* [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing
[not found] ` <20180712172942.10094-3-hannes@cmpxchg.org>
@ 2018-07-23 13:36 ` Arnd Bergmann
2018-07-23 15:23 ` Johannes Weiner
0 siblings, 1 reply; 6+ messages in thread
From: Arnd Bergmann @ 2018-07-23 13:36 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jul 12, 2018 at 7:29 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> How many page->flags does this leave us with on 32-bit?
>
> 20 bits are always page flags
>
> 21 if you have an MMU
>
> 23 with the zone bits for DMA, Normal, HighMem, Movable
>
> 29 with the sparsemem section bits
>
> 30 if PAE is enabled
>
> 31 with this patch.
>
> So on 32-bit PAE, that leaves 1 bit for distinguishing two NUMA
> nodes. If that's not enough, the system can switch to discontigmem and
> re-gain the 6 or 7 sparsemem section bits.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
It seems we ran out of bits on arm64 in randconfig builds:
In file included from /git/arm-soc/include/linux/kernel.h:10,
from /git/arm-soc/arch/arm64/mm/init.c:20:
/git/arm-soc/arch/arm64/mm/init.c: In function 'mem_init':
/git/arm-soc/include/linux/compiler.h:357:38: error: call to
'__compiletime_assert_618' declared with attribute error: BUILD_BUG_ON
failed: sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
/git/arm-soc/include/linux/compiler.h:337:4: note: in definition of
macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
/git/arm-soc/include/linux/compiler.h:357:2: note: in expansion of
macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
/git/arm-soc/include/linux/build_bug.h:45:37: note: in expansion of
macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
/git/arm-soc/include/linux/build_bug.h:69:2: note: in expansion of
macro 'BUILD_BUG_ON_MSG'
BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
^~~~~~~~~~~~~~~~
/git/arm-soc/arch/arm64/mm/init.c:618:2: note: in expansion of macro
'BUILD_BUG_ON'
BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
^~~~~~~~~~~~
/git/arm-soc/scripts/Makefile.build:317: recipe for target
'arch/arm64/mm/init.o' failed
Apparently this triggered
#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <=
BITS_PER_LONG - NR_PAGEFLAGS
#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
#else
#define LAST_CPUPID_WIDTH 0
#endif
and in turn
#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
#endif
and that _last_cpupid in struct page made sizeof(struct page) larger than 64.
This is for a randconfig build, see https://pastebin.com/YuwSTah3
for the configuration file, some of the relevant options are
CONFIG_64BIT=y
CONFIG_MEMCG=y
CONFIG_SPARSEMEM=y
CONFIG_ARM64_PA_BITS=52
CONFIG_ARM64_64K_PAGES=y
CONFIG_NR_CPUS=64
CONFIG_NUMA_BALANCING=y
# CONFIG_SPARSEMEM_VMEMMAP is not set
CONFIG_NODES_SHIFT=2
# CONFIG_ARCH_USES_PG_UNCACHED is not set
CONFIG_MEMORY_FAILURE=y
CONFIG_IDLE_PAGE_TRACKING=y
#define MAX_NR_ZONES 3
#define ZONES_SHIFT 2
#define MAX_PHYSMEM_BITS 52
#define SECTION_SIZE_BITS 30
#define SECTIONS_WIDTH 22
#define ZONES_WIDTH 2
#define NODES_SHIFT 2
#define LAST__PID_SHIFT 8
#define NR_CPUS_BITS 6
#define LAST_CPUPID_SHIFT 14
#define NR_PAGEFLAGS 25
With the extra page flag, the sum of SECTIONS_WIDTH, NODES_SHIFT, ZONES_WIDTH,
LAST_CPUPID_SHIFT, and NR_PAGEFLAGS is now 65. Before this change, I could
not trigger that error in randconfig builds. However, setting CONFIG_NR_CPUS or
CONFIG_NODES_SHIFT higher than the defaults would trigger it as well (randconfig
does not randomize those options).
