* [PATCH] smaps: Report correct page sizes with THP
@ 2026-02-09 20:17 Andi Kleen
2026-02-12 12:42 ` David Hildenbrand (Arm)
2026-02-21 0:03 ` jane.chu
0 siblings, 2 replies; 10+ messages in thread
From: Andi Kleen @ 2026-02-09 20:17 UTC (permalink / raw)
To: linux-mm; +Cc: linux-fsdevel, akpm, willy, Andi Kleen
Recently I wasted quite some time debugging why THP didn't work, when it
was just smaps always reporting the base page size. It has separate
counts for (non m) THP, but using them is not always obvious. For
standard THP the page sizes can be actually derived from the existing
counts, so do just do that. I left KernelPageSize alone.
The mixed page size case is reported with a new MMUPageSize2 item.
This doesn't do anything about mTHP reporting, but even the basic
smaps is not aware of it so far.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
Documentation/filesystems/proc.rst | 2 +-
fs/proc/task_mmu.c | 14 +++++++++++++-
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 8256e857e2d7..7c776046d15a 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -483,7 +483,7 @@ entries; the page size used by the MMU when backing a VMA (in most cases,
the same as KernelPageSize); the amount of the mapping that is currently
resident in RAM (RSS); the process's proportional share of this mapping
(PSS); and the number of clean and dirty shared and private pages in the
-mapping.
+mapping. If the mapping has multiple page size there might be a MMUPageSize2.
The "proportional set size" (PSS) of a process is the count of pages it has
in memory, where each page is divided by the number of processes sharing it.
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 26188a4ad1ab..9123e59dcf4c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1377,7 +1377,19 @@ static int show_smap(struct seq_file *m, void *v)
SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
- SEQ_PUT_DEC(" kB\nMMUPageSize: ", vma_mmu_pagesize(vma));
+
+ /* Only THP? */
+ if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp == mss.resident &&
+ mss.resident > 0) {
+ SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
+ } else {
+ unsigned ps = vma_mmu_pagesize(vma);
+ /* Will need adjustments when more THP page sizes are added. */
+ SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
+ if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
+ ps != HPAGE_PMD_SIZE)
+ SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
+ }
seq_puts(m, " kB\n");
__show_smap(m, &mss, false);
--
2.52.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH] smaps: Report correct page sizes with THP
2026-02-09 20:17 [PATCH] smaps: Report correct page sizes with THP Andi Kleen
@ 2026-02-12 12:42 ` David Hildenbrand (Arm)
2026-02-12 17:58 ` Andi Kleen
2026-02-21 0:03 ` jane.chu
1 sibling, 1 reply; 10+ messages in thread
From: David Hildenbrand (Arm) @ 2026-02-12 12:42 UTC (permalink / raw)
To: Andi Kleen, linux-mm; +Cc: linux-fsdevel, akpm, willy
On 2/9/26 21:17, Andi Kleen wrote:
> Recently I wasted quite some time debugging why THP didn't work, when it
> was just smaps always reporting the base page size. It has separate
> counts for (non m) THP, but using them is not always obvious. For
> standard THP the page sizes can be actually derived from the existing
> counts, so do just do that. I left KernelPageSize alone.
> The mixed page size case is reported with a new MMUPageSize2 item.
> This doesn't do anything about mTHP reporting, but even the basic
> smaps is not aware of it so far.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> Documentation/filesystems/proc.rst | 2 +-
> fs/proc/task_mmu.c | 14 +++++++++++++-
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 8256e857e2d7..7c776046d15a 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -483,7 +483,7 @@ entries; the page size used by the MMU when backing a VMA (in most cases,
> the same as KernelPageSize); the amount of the mapping that is currently
> resident in RAM (RSS); the process's proportional share of this mapping
> (PSS); and the number of clean and dirty shared and private pages in the
> -mapping.
> +mapping. If the mapping has multiple page size there might be a MMUPageSize2.
>
> The "proportional set size" (PSS) of a process is the count of pages it has
> in memory, where each page is divided by the number of processes sharing it.
