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From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Linus Torvalds" <torvalds@linux-foundation.org>,
	"Jeff Xu" <jeffxu@google.com>
Cc: "Michael Ellerman" <mpe@ellerman.id.au>,
	"Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Pedro Falcato" <pedro.falcato@gmail.com>,
	"kernel test robot" <oliver.sang@intel.com>,
	"Jeff Xu" <jeffxu@chromium.org>,
	oe-lkp@lists.linux.dev, lkp@intel.com,
	linux-kernel@vger.kernel.org,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Kees Cook" <keescook@chromium.org>,
	"Liam R. Howlett" <Liam.Howlett@oracle.com>,
	"Dave Hansen" <dave.hansen@intel.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Guenter Roeck" <groeck@chromium.org>,
	"Jann Horn" <jannh@google.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Jorge Lucangeli Obes" <jorgelo@chromium.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Muhammad Usama Anjum" <usama.anjum@collabora.com>,
	"Stephen Röttger" <sroettger@google.com>,
	"Suren Baghdasaryan" <surenb@google.com>,
	"Amer Al Shanawany" <amer.shanawany@gmail.com>,
	"Javier Carrasco" <javier.carrasco.cruz@gmail.com>,
	"Shuah Khan" <shuah@kernel.org>,
	linux-api@vger.kernel.org, linux-mm@kvack.org,
	ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com
Subject: Re: [linus:master] [mseal] 8be7258aad: stress-ng.pagemove.page_remaps_per_sec -4.4% regression
Date: Tue, 06 Aug 2024 09:24:56 +1000	[thread overview]
Message-ID: <D38D6LJZOIQK.2GV58PGVL5K85@gmail.com> (raw)
In-Reply-To: <CAHk-=wgySgXXkZtx49Xq70X2CmSizM8siacYKncMmFWRzKjs5Q@mail.gmail.com>

On Tue Aug 6, 2024 at 5:48 AM AEST, Linus Torvalds wrote:
> On Mon, 5 Aug 2024 at 12:38, Jeff Xu <jeffxu@google.com> wrote:
> >
> > I'm curious, why does ppc need to unmap vdso ? ( other archs don't
> > have unmap logic.)
>
> I have no idea. There are comments about 'perf' getting confused about
> mmap counts when 'context.vdso' isn't set up.
>
> But x86 has the same context.vdso logic, and does *not* set the
> pointer before installing the vma, for example. Also does not zero it
> out on munmap(), although it does have the mremap logic.
>
> For all I know it may all be entirely unnecessary, and could be
> removed entirely.

I don't know much about vdso code, it predated my involvedment in ppc.
Commit 83d3f0e90c6c8 says CRIU (checkpoint restore in userspace) is
moving it around. Why CRIU wants to do that, I don't know.

Can userspace on other archs not unmap their vdsos?

Thanks,
Nick

  parent reply	other threads:[~2024-08-05 23:25 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-08-04  8:59 [linus:master] [mseal] 8be7258aad: stress-ng.pagemove.page_remaps_per_sec -4.4% regression kernel test robot
2024-08-04 20:32 ` Linus Torvalds
2024-08-05 13:33   ` Pedro Falcato
2024-08-05 18:10     ` Jeff Xu
2024-08-05 18:55       ` Linus Torvalds
2024-08-05 19:33         ` Linus Torvalds
2024-08-06  2:14           ` Michael Ellerman
2024-08-06  2:17             ` Linus Torvalds
2024-08-06 12:03               ` Michael Ellerman
2024-08-06 14:43                 ` Linus Torvalds
2024-08-07 12:26                   ` Michael Ellerman
2024-08-06  6:04           ` Oliver Sang
2024-08-06 14:38             ` Linus Torvalds
2024-08-06 21:37             ` Pedro Falcato
2024-08-07  5:54               ` Oliver Sang
2024-08-05 19:37         ` Jeff Xu
2024-08-05 19:48           ` Linus Torvalds
2024-08-05 19:50             ` Linus Torvalds
2024-08-05 23:24             ` Nicholas Piggin [this message]
2024-08-06  0:13               ` Linus Torvalds
2024-08-06  1:22                 ` Jeff Xu
2024-08-06  2:01                 ` Michael Ellerman
2024-08-06  2:15                   ` Linus Torvalds
2024-09-13  5:47                   ` Christophe Leroy
2024-08-05 17:54   ` Jeff Xu
2024-08-05 13:56 ` Jeff Xu
2024-08-05 16:58 ` Jeff Xu
2024-08-06  1:44   ` Oliver Sang
2024-08-06 14:54     ` Jeff Xu

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