Arnd
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing
2018-07-23 13:36 ` [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing Arnd Bergmann
@ 2018-07-23 15:23 ` Johannes Weiner
2018-07-23 15:35 ` Arnd Bergmann
0 siblings, 1 reply; 6+ messages in thread
From: Johannes Weiner @ 2018-07-23 15:23 UTC (permalink / raw)
To: linux-arm-kernel
Hi Arnd,
On Mon, Jul 23, 2018 at 03:36:09PM +0200, Arnd Bergmann wrote:
> On Thu, Jul 12, 2018 at 7:29 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> > How many page->flags does this leave us with on 32-bit?
> >
> > 20 bits are always page flags
> >
> > 21 if you have an MMU
> >
> > 23 with the zone bits for DMA, Normal, HighMem, Movable
> >
> > 29 with the sparsemem section bits
> >
> > 30 if PAE is enabled
> >
> > 31 with this patch.
> >
> > So on 32-bit PAE, that leaves 1 bit for distinguishing two NUMA
> > nodes. If that's not enough, the system can switch to discontigmem and
> > re-gain the 6 or 7 sparsemem section bits.
> >
> > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
>
> It seems we ran out of bits on arm64 in randconfig builds:
>
> In file included from /git/arm-soc/include/linux/kernel.h:10,
> from /git/arm-soc/arch/arm64/mm/init.c:20:
> /git/arm-soc/arch/arm64/mm/init.c: In function 'mem_init':
> /git/arm-soc/include/linux/compiler.h:357:38: error: call to
> '__compiletime_assert_618' declared with attribute error: BUILD_BUG_ON
> failed: sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)
This BUILD_BUG_ON() is to make sure we're sizing the VMEMMAP struct
page array properly (address space divided by struct page size).
>From the code:
/*
* Log2 of the upper bound of the size of a struct page. Used for sizing
* the vmemmap region only, does not affect actual memory footprint.
* We don't use sizeof(struct page) directly since taking its size here
* requires its definition to be available at this point in the inclusion
* chain, and it may not be a power of 2 in the first place.
*/
#define STRUCT_PAGE_MAX_SHIFT 6
> Apparently this triggered
>
> #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <=
> BITS_PER_LONG - NR_PAGEFLAGS
> #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
> #else
> #define LAST_CPUPID_WIDTH 0
> #endif
>
> and in turn
>
> #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
> #define LAST_CPUPID_NOT_IN_PAGE_FLAGS
> #endif
>
> and that _last_cpupid in struct page made sizeof(struct page) larger than 64.
>
> This is for a randconfig build, see https://pastebin.com/YuwSTah3
> for the configuration file, some of the relevant options are
>
> CONFIG_64BIT=y
> CONFIG_MEMCG=y
> CONFIG_SPARSEMEM=y
> CONFIG_ARM64_PA_BITS=52
> CONFIG_ARM64_64K_PAGES=y
> CONFIG_NR_CPUS=64
> CONFIG_NUMA_BALANCING=y
> # CONFIG_SPARSEMEM_VMEMMAP is not set
However, the check isn't conditional on that config option. And when
VMEMMAP is disabled, we need 22 additional bits to identify the sparse
memory sections in page->flags as well:
> CONFIG_NODES_SHIFT=2
> # CONFIG_ARCH_USES_PG_UNCACHED is not set
> CONFIG_MEMORY_FAILURE=y
> CONFIG_IDLE_PAGE_TRACKING=y
>
> #define MAX_NR_ZONES 3
> #define ZONES_SHIFT 2
> #define MAX_PHYSMEM_BITS 52
> #define SECTION_SIZE_BITS 30
> #define SECTIONS_WIDTH 22
^^^ Those we get back with VMEMMAP enabled.
So for configs for which the check is intended, it passes. We just
need to make it conditional to those.
