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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>, Matt B <jackdachef@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	xfs@oss.sgi.com
Subject: Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing significant performance degradation.
Date: Mon, 2 Mar 2015 18:22:29 -0800	[thread overview]
Message-ID: <CA+55aFw+7V9DfxBA2_DhMNrEQOkvdwjFFga5Y67-a6yVeAz+NQ@mail.gmail.com> (raw)
In-Reply-To: <20150303014733.GL18360@dastard>

On Mon, Mar 2, 2015 at 5:47 PM, Dave Chinner <david@fromorbit.com> wrote:
>
> Anyway, the difference between good and bad is pretty clear, so
> I'm pretty confident the bisect is solid:
>
> 4d9424669946532be754a6e116618dcb58430cb4 is the first bad commit

Well, it's the mm queue from Andrew, so I'm not surprised. That said,
I don't see why that particular one should matter.

Hmm. In your profiles, can you tell which caller of "flush_tlb_page()"
 changed the most? The change from "mknnuma" to "prot_none" *should*
be 100% equivalent (both just change the page to be not-present, just
set different bits elsewhere in the pte), but clearly something
wasn't.

Oh. Except for that special "huge-zero-page" special case that got
dropped, but that got re-introduced in commit e944fd67b625.

There might be some other case where the new "just change the
protection" doesn't do the "oh, but it the protection didn't change,
don't bother flushing". I don't see it.

                          Linus

  reply	other threads:[~2015-03-03  2:22 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-02  1:04 Dave Chinner
2015-03-02 19:47 ` Linus Torvalds
2015-03-03  1:47   ` Dave Chinner
2015-03-03  2:22     ` Linus Torvalds [this message]
2015-03-03  2:37       ` Linus Torvalds
2015-03-03  5:20         ` Dave Chinner
2015-03-03  6:56           ` Linus Torvalds
2015-03-03 11:34             ` Dave Chinner
2015-03-03 13:43               ` Mel Gorman
2015-03-03 21:33                 ` Dave Chinner
2015-03-04 20:00                   ` Mel Gorman
2015-03-04 23:00                     ` Dave Chinner
2015-03-04 23:35                       ` Ingo Molnar
2015-03-04 23:51                         ` Dave Chinner
2015-03-02 19:17 Matt
2015-03-02 19:25 ` Dave Hansen
2015-03-02 19:45   ` Matt

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