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 26188a4ad1ab..9123e59dcf4c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1377,7 +1377,19 @@ static int show_smap(struct seq_file *m, void *v)
>
> SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
> SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
> - SEQ_PUT_DEC(" kB\nMMUPageSize: ", vma_mmu_pagesize(vma));
> +
> + /* Only THP? */
> + if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp == mss.resident &&
> + mss.resident > 0) {
> + SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
> + } else {
> + unsigned ps = vma_mmu_pagesize(vma);
> + /* Will need adjustments when more THP page sizes are added. */
> + SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
> + if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
> + ps != HPAGE_PMD_SIZE)
> + SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
> + }
> seq_puts(m, " kB\n");
>
> __show_smap(m, &mss, false);
We have AnonHugePages:, ShmemPmdMapped: and FilePmdMapped: that tell you
exactly what you want to know.
Especially the mixed thing is just nasty.
Once we go into cont-pte territory (or automatic pte coalescing by
hardware) it all gets confusing.
Sorry, NAK.
--
Cheers,
David
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] smaps: Report correct page sizes with THP
2026-02-12 12:42 ` David Hildenbrand (Arm)
@ 2026-02-12 17:58 ` Andi Kleen
2026-02-12 18:05 ` David Hildenbrand (Arm)
0 siblings, 1 reply; 10+ messages in thread
From: Andi Kleen @ 2026-02-12 17:58 UTC (permalink / raw)
To: David Hildenbrand (Arm); +Cc: linux-mm, linux-fsdevel, akpm, willy
> We have AnonHugePages:, ShmemPmdMapped: and FilePmdMapped: that tell you
> exactly what you want to know.
.... if you know about it. I personally wasted a lot of time on it
because we trusted a lie.
>
> Especially the mixed thing is just nasty.
>
> Once we go into cont-pte territory (or automatic pte coalescing by hardware)
> it all gets confusing.
In this case it can be extended to more.
>
> Sorry, NAK.
Okay then just remove the page size if it's fictional outside hugetlb anyways?
I can send that patch too, but it would seem inferior.
-Andi
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] smaps: Report correct page sizes with THP
2026-02-12 17:58 ` Andi Kleen
@ 2026-02-12 18:05 ` David Hildenbrand (Arm)
0 siblings, 0 replies; 10+ messages in thread
From: David Hildenbrand (Arm) @ 2026-02-12 18:05 UTC (permalink / raw)
To: Andi Kleen; +Cc: linux-mm, linux-fsdevel, akpm, willy
On 2/12/26 18:58, Andi Kleen wrote:
>> We have AnonHugePages:, ShmemPmdMapped: and FilePmdMapped: that tell you
>> exactly what you want to know.
>
> .... if you know about it. I personally wasted a lot of time on it
> because we trusted a lie.
It is confusing, I agree. I don't know why we added it in the first place.
>
>>
>> Especially the mixed thing is just nasty.
>>
>> Once we go into cont-pte territory (or automatic pte coalescing by hardware)
>> it all gets confusing.
>
> In this case it can be extended to more.
>
>>
>> Sorry, NAK.
>
> Okay then just remove the page size if it's fictional outside hugetlb anyways?
I'm sure that would break some tooling.
--
Cheers,
David
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] smaps: Report correct page sizes with THP
2026-02-09 20:17 [PATCH] smaps: Report correct page sizes with THP Andi Kleen
2026-02-12 12:42 ` David Hildenbrand (Arm)
@ 2026-02-21 0:03 ` jane.chu
1 sibling, 0 replies; 10+ messages in thread
From: jane.chu @ 2026-02-21 0:03 UTC (permalink / raw)
To: Andi Kleen, linux-mm; +Cc: linux-fsdevel, akpm, willy
On 2/9/2026 12:17 PM, Andi Kleen wrote:
> Recently I wasted quite some time debugging why THP didn't work, when it
> was just smaps always reporting the base page size. It has separate
> counts for (non m) THP, but using them is not always obvious. For
> standard THP the page sizes can be actually derived from the existing
> counts, so do just do that. I left KernelPageSize alone.
