From: David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
To: npiggin-l3A5Bk7waGM@public.gmane.org
Cc: akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
shaggy-V7BBcbaFuwjMbYB6QlFGEg@public.gmane.org,
axboe-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org
Subject: Re: [patch 1/2]: x86: implement pte_special
Date: Thu, 27 Mar 2008 20:44:31 -0700 (PDT) [thread overview]
Message-ID: <20080327.204431.201380891.davem@davemloft.net> (raw)
In-Reply-To: <20080328033149.GD8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
From: Nick Piggin <npiggin-l3A5Bk7waGM@public.gmane.org>
Date: Fri, 28 Mar 2008 04:31:50 +0100
> Basically, the pfn-based mapping insertion (vm_insert_pfn, remap_pfn_range)
> calls pte_mkspecial. And that tells fast_gup "hands off".
I don't think it's wise to allocate a "soft PTE bit" for this on every
platform, especially for such a limited use case.
Is it feasible to test the page instead? Or are we talking about
cases where there may not be a backing page?
If the issue is to discern things like I/O mappings and such vs. real
pages, there are ways a platform can handle that without a special
bit.
That would leave us with real memory that does not have backing
page structs, and we have a way to test that too.
The special PTE bit seems superfluous to me.
WARNING: multiple messages have this Message-ID (diff)
From: David Miller <davem@davemloft.net>
To: npiggin@suse.de
Cc: akpm@linux-foundation.org, shaggy@austin.ibm.com,
axboe@oracle.com, linux-mm@kvack.org, linux-arch@vger.kernel.org,
torvalds@linux-foundation.org
Subject: Re: [patch 1/2]: x86: implement pte_special
Date: Thu, 27 Mar 2008 20:44:31 -0700 (PDT) [thread overview]
Message-ID: <20080327.204431.201380891.davem@davemloft.net> (raw)
Message-ID: <20080328034431.Llb8NBJysOQCqArTD_3d6YvOuUamcUCoI6OpfEMkrek@z> (raw)
In-Reply-To: <20080328033149.GD8083@wotan.suse.de>
From: Nick Piggin <npiggin@suse.de>
Date: Fri, 28 Mar 2008 04:31:50 +0100
> Basically, the pfn-based mapping insertion (vm_insert_pfn, remap_pfn_range)
> calls pte_mkspecial. And that tells fast_gup "hands off".
I don't think it's wise to allocate a "soft PTE bit" for this on every
platform, especially for such a limited use case.
Is it feasible to test the page instead? Or are we talking about
cases where there may not be a backing page?
If the issue is to discern things like I/O mappings and such vs. real
pages, there are ways a platform can handle that without a special
bit.
That would leave us with real memory that does not have backing
page structs, and we have a way to test that too.
The special PTE bit seems superfluous to me.
next prev parent reply other threads:[~2008-03-28 3:44 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-28 2:54 [patch 0/2]: lockless get_user_pages patchset Nick Piggin
2008-03-28 2:54 ` Nick Piggin
[not found] ` <20080328025455.GA8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-03-28 2:55 ` [patch 1/2]: x86: implement pte_special Nick Piggin
2008-03-28 2:55 ` Nick Piggin
[not found] ` <20080328025541.GB8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-03-28 3:23 ` David Miller
2008-03-28 3:23 ` David Miller
[not found] ` <20080327.202334.250213398.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
2008-03-28 3:31 ` Nick Piggin
2008-03-28 3:31 ` Nick Piggin
[not found] ` <20080328033149.GD8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-03-28 3:44 ` David Miller [this message]
