From: Dave Hansen <dave.hansen@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>, Len Brown <lenb@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>, Willy Tarreau <w@1wt.eu>,
Andy Lutomirski <luto@kernel.org>,
Florian Weimer <fweimer@redhat.com>,
"Bae, Chang Seok" <chang.seok.bae@intel.com>,
X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
Rich Felker <dalias@libc.org>, Kyle Huey <me@kylehuey.com>,
Keno Fischer <keno@juliacomputing.com>,
Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features
Date: Thu, 20 May 2021 14:13:15 -0700 [thread overview]
Message-ID: <37833625-3e6b-5d93-cc4d-26164d06a0c6@intel.com> (raw)
In-Reply-To: <87k0ntazyn.ffs@nanos.tec.linutronix.de>
On 5/20/21 1:54 PM, Thomas Gleixner wrote:
>> Regarding error return for allocation failures.
>>
>> I'm not familiar with the use-case where vmalloc would be likely to fail today,
>> and I'd be interested if anybody can detail that use-case.
> It does not matter whether it's likely or not. Unlikely simply does not
> exist at cloud-scale.
Len, I may have led you astray in some of our discussions on this topic.
Here are the cold hard facts:
* vmalloc() can fail (the memory.kmem cgroup limit is probably the most
likely place to be exposed to this)
* vmalloc() failure in a fault (like #NM) will result in SIGSEGV
* vmalloc() failure in a syscall can be handled with -ENOMEM
In some of our discussions, I told you that reasonably-sized vmalloc()s
don't practically fail and that we shouldn't be concerned with failure
for our vmalloc()-in-#NM use-case. In other words, I'm OK with crashing
apps at the point that vmalloc() is failing.
However, Thomas was pretty clear that he's not OK with that. To
paraphrase: if we can avoid expanding the scope of where memory
allocation failures result in SIGSEGV, we should do it.
While I don't *entirely* agree that it's worth it, I can respect
Thomas's opinion here. It leads me in the direction of wanting to
drive dynamic xstate vmalloc()s from an explicit syscall ABI.
My apologies if I sent the AMX support on an unproductive tangent here.
next prev parent reply other threads:[~2021-05-20 21:13 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210415044258.GA6318@zn.tnic>
[not found] ` <20210415052938.GA2325@1wt.eu>
[not found] ` <20210415054713.GB6318@zn.tnic>
[not found] ` <CAJvTdKnjzAMh3N_c7KP3kA=e0LgYHgCANg44oJp3LcSm7dtbSQ@mail.gmail.com>
[not found] ` <20210419141454.GE9093@zn.tnic>
[not found] ` <CAJvTdK=p8mgO3xw9sRxu0c7NTNTG109M442b3UZh8TqLLfkC1Q@mail.gmail.com>
[not found] ` <20210419191539.GH9093@zn.tnic>
[not found] ` <CAJvTdK=VnG94ECcRVoUi8HrCbVEKc8X4_JmRTkqe+vTttf0Wsg@mail.gmail.com>
[not found] ` <20210419215809.GJ9093@zn.tnic>
[not found] ` <CAJvTdKn6JHo02karEs0e5g+6SimS5VUcXKjCkX35WY+xkgAgxw@mail.gmail.com>
[not found] ` <YIMmwhEr46VPAZa4@zn.tnic>