> The mixed page size case is reported with a new MMUPageSize2 item.
> This doesn't do anything about mTHP reporting, but even the basic
> smaps is not aware of it so far.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> Documentation/filesystems/proc.rst | 2 +-
> fs/proc/task_mmu.c | 14 +++++++++++++-
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 8256e857e2d7..7c776046d15a 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -483,7 +483,7 @@ entries; the page size used by the MMU when backing a VMA (in most cases,
> the same as KernelPageSize); the amount of the mapping that is currently
> resident in RAM (RSS); the process's proportional share of this mapping
> (PSS); and the number of clean and dirty shared and private pages in the
> -mapping.
> +mapping. If the mapping has multiple page size there might be a MMUPageSize2.
>
> The "proportional set size" (PSS) of a process is the count of pages it has
> in memory, where each page is divided by the number of processes sharing it.
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 26188a4ad1ab..9123e59dcf4c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1377,7 +1377,19 @@ static int show_smap(struct seq_file *m, void *v)
>
> SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
> SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
> - SEQ_PUT_DEC(" kB\nMMUPageSize: ", vma_mmu_pagesize(vma));
> +
> + /* Only THP? */
> + if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp == mss.resident &&
> + mss.resident > 0) {
> + SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
> + } else {
> + unsigned ps = vma_mmu_pagesize(vma);
> + /* Will need adjustments when more THP page sizes are added. */
> + SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
> + if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
> + ps != HPAGE_PMD_SIZE)
> + SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
> + }
> seq_puts(m, " kB\n");
>
> __show_smap(m, &mss, false);
Looks good to me.
While you're at this, maybe you could remove the redundant entries in
the documentation?
452 Size: 1084 kB
453 KernelPageSize: 4 kB
454 MMUPageSize: 4 kB
455 Rss: 892 kB
456 Pss: 374 kB
[..]
472 KernelPageSize: 4 kB <--
473 MMUPageSize: 4 kB <--
Reviewed-by: Jane Chu <jane.chu@oracle.com>
thanks,
-jane
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] smaps: Report correct page sizes with THP
@ 2026-02-11 2:59 kernel test robot
0 siblings, 0 replies; 10+ messages in thread
From: kernel test robot @ 2026-02-11 2:59 UTC (permalink / raw)
To: oe-kbuild; +Cc: lkp
::::::
:::::: Manual check reason: "__compiletime_assert_NNN"
::::::
BCC: lkp@intel.com
CC: llvm@lists.linux.dev
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20260209201731.231667-1-ak@linux.intel.com>
References: <20260209201731.231667-1-ak@linux.intel.com>
TO: Andi Kleen <ak@linux.intel.com>
TO: linux-mm@kvack.org
CC: linux-fsdevel@vger.kernel.org
CC: akpm@linux-foundation.org
CC: willy@infradead.org
CC: Andi Kleen <ak@linux.intel.com>
Hi Andi,
kernel test robot noticed the following build errors:
[auto build test ERROR on brauner-vfs/vfs.all]
[also build test ERROR on linus/master v6.19 next-20260210]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Andi-Kleen/smaps-Report-correct-page-sizes-with-THP/20260210-042028
base: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.all
patch link: https://lore.kernel.org/r/20260209201731.231667-1-ak%40linux.intel.com
patch subject: [PATCH] smaps: Report correct page sizes with THP
:::::: branch date: 31 hours ago
:::::: commit date: 31 hours ago
config: x86_64-randconfig-015-20260210 (https://download.01.org/0day-ci/archive/20260211/202602111045.T7U5qnHV-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260211/202602111045.T7U5qnHV-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/r/202602111045.T7U5qnHV-lkp@intel.com/
All errors (new ones prefixed by >>):
>> fs/proc/task_mmu.c:1372:40: error: call to '__compiletime_assert_1237' declared with 'error' attribute: BUILD_BUG failed
