+ kmap-types-clean-up-and-optimization.patch added to -mm tree

+ kmap-types-clean-up-and-optimization.patch added to -mm tree

[akpm]

The patch titled
     kmap-types: clean up and optimization
has been added to the -mm tree.  Its filename is
     kmap-types-clean-up-and-optimization.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: kmap-types: clean up and optimization
From: "Jan Beulich" <JBeulich@novell.com>

Several of the types aren't being used at all anymore - those can be
deleted altogether.  Others are used only by single components that can be
assumed to be enabled everywhere, so those are made dependent upon
CONFIG_* settings.  Since this somewhat conflicts with the sequential gap
markers used under __WITH_KM_FENCE, and since this can be simplified
anyway, fold the enumerator definitions with the (modified accordingly)
KMAP_D() macro always.

The whole point of the reduction is that, at least on ix86, the number of
kmap types can (depending on configuration) affect the amount of low
memory, and thus unused types should be avoided if possible.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm/include/asm/kmap_types.h     |    6 --
 arch/powerpc/include/asm/kmap_types.h |   11 ----
 arch/tile/include/asm/kmap_types.h    |    5 --
 include/asm-generic/kmap_types.h      |   53 +++++++++++-------------
 4 files changed, 26 insertions(+), 49 deletions(-)

diff -puN arch/arm/include/asm/kmap_types.h~kmap-types-clean-up-and-optimization arch/arm/include/asm/kmap_types.h
--- a/arch/arm/include/asm/kmap_types.h~kmap-types-clean-up-and-optimization
+++ a/arch/arm/include/asm/kmap_types.h
@@ -24,10 +24,4 @@ enum km_type {
 	KM_TYPE_NR
 };
 
-#ifdef CONFIG_DEBUG_HIGHMEM
-#define KM_NMI		(-1)
-#define KM_NMI_PTE	(-1)
-#define KM_IRQ_PTE	(-1)
-#endif
-
 #endif
diff -puN arch/powerpc/include/asm/kmap_types.h~kmap-types-clean-up-and-optimization arch/powerpc/include/asm/kmap_types.h
--- a/arch/powerpc/include/asm/kmap_types.h~kmap-types-clean-up-and-optimization
+++ a/arch/powerpc/include/asm/kmap_types.h
@@ -30,16 +30,5 @@ enum km_type {
 	KM_TYPE_NR
 };
 
-/*
- * This is a temporary build fix that (so they say on lkml....) should no longer
- * be required after 2.6.33, because of changes planned to the kmap code.
- * Let's try to remove this cruft then.
- */
-#ifdef CONFIG_DEBUG_HIGHMEM
-#define KM_NMI		(-1)
-#define KM_NMI_PTE	(-1)
-#define KM_IRQ_PTE	(-1)
-#endif
-
 #endif	/* __KERNEL__ */
 #endif	/* _ASM_POWERPC_KMAP_TYPES_H */
diff -puN arch/tile/include/asm/kmap_types.h~kmap-types-clean-up-and-optimization arch/tile/include/asm/kmap_types.h
--- a/arch/tile/include/asm/kmap_types.h~kmap-types-clean-up-and-optimization
+++ a/arch/tile/include/asm/kmap_types.h
@@ -45,12 +45,7 @@ enum {
 	KM_IRQ1,
 	KM_SOFTIRQ0,
 	KM_SOFTIRQ1,
-	KM_SYNC_ICACHE,
-	KM_SYNC_DCACHE,
 	KM_UML_USERCOPY,
-	KM_IRQ_PTE,
-	KM_NMI,
-	KM_NMI_PTE,
 	KM_KDB
 };
 
diff -puN include/asm-generic/kmap_types.h~kmap-types-clean-up-and-optimization include/asm-generic/kmap_types.h
--- a/include/asm-generic/kmap_types.h~kmap-types-clean-up-and-optimization
+++ a/include/asm-generic/kmap_types.h
@@ -2,37 +2,36 @@
 #define _ASM_GENERIC_KMAP_TYPES_H
 
