From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>,
npiggin@nick.local0.net,
Linus Torvalds <torvalds@linux-foundation.org>,
Jared Hulbert <jaredeh@gmail.com>,
Carsten Otte <cotte@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-mm@kvack.org
Subject: Re: [patch 0/7] [rfc] VM_MIXEDMAP, pte_special, xip work
Date: Wed, 12 Mar 2008 09:46:42 +0100 [thread overview]
Message-ID: <1205311602.28247.7.camel@localhost> (raw)
In-Reply-To: <200803121633.34539.nickpiggin@yahoo.com.au>
On Wed, 2008-03-12 at 16:33 +1100, Nick Piggin wrote:
> s390 is slightly different because it doesn't use a standard memory model
> but something more dynamic. It doesn't quite do the right thing here, so
> it uses pte_special. It could possibly tighten up pfn_valid, however I
> think there are various reasons why they don't want to (one is that they
> need to take a global lock in order to search their list of extents;
> which will suck for VM_MIXEDMAP performance).
Indeed. Under z/VM we have mappable memory segments named DCSS that can
have different types. Dependend on the type we either want to do
refcounting (exclusive write for memory hotplug) or not (read-only
shared for memory sharing). pfn_valid() would have to scan the list of
DCCSes to find out which type the segment has. That is way too
expensive.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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next prev parent reply other threads:[~2008-03-12 8:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-11 10:46 [patch 0/7] [rfc] VM_MIXEDMAP, pte_special, xip work npiggin
2008-03-11 10:46 ` [patch 1/7] mm: introduce VM_MIXEDMAP npiggin, Jared Hulbert
2008-03-11 10:46 ` [patch 2/7] mm: introduce pte_special pte bit npiggin
2008-03-11 10:46 ` [patch 3/7] mm: add vm_insert_mixed npiggin
2008-03-11 10:46 ` [patch 4/7] Alter the block device ->direct_access() API to work with the new get_xip_mem() API (that requires both kaddr and pfn are returned) npiggin
2008-03-11 10:46 ` [patch 5/7] xip: support non-struct page backed memory npiggin
2008-03-11 11:44 ` [patch 0/7] [rfc] VM_MIXEDMAP, pte_special, xip work Nick Piggin
2008-03-11 21:12 ` Jared Hulbert
2008-03-11 23:21 ` Nick Piggin
2008-03-12 4:35 ` Andrew Morton
2008-03-12 5:33 ` Nick Piggin
2008-03-12 8:46 ` Martin Schwidefsky [this message]
2008-03-12 16:40 ` Jared Hulbert
2008-03-12 17:10 ` Jared Hulbert
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