1372 | SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
| ^
include/linux/huge_mm.h:120:34: note: expanded from macro 'HPAGE_PMD_SIZE'
120 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
| ^
include/linux/huge_mm.h:113:28: note: expanded from macro 'HPAGE_PMD_SHIFT'
113 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
| ^
include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
| ^
note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
include/linux/compiler_types.h:619:2: note: expanded from macro '_compiletime_assert'
619 | __compiletime_assert(condition, msg, prefix, suffix)
| ^
include/linux/compiler_types.h:612:4: note: expanded from macro '__compiletime_assert'
612 | prefix ## suffix(); \
| ^
<scratch space>:288:1: note: expanded from here
288 | __compiletime_assert_1237
| ^
fs/proc/task_mmu.c:1378:13: error: call to '__compiletime_assert_1238' declared with 'error' attribute: BUILD_BUG failed
1378 | ps != HPAGE_PMD_SIZE)
| ^
include/linux/huge_mm.h:120:34: note: expanded from macro 'HPAGE_PMD_SIZE'
120 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
| ^
include/linux/huge_mm.h:113:28: note: expanded from macro 'HPAGE_PMD_SHIFT'
113 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
| ^
include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
| ^
note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
include/linux/compiler_types.h:619:2: note: expanded from macro '_compiletime_assert'
619 | __compiletime_assert(condition, msg, prefix, suffix)
| ^
include/linux/compiler_types.h:612:4: note: expanded from macro '__compiletime_assert'
612 | prefix ## suffix(); \
| ^
<scratch space>:2:1: note: expanded from here
2 | __compiletime_assert_1238
| ^
2 errors generated.
vim +1372 fs/proc/task_mmu.c
f1547959d9efd0 Vlastimil Babka 2018-08-21 1356
8e68d689afe328 Vlastimil Babka 2018-08-21 1357 static int show_smap(struct seq_file *m, void *v)
8e68d689afe328 Vlastimil Babka 2018-08-21 1358 {
8e68d689afe328 Vlastimil Babka 2018-08-21 1359 struct vm_area_struct *vma = v;
860a2e7fa4a186 Alexey Dobriyan 2023-09-29 1360 struct mem_size_stats mss = {};
8e68d689afe328 Vlastimil Babka 2018-08-21 1361
03b4b1149308b0 Chinwen Chang 2020-10-13 1362 smap_gather_stats(vma, &mss, 0);
4752c369789250 Matt Mackall 2008-02-04 1363
871305bb202808 Vlastimil Babka 2018-08-21 1364 show_map_vma(m, vma);
4752c369789250 Matt Mackall 2008-02-04 1365
d1be35cb6f9697 Andrei Vagin 2018-04-10 1366 SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
d1be35cb6f9697 Andrei Vagin 2018-04-10 1367 SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
f9a5299667dd92 Andi Kleen 2026-02-09 1368
f9a5299667dd92 Andi Kleen 2026-02-09 1369 /* Only THP? */
f9a5299667dd92 Andi Kleen 2026-02-09 1370 if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp == mss.resident &&
f9a5299667dd92 Andi Kleen 2026-02-09 1371 mss.resident > 0) {
f9a5299667dd92 Andi Kleen 2026-02-09 @1372 SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
f9a5299667dd92 Andi Kleen 2026-02-09 1373 } else {
f9a5299667dd92 Andi Kleen 2026-02-09 1374 unsigned ps = vma_mmu_pagesize(vma);
f9a5299667dd92 Andi Kleen 2026-02-09 1375 /* Will need adjustments when more THP page sizes are added. */
f9a5299667dd92 Andi Kleen 2026-02-09 1376 SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
f9a5299667dd92 Andi Kleen 2026-02-09 1377 if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
f9a5299667dd92 Andi Kleen 2026-02-09 1378 ps != HPAGE_PMD_SIZE)
f9a5299667dd92 Andi Kleen 2026-02-09 1379 SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
f9a5299667dd92 Andi Kleen 2026-02-09 1380 }
d1be35cb6f9697 Andrei Vagin 2018-04-10 1381 seq_puts(m, " kB\n");
d1be35cb6f9697 Andrei Vagin 2018-04-10 1382
ee2ad71b0756e9 Luigi Semenzato 2019-07-11 1383 __show_smap(m, &mss, false);
f1547959d9efd0 Vlastimil Babka 2018-08-21 1384
daa60ae64c6587 Hugh Dickins 2023-08-14 1385 seq_printf(m, "THPeligible: %8u\n",
1f1c061089dcd2 David Hildenbrand 2025-08-15 1386 !!thp_vma_allowable_orders(vma, vma->vm_flags, TVA_SMAPS,