 #ifdef __WITH_KM_FENCE
-# define KMAP_D(n) __KM_FENCE_##n ,
+# define KMAP_D(n) __KM_FENCE_##n, KM_##n
 #else
-# define KMAP_D(n)
+# define KMAP_D(n) KM_##n
 #endif
 
 enum km_type {
-KMAP_D(0)	KM_BOUNCE_READ,
-KMAP_D(1)	KM_SKB_SUNRPC_DATA,
-KMAP_D(2)	KM_SKB_DATA_SOFTIRQ,
-KMAP_D(3)	KM_USER0,
-KMAP_D(4)	KM_USER1,
-KMAP_D(5)	KM_BIO_SRC_IRQ,
-KMAP_D(6)	KM_BIO_DST_IRQ,
-KMAP_D(7)	KM_PTE0,
-KMAP_D(8)	KM_PTE1,
-KMAP_D(9)	KM_IRQ0,
-KMAP_D(10)	KM_IRQ1,
-KMAP_D(11)	KM_SOFTIRQ0,
-KMAP_D(12)	KM_SOFTIRQ1,
-KMAP_D(13)	KM_SYNC_ICACHE,
-KMAP_D(14)	KM_SYNC_DCACHE,
-/* UML specific, for copy_*_user - used in do_op_one_page */
-KMAP_D(15)	KM_UML_USERCOPY,
-KMAP_D(16)	KM_IRQ_PTE,
-KMAP_D(17)	KM_NMI,
-KMAP_D(18)	KM_NMI_PTE,
-KMAP_D(19)	KM_KDB,
-/*
- * Remember to update debug_kmap_atomic() when adding new kmap types!
- */
-KMAP_D(20)	KM_TYPE_NR
+	KMAP_D(BOUNCE_READ),
+#if defined(CONFIG_SUNRPC) || defined(CONFIG_SUNRPC_MODULE)
+	KMAP_D(SKB_SUNRPC_DATA),
+#endif
+	KMAP_D(SKB_DATA_SOFTIRQ),
+	KMAP_D(USER0),
+	KMAP_D(USER1),
+	KMAP_D(BIO_SRC_IRQ),
+	KMAP_D(BIO_DST_IRQ),
+#if defined(CONFIG_X86) && defined(CONFIG_CRASH_DUMP)
+	KMAP_D(PTE0),
+#endif
+	KMAP_D(IRQ0),
+	KMAP_D(IRQ1),
+	KMAP_D(SOFTIRQ0),
+	KMAP_D(SOFTIRQ1),
+#ifdef CONFIG_UML /* for copy_*_user - used in do_op_one_page */
+	KMAP_D(UML_USERCOPY),
+#endif
+#ifdef CONFIG_KGDB_KDB
+	KMAP_D(KDB),
+#endif
+
+	KMAP_D(TYPE_NR)
 };
 
 #undef KMAP_D
_

Patches currently in -mm which might be from JBeulich@novell.com are

linux-next.patch
kmap-types-clean-up-and-optimization.patch

Re: + kmap-types-clean-up-and-optimization.patch added to -mm tree

[Peter Zijlstra]

On Wed, 2010-12-22 at 14:48 -0800, akpm@linux-foundation.org wrote:
> The patch titled
>      kmap-types: clean up and optimization
> has been added to the -mm tree.  Its filename is
>      kmap-types-clean-up-and-optimization.patch
> 
> Before you just go and hit "reply", please:
>    a) Consider who else should be cc'ed
>    b) Prefer to cc a suitable mailing list as well
>    c) Ideally: find the original patch on the mailing list and do a
>       reply-to-all to that, adding suitable additional cc's
> 

> ------------------------------------------------------
> Subject: kmap-types: clean up and optimization
> From: "Jan Beulich" <JBeulich@novell.com>
> 
> Several of the types aren't being used at all anymore - those can be
> deleted altogether.  

NO! That's wrong, in fact non of them are being used, but removing them
will decrease the number of kmap_atomic slots, but those are still being
used.

> Others are used only by single components that can be
> assumed to be enabled everywhere, so those are made dependent upon
> CONFIG_* settings.  Since this somewhat conflicts with the sequential gap
> markers used under __WITH_KM_FENCE, and since this can be simplified
> anyway, fold the enumerator definitions with the (modified accordingly)
> KMAP_D() macro always.
> 
> The whole point of the reduction is that, at least on ix86, the number of
> kmap types can (depending on configuration) affect the amount of low
> memory, and thus unused types should be avoided if possible.

Feh, its only a few pages and since there is no way to actually tell if
you've got enough kmap atomic pages other than experiencing runtime
errors, removing them must be done with utmost prudence.