[not found] ` <CAJvTdKnhXnynybS4eNEF_EtF26auyb-mhKLNd1D9_zvCrchZsw@mail.gmail.com>
2021-05-17 9:45 ` Candidate Linux ABI for Intel AMX and hypothetical new related features Thomas Gleixner
2021-05-17 9:56 ` Florian Weimer
2021-05-17 10:18 ` Thomas Gleixner
2021-05-21 16:29 ` Len Brown
2021-05-17 13:49 ` Arjan van de Ven
2021-05-20 15:35 ` Len Brown
2021-05-20 20:54 ` Thomas Gleixner
2021-05-20 21:13 ` Dave Hansen [this message]
2021-05-20 21:41 ` Len Brown
2021-05-20 22:53 ` Dave Hansen
2021-05-21 9:41 ` Thomas Gleixner
2021-05-21 14:44 ` Florian Weimer
2021-05-21 14:49 ` Peter Zijlstra
2021-06-23 15:06 ` Florian Weimer
2021-06-23 23:11 ` Len Brown
2021-06-28 10:14 ` Enrico Weigelt, metux IT consult
2021-06-28 12:49 ` Florian Weimer
2021-06-30 12:22 ` Enrico Weigelt, metux IT consult
2021-06-30 12:41 ` Willy Tarreau
2021-06-30 13:55 ` Arjan van de Ven
2021-06-30 15:20 ` Len Brown
2021-06-30 15:25 ` Enrico Weigelt, metux IT consult
2021-05-21 16:14 ` Dave Hansen
2021-05-21 16:19 ` Florian Weimer
2021-05-21 16:26 ` Len Brown
2021-05-21 16:28 ` Dave Hansen
2021-05-21 16:31 ` Andy Lutomirski
2021-05-21 19:10 ` Thomas Gleixner
2021-05-21 20:07 ` Andy Lutomirski
2021-05-21 21:43 ` Thomas Gleixner
2021-05-21 22:07 ` Len Brown
2021-05-21 22:46 ` Thomas Gleixner
2021-05-21 23:31 ` Len Brown
2021-05-22 7:16 ` Florian Weimer
2021-05-22 23:55 ` Andy Lutomirski
2021-05-21 23:06 ` Dave Hansen
2021-05-21 23:08 ` Len Brown
2021-05-21 19:05 ` Thomas Gleixner
2021-05-20 21:22 ` Len Brown
2021-05-20 21:41 ` Thomas Gleixner
2021-05-20 21:49 ` Len Brown
2021-05-21 9:26 ` Thomas Gleixner
[not found] <CALCETrW2QHa2TLvnUuVxAAheqcbSZ-5_WRXtDSAGcbG8N+gtdQ@mail.gmail.com>
2021-03-26 23:18 ` Andy Lutomirski
2021-03-27 3:39 ` Len Brown
2021-03-27 9:14 ` Borislav Petkov
2021-03-27 9:58 ` Greg KH
2021-03-29 15:47 ` Len Brown
2021-03-29 16:38 ` Len Brown
2021-03-29 16:48 ` Florian Weimer
2021-03-29 18:14 ` Andy Lutomirski
2021-03-29 18:16 ` Andy Lutomirski
2021-03-29 22:38 ` Len Brown
2021-03-30 5:08 ` Andy Lutomirski
2021-03-30 5:50 ` Noah Goldstein
2021-03-30 17:01 ` Len Brown
2021-03-30 17:05 ` Andy Lutomirski
2021-03-30 17:56 ` Len Brown
2021-03-30 19:12 ` Dave Hansen
2021-03-30 20:20 ` Andy Lutomirski
2021-03-30 20:42 ` Len Brown
2021-03-30 22:01 ` David Laight
2021-03-31 16:31 ` Len Brown
2021-03-31 16:53 ` Andy Lutomirski
2021-03-31 21:42 ` Robert O'Callahan
2021-03-31 22:11 ` Len Brown
2021-03-31 22:28 ` Len Brown
2021-03-31 22:45 ` Andy Lutomirski
2021-04-09 20:52 ` Len Brown
2021-04-09 21:44 ` Andy Lutomirski
2021-04-11 19:07 ` Len Brown
2021-04-12 7:59 ` David Laight
2021-04-12 12:19 ` Borislav Petkov
2021-04-12 17:14 ` Sean Christopherson
2021-03-31 22:52 ` Borislav Petkov
2021-04-09 20:55 ` Len Brown
2021-03-28 0:53 ` Thomas Gleixner
2021-03-29 7:27 ` Peter Zijlstra
2021-03-29 15:06 ` Dave Hansen
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