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From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <sasha.levin@oracle.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Dave Jones <davej@redhat.com>, Michal Hocko <mhocko@suse.cz>,
	Borislav Petkov <bp@alien8.de>,
	the arch/x86 maintainers <x86@kernel.org>
Subject: Re: Hang on large copy_from_user with PREEMPT_NONE
Date: Tue, 7 Apr 2015 11:31:45 +0200	[thread overview]
Message-ID: <20150407093145.GA10348@gmail.com> (raw)
In-Reply-To: <CA+55aFz8gByWhuAgW4fER8uw=q9E=tcN6LeS3YqCOqYsOfwPxA@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, Apr 6, 2015 at 12:08 PM, Sasha Levin <sasha.levin@oracle.com> wrote:
> >
> > Your patch just makes it hang in memset instead:
> 
> So it's certainly a big memset (2GB or so: original count in RDX: 
> 0x7e777000, and "%rcx << 6" is bytes left, so it has done about 85% 
> of it), which is certainly going to be slow, but it shouldn't 
> *hang*. [...]

Would be nice to see the actual kernel .config, as there's a few debug 
features that can slow things down significantly, such as 
CONFIG_KMEMCHECK=y or in some cases CONFIG_DEBUG_PAGEALLOC=y.

Thanks,

	Ingo

  parent reply	other threads:[~2015-04-07  9:31 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-06  3:59 Hang on large copy_from_user with PREEMPT_NONE Sasha Levin
2015-04-06 11:24 ` Borislav Petkov
2015-04-06 14:51   ` Sasha Levin
2015-04-06 16:52     ` Borislav Petkov
2015-04-06 17:26 ` Linus Torvalds
2015-04-06 19:08   ` Sasha Levin
2015-04-06 19:36     ` Borislav Petkov
2015-04-06 23:45       ` Sasha Levin
2015-04-06 20:42     ` Linus Torvalds
2015-04-07  1:49       ` Rusty Russell
2015-04-07  9:31       ` Ingo Molnar [this message]
2015-04-07 10:39         ` Borislav Petkov
2015-04-07 11:05           ` Ingo Molnar
2015-04-07 14:30             ` Michal Hocko
2015-04-07 14:37               ` Ingo Molnar
2015-04-07 17:00                 ` Sasha Levin
2015-04-07 17:33                   ` Linus Torvalds
2015-04-07 17:58                     ` Dave Jones
     [not found]                       ` <CA+55aFyxCb9aDfh0L4gyvHMSefOFoD7zftRpWbnvf5j9iZVaMw@mail.gmail.com>
2015-04-07 21:09                         ` Dave Jones

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