1f1c061089dcd2 David Hildenbrand 2025-08-15 1387 THP_ORDERS_ALL));
7635d9cbe8327e Michal Hocko 2018-12-28 1388
27cca866e3fce0 Ram Pai 2018-04-13 1389 if (arch_pkeys_enabled())
27cca866e3fce0 Ram Pai 2018-04-13 1390 seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma));
834f82e2aa9a8e Cyrill Gorcunov 2012-12-17 1391 show_smap_vma_flags(m, vma);
258f669e7e88c1 Vlastimil Babka 2018-08-21 1392
258f669e7e88c1 Vlastimil Babka 2018-08-21 1393 return 0;
258f669e7e88c1 Vlastimil Babka 2018-08-21 1394 }
258f669e7e88c1 Vlastimil Babka 2018-08-21 1395
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] smaps: Report correct page sizes with THP
@ 2026-02-09 21:31 kernel test robot
0 siblings, 0 replies; 10+ messages in thread
From: kernel test robot @ 2026-02-09 21:31 UTC (permalink / raw)
To: oe-kbuild; +Cc: lkp
::::::
:::::: Manual check reason: "__compiletime_assert_NNN"
::::::
BCC: lkp@intel.com
CC: llvm@lists.linux.dev
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20260209193223.230797-1-ak@linux.intel.com>
References: <20260209193223.230797-1-ak@linux.intel.com>
TO: Andi Kleen <ak@linux.intel.com>
TO: linux-mm@vger.kernel.org
CC: linux-fsdevel@vger.kernel.org
CC: akpm@linux-foundation.org
CC: Andi Kleen <ak@linux.intel.com>
Hi Andi,
kernel test robot noticed the following build errors:
[auto build test ERROR on brauner-vfs/vfs.all]
[also build test ERROR on linus/master v6.19 next-20260209]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Andi-Kleen/smaps-Report-correct-page-sizes-with-THP/20260210-033439
base: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.all
patch link: https://lore.kernel.org/r/20260209193223.230797-1-ak%40linux.intel.com
patch subject: [PATCH] smaps: Report correct page sizes with THP
:::::: branch date: 2 hours ago
:::::: commit date: 2 hours ago
config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20260210/202602100541.T3O4ksDH-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260210/202602100541.T3O4ksDH-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/r/202602100541.T3O4ksDH-lkp@intel.com/
All errors (new ones prefixed by >>):
>> fs/proc/task_mmu.c:1378:13: error: call to '__compiletime_assert_426' declared with 'error' attribute: BUILD_BUG failed
1378 | ps != HPAGE_PMD_SIZE)
| ^
include/linux/huge_mm.h:120:34: note: expanded from macro 'HPAGE_PMD_SIZE'
120 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
| ^
include/linux/huge_mm.h:113:28: note: expanded from macro 'HPAGE_PMD_SHIFT'
113 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
| ^
include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
| ^
note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
include/linux/compiler_types.h:619:2: note: expanded from macro '_compiletime_assert'
619 | __compiletime_assert(condition, msg, prefix, suffix)
| ^
include/linux/compiler_types.h:612:4: note: expanded from macro '__compiletime_assert'
612 | prefix ## suffix(); \
| ^
<scratch space>:129:1: note: expanded from here
129 | __compiletime_assert_426
| ^
fs/proc/task_mmu.c:1372:40: error: call to '__compiletime_assert_425' declared with 'error' attribute: BUILD_BUG failed
1372 | SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
| ^
include/linux/huge_mm.h:120:34: note: expanded from macro 'HPAGE_PMD_SIZE'
120 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
| ^
include/linux/huge_mm.h:113:28: note: expanded from macro 'HPAGE_PMD_SHIFT'
113 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
| ^
include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
| ^
note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
include/linux/compiler_types.h:619:2: note: expanded from macro '_compiletime_assert'
619 | __compiletime_assert(condition, msg, prefix, suffix)
| ^
include/linux/compiler_types.h:612:4: note: expanded from macro '__compiletime_assert'
612 | prefix ## suffix(); \
| ^
<scratch space>:126:1: note: expanded from here
126 | __compiletime_assert_425
| ^
2 errors generated.