2008-03-28 3:44 ` David Miller
[not found] ` <20080327.204431.201380891.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
2008-03-28 4:04 ` Nick Piggin
2008-03-28 4:04 ` Nick Piggin
[not found] ` <20080328040442.GE8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-03-28 4:09 ` David Miller
2008-03-28 4:09 ` David Miller
[not found] ` <20080327.210910.101408473.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
2008-03-28 4:15 ` Nick Piggin
2008-03-28 4:15 ` Nick Piggin
[not found] ` <20080328041519.GF8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-03-28 4:16 ` David Miller
2008-03-28 4:16 ` David Miller
[not found] ` <20080327.211632.02770342.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
2008-03-28 4:19 ` Nick Piggin
2008-03-28 4:19 ` Nick Piggin
2008-03-28 4:17 ` Nick Piggin
2008-03-28 4:17 ` Nick Piggin
2008-03-28 3:00 ` [patch 2/2]: introduce fast_gup Nick Piggin
2008-03-28 3:00 ` Nick Piggin
[not found] ` <20080328030023.GC8083-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-03-28 10:01 ` Jens Axboe
2008-03-28 10:01 ` Jens Axboe
2008-04-17 15:03 ` Peter Zijlstra
2008-04-17 15:03 ` Peter Zijlstra
2008-04-17 15:25 ` Linus Torvalds
2008-04-17 15:25 ` Linus Torvalds
[not found] ` <alpine.LFD.1.00.0804170814090.2879-5CScLwifNT1QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
2008-04-17 16:12 ` Peter Zijlstra
2008-04-17 16:12 ` Peter Zijlstra
2008-04-17 16:18 ` Linus Torvalds
2008-04-17 16:18 ` Linus Torvalds
[not found] ` <alpine.LFD.1.00.0804170916470.2879-5CScLwifNT1QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
2008-04-17 16:35 ` Peter Zijlstra
2008-04-17 16:35 ` Peter Zijlstra
2008-04-17 16:40 ` Linus Torvalds
2008-04-17 16:40 ` Linus Torvalds
[not found] ` <alpine.LFD.1.00.0804170940270.2879-5CScLwifNT1QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
2008-04-17 17:23 ` Peter Zijlstra
2008-04-17 17:23 ` Peter Zijlstra
2008-04-17 18:28 ` Linus Torvalds
2008-04-17 18:28 ` Linus Torvalds
[not found] ` <alpine.LFD.1.00.0804171127310.2879-5CScLwifNT1QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
2008-04-22 3:14 ` Nick Piggin
2008-04-22 3:14 ` Nick Piggin
2008-04-18 6:31 ` Geert Uytterhoeven
2008-04-18 6:31 ` Geert Uytterhoeven
2008-04-18 14:40 ` Linus Torvalds
2008-04-18 14:40 ` Linus Torvalds
2008-04-18 9:58 ` Jeremy Fitzhardinge
2008-04-18 9:58 ` Jeremy Fitzhardinge
2008-04-21 12:00 ` Avi Kivity
2008-04-21 12:00 ` Avi Kivity
[not found] ` <480C81C4.8030200-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2008-04-21 12:30 ` Peter Zijlstra
2008-04-21 12:30 ` Peter Zijlstra
2008-04-21 13:26 ` Avi Kivity
2008-04-21 13:26 ` Avi Kivity
[not found] ` <480C9619.2050201-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2008-04-21 14:35 ` Peter Zijlstra
2008-04-21 14:35 ` Peter Zijlstra
2008-04-22 3:23 ` Nick Piggin
2008-04-22 3:23 ` Nick Piggin
[not found] ` <20080422032319.GB21993-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2008-04-22 7:19 ` Avi Kivity
2008-04-22 7:19 ` Avi Kivity
2008-04-22 8:07 ` Ingo Molnar
2008-04-22 8:07 ` Ingo Molnar
2008-04-22 9:42 ` Peter Zijlstra
2008-04-22 9:42 ` Peter Zijlstra
2008-04-22 9:46 ` Nick Piggin
2008-04-22 9:46 ` Nick Piggin
2008-05-14 18:33 ` Dave Kleikamp
2008-05-15 1:13 ` Nick Piggin
-- strict thread matches above, loose matches on Subject: below --
2008-05-21 11:59 [patch 1/2] x86: implement pte_special Nick Piggin
2008-05-25 14:48 Nick Piggin
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