Re: [PATCH] vt_buffer: drop console buffer copying optimisations

From: Dave Airlie <airlied@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	"dri-devel@lists.sf.net" <dri-devel@lists.sf.net>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Dave Airlie <airlied@redhat.com>
Subject: Re: [PATCH] vt_buffer: drop console buffer copying optimisations
Date: Fri, 30 Jan 2015 10:14:36 +1000	[thread overview]
Message-ID: <CAPM=9tzbZucODYHAGvXii=8HWeBRNWedAdWgk_mf4wB1s=zo4w__41370.1921621852$1422576927$gmane$org@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFwNSKEpEGexJbcqpLuRJPLMA2pb9Pr61ikxidwAX3Hcyg@mail.gmail.com>

On 30 January 2015 at 10:03, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Thu, Jan 29, 2015 at 3:57 PM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
>>
>> I can take this through the tty tree, but can I put it in linux-next and
>> wait for the 3.20 merge window to give people who might notice a
>> slow-down a chance to object?
>
> Yes. The problem only affects one (or a couple of) truly outrageously
> bad graphics cards that are only used in servers (because they are
> such crap that they wouldn't be acceptable anywhere else anyway), and
> they have afaik never worked with 64-bit kernels, so it's not even a
> regression.
>
> So it's worth fixing because it's a real - albeit very rare - problem
> (especially since the enhanched rep instruction model of memcpy could
> easily be *worse* than the 16-bit-at-a-time manual version), but I
> wouldn't consider it anywhere near high priority.
>
Totally not a priority, it just finally got tested for RHEL so I wanted to
make sure I posted it upstream before I forgot about it for months,

I also filed:
https://bugzilla.kernel.org/show_bug.cgi?id=92311

since the RH bug is private and full of crap, that bug contains
a screenshot of the remote console to see what sort of crap it produces.

Dave.

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