---
>From 1d24635a6c7cd395bad5c29a3b9e5d2e98d9ab84 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 23 Jul 2018 10:18:23 -0400
Subject: [PATCH] arm64: fix vmemmap BUILD_BUG_ON() triggering on !vmemmap
setups
Arnd reports the following arm64 randconfig build error with the PSI
patches that add another page flag:
/git/arm-soc/arch/arm64/mm/init.c: In function 'mem_init':
/git/arm-soc/include/linux/compiler.h:357:38: error: call to
'__compiletime_assert_618' declared with attribute error: BUILD_BUG_ON
failed: sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)
The additional page flag causes other information stored in
page->flags to get bumped into their own struct page member:
#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <=
BITS_PER_LONG - NR_PAGEFLAGS
#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
#else
#define LAST_CPUPID_WIDTH 0
#endif
#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
#endif
which in turn causes the struct page size to exceed the size set in
STRUCT_PAGE_MAX_SHIFT. This value is an an estimate used to size the
VMEMMAP page array according to address space and struct page size.
However, the check is performed - and triggers here - on a !VMEMMAP
config, which consumes an additional 22 page bits for the sparse
section id. When VMEMMAP is enabled, those bits are returned, cpupid
doesn't need its own member, and the page passes the VMEMMAP check.
Restrict that check to the situation it was meant to check: that we
are sizing the VMEMMAP page array correctly.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
arch/arm64/mm/init.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 1b18b4722420..72c9b6778b0a 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -611,11 +611,13 @@ void __init mem_init(void)
BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
#endif
+#ifndef CONFIG_SPARSEMEM_VMEMMAP
/*
* Make sure we chose the upper bound of sizeof(struct page)
- * correctly.
+ * correctly when sizing the VMEMMAP array.
*/
BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
+#endif
if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
extern int sysctl_overcommit_memory;
--
2.18.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing
2018-07-23 15:23 ` Johannes Weiner
@ 2018-07-23 15:35 ` Arnd Bergmann
2018-07-23 16:27 ` Johannes Weiner
0 siblings, 1 reply; 6+ messages in thread
From: Arnd Bergmann @ 2018-07-23 15:35 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Jul 23, 2018 at 5:23 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Mon, Jul 23, 2018 at 03:36:09PM +0200, Arnd Bergmann wrote:
>> On Thu, Jul 12, 2018 at 7:29 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
>> In file included from /git/arm-soc/include/linux/kernel.h:10,
>> from /git/arm-soc/arch/arm64/mm/init.c:20:
>> /git/arm-soc/arch/arm64/mm/init.c: In function 'mem_init':
>> /git/arm-soc/include/linux/compiler.h:357:38: error: call to
>> '__compiletime_assert_618' declared with attribute error: BUILD_BUG_ON
>> failed: sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)
>
> This BUILD_BUG_ON() is to make sure we're sizing the VMEMMAP struct
> page array properly (address space divided by struct page size).
>
> From the code:
>
> /*
> * Log2 of the upper bound of the size of a struct page. Used for sizing
> * the vmemmap region only, does not affect actual memory footprint.
> * We don't use sizeof(struct page) directly since taking its size here
> * requires its definition to be available at this point in the inclusion
> * chain, and it may not be a power of 2 in the first place.
> */
> #define STRUCT_PAGE_MAX_SHIFT 6
>
...
> However, the check isn't conditional on that config option. And when
> VMEMMAP is disabled, we need 22 additional bits to identify the sparse
> memory sections in page->flags as well:
>
>> CONFIG_NODES_SHIFT=2
>> # CONFIG_ARCH_USES_PG_UNCACHED is not set
>> CONFIG_MEMORY_FAILURE=y
>> CONFIG_IDLE_PAGE_TRACKING=y
>>
>> #define MAX_NR_ZONES 3
>> #define ZONES_SHIFT 2
>> #define MAX_PHYSMEM_BITS 52
>> #define SECTION_SIZE_BITS 30
>> #define SECTIONS_WIDTH 22
>
> ^^^ Those we get back with VMEMMAP enabled.
>
> So for configs for which the check is intended, it passes. We just
> need to make it conditional to those.
Ok, thanks for the analysis, I had missed that and was about to
send a different patch to increase STRUCT_PAGE_MAX_SHIFT
in some configurations, which is not as good.
