: Mon, 29 Jul 2024 19:12:15 +0800
From: Huang Adrian <adrianhuang0701@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, 
	Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Vincenzo Frascino <vincenzo.frascino@....com>, Uladzislau Rezki <urezki@...il.com>, 
	Christoph Hellwig <hch@...radead.org>, Baoquan He <bhe@...hat.com>, kasan-dev@...glegroups.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Adrian Huang <ahuang12@...ovo.com>, Jiwei Sun <sunjw10@...ovo.com>
Subject: Re: [PATCH 1/1] mm/vmalloc: Combine all TLB flush operations of KASAN
 shadow virtual address into one operation

On Mon, Jul 29, 2024 at 5:18 AM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Sat, 27 Jul 2024 00:52:46 +0800 Adrian Huang <adrianhuang0701@...il.com> wrote:
>
> > From: Adrian Huang <ahuang12@...ovo.com>
> >
> > When compiling kernel source 'make -j $(nproc)' with the up-and-running
> > KASAN-enabled kernel on a 256-core machine, the following soft lockup
> > is shown:
> >
> > ...
> >
> >         # CPU  DURATION                  FUNCTION CALLS
> >         # |     |   |                     |   |   |   |
> >           76) $ 50412985 us |    } /* __purge_vmap_area_lazy */
> >
> > ...
> >
> >      # CPU  DURATION                  FUNCTION CALLS
> >      # |     |   |                     |   |   |   |
> >        23) $ 1074942 us  |    } /* __purge_vmap_area_lazy */
> >        23) $ 1074950 us  |  } /* drain_vmap_area_work */
> >
> >   The worst execution time of drain_vmap_area_work() is about 1 second.
>
> Cool, thanks.
>
> But that's still pretty dreadful and I bet there are other workloads
> which will trigger the lockup detector in this path?

Yes, this path can be reproduced by other workloads. The stress-ng
command `stress-ng --exec $(nproc) --timeout 5m` can also trigger the
lockup detector in this path. (Confirmed on v6.11-rc1)

-- Adrian