From: Nick Piggin <npiggin@suse.de>
To: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: "mingo@elte.hu" <mingo@elte.hu>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"hpa@zytor.com" <hpa@zytor.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"hugh@veritas.com" <hugh@veritas.com>,
"arjan@infradead.org" <arjan@infradead.org>,
"jbarnes@virtuousgeek.org" <jbarnes@virtuousgeek.org>,
"rdreier@cisco.com" <rdreier@cisco.com>,
"jeremy@goop.org" <jeremy@goop.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Siddha, Suresh B" <suresh.b.siddha@intel.com>
Subject: Re: [patch 1/7] x86 PAT: store vm_pgoff for all linear_over_vma_region mappings - v3
Date: Thu, 18 Dec 2008 23:33:03 +0100 [thread overview]
Message-ID: <20081218223303.GK10681@wotan.suse.de> (raw)
In-Reply-To: <20081218221057.GA3331@linux-os.sc.intel.com>
On Thu, Dec 18, 2008 at 02:10:57PM -0800, Pallipadi, Venkatesh wrote:
> On Thu, Dec 18, 2008 at 01:27:28PM -0800, Nick Piggin wrote:
> >
> > This is fine by me, however:
> > 1. Can you add some comments to say "this is not for core vm but for pat,
> > oh and a pgoff of zero is not going to work".
>
> OK. Will add comments about both the points.
>
> > 2. Can you please justify to me (or the changelog) roughly why PAT wants
> > to know if the mapping is linear or not? Presumably it has to handle
> > both types? If performance wasn't an issue, then you could manually scan
> > the ptes to verify (which would solve your zero-offset bug). etc.
>
> The main reason is performance. If we know it is linear, we can track the entire
> region as one block and do the reserve free for entire region. But, if it is
> not linear, then we have to reserve memtype of physical addresses page by page.
> This will not be optimal as it will result in reserve and free becoming
> slower. Almost all users that we find in kernel today (atleast in x86) are
> all linear.
OK, so it is not a bug to miss the zero pgoff case then. That's good
to know and should be added to comments.
next prev parent reply other threads:[~2008-12-18 22:33 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-18 19:41 [patch 0/7] x86 PAT: track pfnmap mappings with remap_pfn_range vm_insert_pfn " venkatesh.pallipadi
2008-12-18 19:41 ` [patch 1/7] x86 PAT: store vm_pgoff for all linear_over_vma_region mappings " venkatesh.pallipadi
2008-12-18 21:27 ` Nick Piggin
2008-12-18 22:10 ` Pallipadi, Venkatesh
2008-12-18 22:33 ` Nick Piggin [this message]
2008-12-18 19:41 ` [patch 2/7] x86 PAT: Add follow_pfnmp_pte routine to help tracking pfnmap pages " venkatesh.pallipadi
2008-12-18 21:31 ` Nick Piggin
2008-12-18 22:15 ` Pallipadi, Venkatesh
2008-12-18 19:41 ` [patch 3/7] x86 PAT: hooks in generic vm code to help archs to track pfnmap regions " venkatesh.pallipadi
2008-12-18 21:35 ` Nick Piggin
2008-12-18 22:23 ` Pallipadi, Venkatesh
2008-12-18 19:41 ` [patch 4/7] x86 PAT: Implement track/untrack of pfnmap regions for x86 " venkatesh.pallipadi
2008-12-18 21:38 ` Nick Piggin
2008-12-18 21:40 ` H. Peter Anvin
2008-12-18 21:46 ` Ingo Molnar
2008-12-18 21:53 ` Pallipadi, Venkatesh
2008-12-18 19:41 ` [patch 5/7] x86 PAT: change pgprot_noncached to uc_minus instead of strong uc " venkatesh.pallipadi
2008-12-18 19:41 ` [patch 6/7] x86 PAT: add pgprot_writecombine() interface for drivers " venkatesh.pallipadi
2008-12-18 19:41 ` [patch 7/7] x86 PAT: update documentation to cover pgprot and remap_pfn related changes " venkatesh.pallipadi
2008-12-18 21:13 ` Randy Dunlap
2008-12-18 21:49 ` Pallipadi, Venkatesh
2008-12-18 21:53 ` Randy Dunlap
2008-12-18 22:03 ` Pallipadi, Venkatesh
2008-12-18 21:17 ` [patch 0/7] x86 PAT: track pfnmap mappings with remap_pfn_range vm_insert_pfn " H. Peter Anvin
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