> Signed-off-by: Jan Beulich <jbeulich@novell.com>

Nacked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

Re: + kmap-types-clean-up-and-optimization.patch added to -mm tree

[Jan Beulich]

>>> On 23.12.10 at 10:58, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Wed, 2010-12-22 at 14:48 -0800, akpm@linux-foundation.org wrote:
>> The patch titled
>>      kmap-types: clean up and optimization
>> has been added to the -mm tree.  Its filename is
>>      kmap-types-clean-up-and-optimization.patch
>> 
>> Before you just go and hit "reply", please:
>>    a) Consider who else should be cc'ed
>>    b) Prefer to cc a suitable mailing list as well
>>    c) Ideally: find the original patch on the mailing list and do a
>>       reply-to-all to that, adding suitable additional cc's
>> 
> 
>> ------------------------------------------------------
>> Subject: kmap-types: clean up and optimization
>> From: "Jan Beulich" <JBeulich@novell.com>
>> 
>> Several of the types aren't being used at all anymore - those can be
>> deleted altogether.  
> 
> NO! That's wrong, in fact non of them are being used, but removing them
> will decrease the number of kmap_atomic slots, but those are still being
> used.

Would you mind pointing out examples of such uses (i.e. without
the proper enumerator)? How would those avoid collisions with
actually used slots?

>> Others are used only by single components that can be
>> assumed to be enabled everywhere, so those are made dependent upon
>> CONFIG_* settings.  Since this somewhat conflicts with the sequential gap
>> markers used under __WITH_KM_FENCE, and since this can be simplified
>> anyway, fold the enumerator definitions with the (modified accordingly)
>> KMAP_D() macro always.
>> 
>> The whole point of the reduction is that, at least on ix86, the number of
>> kmap types can (depending on configuration) affect the amount of low
>> memory, and thus unused types should be avoided if possible.
> 
> Feh, its only a few pages and since there is no way to actually tell if
> you've got enough kmap atomic pages other than experiencing runtime
> errors, removing them must be done with utmost prudence.

Whether 2Mb of lowmem is "only a few pages" certainly depends
on the perspective you take.

And even then - shouldn't the bad (non-enumerated) uses of
atomic kmap-s be fixed rather than keeping unused entries in
the enumeration just because there is broken code somewhere?

Jan

Re: + kmap-types-clean-up-and-optimization.patch added to -mm tree

[Peter Zijlstra]

On Thu, 2010-12-23 at 10:47 +0000, Jan Beulich wrote:
> >>> On 23.12.10 at 10:58, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > On Wed, 2010-12-22 at 14:48 -0800, akpm@linux-foundation.org wrote:
> >> The patch titled
> >>      kmap-types: clean up and optimization
> >> has been added to the -mm tree.  Its filename is
> >>      kmap-types-clean-up-and-optimization.patch
> >> 
> >> Before you just go and hit "reply", please:
> >>    a) Consider who else should be cc'ed
> >>    b) Prefer to cc a suitable mailing list as well
> >>    c) Ideally: find the original patch on the mailing list and do a
> >>       reply-to-all to that, adding suitable additional cc's
> >> 
> > 
> >> ------------------------------------------------------
> >> Subject: kmap-types: clean up and optimization
> >> From: "Jan Beulich" <JBeulich@novell.com>
> >> 
> >> Several of the types aren't being used at all anymore - those can be
> >> deleted altogether.  
> > 
> > NO! That's wrong, in fact non of them are being used, but removing them
> > will decrease the number of kmap_atomic slots, but those are still being
> > used.
> 
> Would you mind pointing out examples of such uses (i.e. without
> the proper enumerator)? How would those avoid collisions with
> actually used slots?

Nobody uses explicit slots anymore:

/*
 * Make both: kmap_atomic(page, idx) and kmap_atomic(page) work.
 */
#define kmap_atomic(page, args...) __kmap_atomic(page)

All instances of KM_foo are deprecated and in need of a cleanup.
See commit: 3e4d3af501cccdc8a8cca41bdbe57d54ad7e7e73

> > Feh, its only a few pages and since there is no way to actually tell if
> > you've got enough kmap atomic pages other than experiencing runtime
> > errors, removing them must be done with utmost prudence.
> 
> Whether 2Mb of lowmem is "only a few pages" certainly depends
> on the perspective you take.
> 
> And even then - shouldn't the bad (non-enumerated) uses of
> atomic kmap-s be fixed rather than keeping unused entries in
> the enumeration just because there is broken code somewhere?

With the current 20 slots on x86, its 80k per CPU, you need 25 CPUs to
cross the 2M boundary, 32bit kernels having that many CPUs deserve to
suffer.