> From 1d24635a6c7cd395bad5c29a3b9e5d2e98d9ab84 Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@cmpxchg.org>
> Date: Mon, 23 Jul 2018 10:18:23 -0400
> Subject: [PATCH] arm64: fix vmemmap BUILD_BUG_ON() triggering on !vmemmap
> setups
>
> Arnd reports the following arm64 randconfig build error with the PSI
> patches that add another page flag:
>
You could add further text here that I had just added to my
patch description (not sent):
Further experiments show that the build error already existed before,
but was only triggered with larger values of CONFIG_NR_CPU and/or
CONFIG_NODES_SHIFT that might be used in actual configurations but
not in randconfig builds.
With longer CPU and node masks, I could recreate the problem with
kernels as old as linux-4.7 when arm64 NUMA support got added.
Cc: stable at vger.kernel.org
Fixes: 1a2db300348b ("arm64, numa: Add NUMA support for arm64 platforms.")
Fixes: 3e1907d5bf5a ("arm64: mm: move vmemmap region right below
the linear region")
> arch/arm64/mm/init.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 1b18b4722420..72c9b6778b0a 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -611,11 +611,13 @@ void __init mem_init(void)
> BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
> #endif
>
> +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> /*
I tested it on two broken configurations, and found that you have
a typo here, it should be 'ifdef', not 'ifndef'. With that change, it
seems to build fine.
Tested-by: Arnd Bergmann <arnd@arndb.de>
Arnd
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing
2018-07-23 15:35 ` Arnd Bergmann
@ 2018-07-23 16:27 ` Johannes Weiner
2018-07-24 15:04 ` Will Deacon
0 siblings, 1 reply; 6+ messages in thread
From: Johannes Weiner @ 2018-07-23 16:27 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Jul 23, 2018 at 05:35:35PM +0200, Arnd Bergmann wrote:
> On Mon, Jul 23, 2018 at 5:23 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> > From 1d24635a6c7cd395bad5c29a3b9e5d2e98d9ab84 Mon Sep 17 00:00:00 2001
> > From: Johannes Weiner <hannes@cmpxchg.org>
> > Date: Mon, 23 Jul 2018 10:18:23 -0400
> > Subject: [PATCH] arm64: fix vmemmap BUILD_BUG_ON() triggering on !vmemmap
> > setups
> >
> > Arnd reports the following arm64 randconfig build error with the PSI
> > patches that add another page flag:
> >
>
> You could add further text here that I had just added to my
> patch description (not sent):
>
> Further experiments show that the build error already existed before,
> but was only triggered with larger values of CONFIG_NR_CPU and/or
> CONFIG_NODES_SHIFT that might be used in actual configurations but
> not in randconfig builds.
>
> With longer CPU and node masks, I could recreate the problem with
> kernels as old as linux-4.7 when arm64 NUMA support got added.
>
> Cc: stable at vger.kernel.org
> Fixes: 1a2db300348b ("arm64, numa: Add NUMA support for arm64 platforms.")
> Fixes: 3e1907d5bf5a ("arm64: mm: move vmemmap region right below
> the linear region")
Sure thing.
> > arch/arm64/mm/init.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 1b18b4722420..72c9b6778b0a 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -611,11 +611,13 @@ void __init mem_init(void)
> > BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
> > #endif
> >
> > +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> > /*
>
> I tested it on two broken configurations, and found that you have
> a typo here, it should be 'ifdef', not 'ifndef'. With that change, it
> seems to build fine.
>
> Tested-by: Arnd Bergmann <arnd@arndb.de>
Thanks for testing it, I don't have a cross-compile toolchain set up.
