From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Richard Henderson <rth@twiddle.net>,
Russell King <linux@armlinux.org.uk>,
Will Deacon <will.deacon@arm.com>,
Haavard Skinnemoen <hskinnemoen@gmail.com>,
Steven Miao <realmz6@gmail.com>,
Jesper Nilsson <jesper.nilsson@axis.com>,
Mark Salter <msalter@redhat.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
"Richard Kuo" <rkuo@codeaurora.org>,
Tony Luck <tony.luck@intel.com>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
James Hogan <james.hogan@imgtec.com>,
Michal Simek <monstr@monstr.eu>,
David Howells <dhowells@redhat.com>,
"Ley Foon Tan" <lftan@altera.com>,
Jonas Bonn <Jonas.Nilsson@synopsys.com>
Subject: Re: [RFC][CFT][PATCHSET v1] uaccess unification
Date: Wed, 29 Mar 2017 17:02:45 -0700 [thread overview]
Message-ID: <09ead054-f62a-76e2-88e0-8d18592d2604@synopsys.com> (raw)
In-Reply-To: <20170329234246.GL29622@ZenIV.linux.org.uk>
On 03/29/2017 04:42 PM, Al Viro wrote:
> On Wed, Mar 29, 2017 at 02:14:22PM -0700, Vineet Gupta wrote:
>
>>> BTW, I wonder if inlining all of the copy_{to,from}_user() is actually a win.
>>
>> Just to be clear, your series was doing this for everyone.
>
> Huh? It's just that most of architectures *were* inlining that;
> arc change was unintentional (copy_from_user/copy_to_user went
> uninlined, which your patch deals with), but it's not that I'm forcing
> inlining on every architecture out there.
That is correct - I didn't mean to say you changed it per-se , but that I saw
INLINE_COPY* all over the place but not for ARC :-)
>>> It might
>>> end up being a win, but that's not apriori obvious... Do you have any
>>> profiling results in that area?
>>
>> Unfortunately not at the moment. The reason for adding out-of-line variant was not
>> so much as performance but to improve the footprint for -Os case (some customer I
>> think).
>
> Just to make it clear - I'm less certain than Linus that uninlined is uniformly
> better, but I have a strong suspicion that on most architectures it *is*.
> And not just in terms of kernel size - I would expect better speed as well.
> The only reason why these knobs are there is that I want to separate the
> "who should switch to uninlined" from this series and allow for the possibility
> that for some architectures inlined will really turn out to be better.
> I do _not_ expect that there'll be many of those; if it turns out that there's
> none, I'll be only glad to make the guts of copy_{to,from}_user() always
> out of line.
>
> IOW your patch reverts an unintentional change of behaviour, but I really
> wonder if that (out-of-line guts of copy_{to,from}_user) isn't an overall
> win for arc. I've applied your patch, but it would be nice if you could
> arrange for testing with and without inlining and post the results. The
> same goes for all architectures; again, I would expect out-of-line to end up
> a win on most of them.
I guess I can in next day or two - but mind you the inline version for ARC is kind
of special vs. other arches. We have this "manual" constant propagation to elide
the unrolled LD/ST for 1-15 byte stragglers, when @sz is constant. In the
out-of-line version, we loose all of that and the code needs to fall thru all the
cases. We can possibly improve that by re-arranging the checks - so exit early if
no stragglers etc ...
next prev parent reply other threads:[~2017-03-30 0:03 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-29 5:57 [RFC][CFT][PATCHSET v1] uaccess unification Al Viro
2017-03-29 20:08 ` Vineet Gupta
2017-03-29 20:29 ` Al Viro
2017-03-29 20:37 ` Linus Torvalds
2017-03-29 21:03 ` Al Viro
2017-03-29 21:24 ` Linus Torvalds
2017-03-29 23:09 ` Al Viro
2017-03-29 23:43 ` Linus Torvalds
2017-03-30 15:31 ` Al Viro
2017-03-29 21:14 ` Vineet Gupta
2017-03-29 23:42 ` Al Viro
2017-03-30 0:02 ` Vineet Gupta [this message]
2017-03-30 0:27 ` Linus Torvalds
2017-03-30 1:15 ` Al Viro
2017-03-30 20:40 ` Vineet Gupta
2017-03-30 20:59 ` Linus Torvalds
2017-03-30 23:21 ` Russell King - ARM Linux
2017-03-30 12:32 ` Martin Schwidefsky
2017-03-30 14:48 ` Al Viro
2017-03-30 16:22 ` Russell King - ARM Linux
2017-03-30 16:43 ` Al Viro
2017-03-30 17:18 ` Linus Torvalds
2017-03-30 18:48 ` Al Viro
2017-03-30 18:54 ` Al Viro
2017-03-30 18:59 ` Linus Torvalds
2017-03-30 19:10 ` Al Viro
2017-03-30 19:19 ` Linus Torvalds
2017-03-30 21:08 ` Al Viro
2017-03-30 18:56 ` Linus Torvalds
2017-03-31 0:21 ` Kees Cook
2017-03-31 13:38 ` James Hogan
2017-04-03 16:27 ` James Morse
2017-04-04 20:26 ` Max Filippov
2017-04-04 20:52 ` Al Viro
2017-04-05 5:05 ` ia64 exceptions (Re: [RFC][CFT][PATCHSET v1] uaccess unification) Al Viro
2017-04-05 8:08 ` Al Viro
2017-04-05 18:44 ` Tony Luck
2017-04-05 20:33 ` Al Viro
2017-04-07 0:24 ` [RFC][CFT][PATCHSET v2] uaccess unification Al Viro
2017-04-07 0:35 ` Al Viro
[not found] <CACVxJT8+fQqvpSPb9rTWFy6g7moqUqxi+Ewjcg0ykuqo=vm4Ow@mail.gmail.com>
2017-03-30 13:27 ` [RFC][CFT][PATCHSET v1] " Alexey Dobriyan
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