From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>, Ning Qu <quning@gmail.com>,
linux-mm <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
anton@samba.org, Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCHv3 1/2] mm: introduce vm_ops->map_pages()
Date: Fri, 28 Feb 2014 22:50:54 +1100 [thread overview]
Message-ID: <1393588254.22449.13.camel@pasglop> (raw)
In-Reply-To: <530FBD8F.7090304@linux.intel.com>
On Thu, 2014-02-27 at 14:34 -0800, Dave Hansen wrote:
>
> The question is really whether or not we ever access the mapping that we
> faulted around, though. If we never access it, then the cost (however
> small it was) is a loss. That's the mechanism that I'd expect causes
> Kirill's numbers to go up after they hit their minimum at ~order-4.
On the other hand, the cost of our faults on ppc64 is higher. The two hash
lookups by the MMU (generally L2 misses) before it even decides to take the
fault, followed by a generally longer code path before we get to Linux
fault handler.
So there might be a bigger win for us, especially if the "around" pages
get pre-hashed (ie, via update_mmu_cache)
I don't have the bandwidth to play around with that myself at the moment
but I'll try to find somebody who can.
Cheers,
Ben.
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next prev parent reply other threads:[~2014-02-28 11:50 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 19:53 [PATCHv3 0/2] mm: map few pages around fault address if they are in page cache Kirill A. Shutemov
2014-02-27 19:53 ` [PATCHv3 1/2] mm: introduce vm_ops->map_pages() Kirill A. Shutemov
2014-02-27 21:59 ` Dave Hansen
2014-02-27 22:06 ` Linus Torvalds
2014-02-27 22:34 ` Dave Hansen
2014-02-28 0:18 ` Kirill A. Shutemov
2014-02-28 11:50 ` Benjamin Herrenschmidt [this message]
2014-02-27 22:08 ` Andrew Morton
2014-03-03 23:16 ` Andrew Morton
2014-03-04 1:26 ` Kirill A. Shutemov
2014-03-05 0:04 ` Rusty Russell
2014-03-05 20:02 ` Andrew Morton
2014-07-24 3:33 ` Sasha Levin
2014-07-24 6:53 ` Andrey Ryabinin
2014-07-24 12:48 ` Sasha Levin
2014-07-24 13:05 ` Sasha Levin
2014-07-24 13:30 ` Konstantin Khlebnikov
2014-07-28 7:43 ` [PATCH] mm: don't allow fault_around_bytes to be 0 Andrey Ryabinin
2014-07-28 7:47 ` Andrey Ryabinin
2014-07-28 9:36 ` Kirill A. Shutemov
2014-07-28 10:27 ` Andrey Ryabinin
2014-07-28 10:52 ` Kirill A. Shutemov
2014-07-28 12:32 ` Sasha Levin
2014-07-28 22:43 ` David Rientjes
2014-07-28 15:26 ` Dave Hansen
2014-02-27 19:53 ` [PATCHv3 2/2] mm: implement ->map_pages for page cache Kirill A. Shutemov
2014-02-27 21:47 ` Andrew Morton
2014-02-28 0:31 ` Kirill A. Shutemov
2014-04-02 18:03 ` Konstantin Khlebnikov
2014-04-02 19:07 ` Kirill A. Shutemov
2014-02-27 21:28 ` [PATCHv3 0/2] mm: map few pages around fault address if they are in " Linus Torvalds
2014-02-28 0:10 ` Kirill A. Shutemov
2014-02-28 3:52 ` Wilcox, Matthew R
2014-02-28 23:08 ` Linus Torvalds
2014-03-12 14:22 ` Kirill A. Shutemov
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