---
>From 34c4c4549f09f971d2d391a8d652d56cb9b05475 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 23 Jul 2018 10:18:23 -0400
Subject: [PATCH] arm64: fix vmemmap BUILD_BUG_ON() triggering on !vmemmap
setups
Arnd reports the following arm64 randconfig build error with the PSI
patches that add another page flag:
/git/arm-soc/arch/arm64/mm/init.c: In function 'mem_init':
/git/arm-soc/include/linux/compiler.h:357:38: error: call to
'__compiletime_assert_618' declared with attribute error: BUILD_BUG_ON
failed: sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)
The additional page flag causes other information stored in
page->flags to get bumped into their own struct page member:
#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <=
BITS_PER_LONG - NR_PAGEFLAGS
#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
#else
#define LAST_CPUPID_WIDTH 0
#endif
#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
#endif
which in turn causes the struct page size to exceed the size set in
STRUCT_PAGE_MAX_SHIFT. This value is an an estimate used to size the
VMEMMAP page array according to address space and struct page size.
However, the check is performed - and triggers here - on a !VMEMMAP
config, which consumes an additional 22 page bits for the sparse
section id. When VMEMMAP is enabled, those bits are returned, cpupid
doesn't need its own member, and the page passes the VMEMMAP check.
Restrict that check to the situation it was meant to check: that we
are sizing the VMEMMAP page array correctly.
Says Arnd:
Further experiments show that the build error already existed before,
but was only triggered with larger values of CONFIG_NR_CPU and/or
CONFIG_NODES_SHIFT that might be used in actual configurations but
not in randconfig builds.
With longer CPU and node masks, I could recreate the problem with
kernels as old as linux-4.7 when arm64 NUMA support got added.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Cc: stable at vger.kernel.org
Fixes: 1a2db300348b ("arm64, numa: Add NUMA support for arm64 platforms.")
Fixes: 3e1907d5bf5a ("arm64: mm: move vmemmap region right below the linear region")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
arch/arm64/mm/init.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 1b18b4722420..86d9f9d303b0 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -611,11 +611,13 @@ void __init mem_init(void)
BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
#endif
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
/*
* Make sure we chose the upper bound of sizeof(struct page)
- * correctly.
+ * correctly when sizing the VMEMMAP array.
*/
BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
+#endif
if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
extern int sysctl_overcommit_memory;
--
2.18.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing
2018-07-23 16:27 ` Johannes Weiner
@ 2018-07-24 15:04 ` Will Deacon
2018-07-25 16:06 ` Will Deacon
0 siblings, 1 reply; 6+ messages in thread
From: Will Deacon @ 2018-07-24 15:04 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Jul 23, 2018 at 12:27:35PM -0400, Johannes Weiner wrote:
> On Mon, Jul 23, 2018 at 05:35:35PM +0200, Arnd Bergmann wrote:
> > On Mon, Jul 23, 2018 at 5:23 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > > index 1b18b4722420..72c9b6778b0a 100644
> > > --- a/arch/arm64/mm/init.c
> > > +++ b/arch/arm64/mm/init.c
> > > @@ -611,11 +611,13 @@ void __init mem_init(void)
> > > BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
> > > #endif
> > >
> > > +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> > > /*
> >
> > I tested it on two broken configurations, and found that you have
> > a typo here, it should be 'ifdef', not 'ifndef'. With that change, it
> > seems to build fine.
> >
> > Tested-by: Arnd Bergmann <arnd@arndb.de>
>
> Thanks for testing it, I don't have a cross-compile toolchain set up.
>
> ---
Thanks Arnd, Johannes. I can pick this up for -rc7 via the arm64 tree,
unless it's already queued elsewhere?
Will
> From 34c4c4549f09f971d2d391a8d652d56cb9b05475 Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@cmpxchg.org>
> Date: Mon, 23 Jul 2018 10:18:23 -0400
> Subject: [PATCH] arm64: fix vmemmap BUILD_BUG_ON() triggering on !vmemmap
> setups
>
> Arnd reports the following arm64 randconfig build error with the PSI
> patches that add another page flag:
>
> /git/arm-soc/arch/arm64/mm/init.c: In function 'mem_init':
> /git/arm-soc/include/linux/compiler.h:357:38: error: call to
> '__compiletime_assert_618' declared with attribute error: BUILD_BUG_ON
> failed: sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)
>
> The additional page flag causes other information stored in
> page->flags to get bumped into their own struct page member:
>
> #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <=
> BITS_PER_LONG - NR_PAGEFLAGS
> #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
> #else
> #define LAST_CPUPID_WIDTH 0
> #endif
>
> #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
> #define LAST_CPUPID_NOT_IN_PAGE_FLAGS
> #endif
>
> which in turn causes the struct page size to exceed the size set in
> STRUCT_PAGE_MAX_SHIFT. This value is an an estimate used to size the
> VMEMMAP page array according to address space and struct page size.
>
> However, the check is performed - and triggers here - on a !VMEMMAP
> config, which consumes an additional 22 page bits for the sparse
> section id. When VMEMMAP is enabled, those bits are returned, cpupid
> doesn't need its own member, and the page passes the VMEMMAP check.
>
> Restrict that check to the situation it was meant to check: that we
> are sizing the VMEMMAP page array correctly.
>
> Says Arnd:
>
> Further experiments show that the build error already existed before,
> but was only triggered with larger values of CONFIG_NR_CPU and/or
> CONFIG_NODES_SHIFT that might be used in actual configurations but
> not in randconfig builds.
>
> With longer CPU and node masks, I could recreate the problem with
> kernels as old as linux-4.7 when arm64 NUMA support got added.
>
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Tested-by: Arnd Bergmann <arnd@arndb.de>
> Cc: stable at vger.kernel.org
> Fixes: 1a2db300348b ("arm64, numa: Add NUMA support for arm64 platforms.")
> Fixes: 3e1907d5bf5a ("arm64: mm: move vmemmap region right below the linear region")
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> ---
> arch/arm64/mm/init.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 1b18b4722420..86d9f9d303b0 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -611,11 +611,13 @@ void __init mem_init(void)
> BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
> #endif
>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> /*
> * Make sure we chose the upper bound of sizeof(struct page)
> - * correctly.
> + * correctly when sizing the VMEMMAP array.
> */
> BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
> +#endif
>
> if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
> extern int sysctl_overcommit_memory;
> --
> 2.18.0
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing
2018-07-24 15:04 ` Will Deacon
@ 2018-07-25 16:06 ` Will Deacon
0 siblings, 0 replies; 6+ messages in thread
From: Will Deacon @ 2018-07-25 16:06 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Jul 24, 2018 at 04:04:48PM +0100, Will Deacon wrote:
> On Mon, Jul 23, 2018 at 12:27:35PM -0400, Johannes Weiner wrote:
> > On Mon, Jul 23, 2018 at 05:35:35PM +0200, Arnd Bergmann wrote:
> > > On Mon, Jul 23, 2018 at 5:23 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> > > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > > > index 1b18b4722420..72c9b6778b0a 100644
> > > > --- a/arch/arm64/mm/init.c
> > > > +++ b/arch/arm64/mm/init.c
> > > > @@ -611,11 +611,13 @@ void __init mem_init(void)
> > > > BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
> > > > #endif
> > > >
> > > > +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> > > > /*
> > >
> > > I tested it on two broken configurations, and found that you have
> > > a typo here, it should be 'ifdef', not 'ifndef'. With that change, it
> > > seems to build fine.
> > >
> > > Tested-by: Arnd Bergmann <arnd@arndb.de>
> >
> > Thanks for testing it, I don't have a cross-compile toolchain set up.
> >
> > ---
>
> Thanks Arnd, Johannes. I can pick this up for -rc7 via the arm64 tree,
> unless it's already queued elsewhere?
I've pushed this to the arm64 for-next/fixes branch heading for -rc7.
Will
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-07-25 16:06 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2018-07-23 13:36 ` [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing Arnd Bergmann
2018-07-23 15:23 ` Johannes Weiner
2018-07-23 15:35 ` Arnd Bergmann
2018-07-23 16:27 ` Johannes Weiner
2018-07-24 15:04 ` Will Deacon
2018-07-25 16:06 ` Will Deacon
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