vim +1378 fs/proc/task_mmu.c
f1547959d9efd0 Vlastimil Babka 2018-08-21 1356
8e68d689afe328 Vlastimil Babka 2018-08-21 1357 static int show_smap(struct seq_file *m, void *v)
8e68d689afe328 Vlastimil Babka 2018-08-21 1358 {
8e68d689afe328 Vlastimil Babka 2018-08-21 1359 struct vm_area_struct *vma = v;
860a2e7fa4a186 Alexey Dobriyan 2023-09-29 1360 struct mem_size_stats mss = {};
8e68d689afe328 Vlastimil Babka 2018-08-21 1361
03b4b1149308b0 Chinwen Chang 2020-10-13 1362 smap_gather_stats(vma, &mss, 0);
4752c369789250 Matt Mackall 2008-02-04 1363
871305bb202808 Vlastimil Babka 2018-08-21 1364 show_map_vma(m, vma);
4752c369789250 Matt Mackall 2008-02-04 1365
d1be35cb6f9697 Andrei Vagin 2018-04-10 1366 SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
d1be35cb6f9697 Andrei Vagin 2018-04-10 1367 SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
37b1c872e41df4 Andi Kleen 2026-02-09 1368
37b1c872e41df4 Andi Kleen 2026-02-09 1369 /* Only THP? */
37b1c872e41df4 Andi Kleen 2026-02-09 1370 if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp == mss.resident &&
37b1c872e41df4 Andi Kleen 2026-02-09 1371 mss.resident > 0) {
37b1c872e41df4 Andi Kleen 2026-02-09 1372 SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
37b1c872e41df4 Andi Kleen 2026-02-09 1373 } else {
37b1c872e41df4 Andi Kleen 2026-02-09 1374 unsigned ps = vma_mmu_pagesize(vma);
37b1c872e41df4 Andi Kleen 2026-02-09 1375 /* Will need adjustments when more THP page sizes are added. */
37b1c872e41df4 Andi Kleen 2026-02-09 1376 SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
37b1c872e41df4 Andi Kleen 2026-02-09 1377 if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
37b1c872e41df4 Andi Kleen 2026-02-09 @1378 ps != HPAGE_PMD_SIZE)
37b1c872e41df4 Andi Kleen 2026-02-09 1379 SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
37b1c872e41df4 Andi Kleen 2026-02-09 1380 }
d1be35cb6f9697 Andrei Vagin 2018-04-10 1381 seq_puts(m, " kB\n");
d1be35cb6f9697 Andrei Vagin 2018-04-10 1382
ee2ad71b0756e9 Luigi Semenzato 2019-07-11 1383 __show_smap(m, &mss, false);
f1547959d9efd0 Vlastimil Babka 2018-08-21 1384
daa60ae64c6587 Hugh Dickins 2023-08-14 1385 seq_printf(m, "THPeligible: %8u\n",
1f1c061089dcd2 David Hildenbrand 2025-08-15 1386 !!thp_vma_allowable_orders(vma, vma->vm_flags, TVA_SMAPS,
1f1c061089dcd2 David Hildenbrand 2025-08-15 1387 THP_ORDERS_ALL));
7635d9cbe8327e Michal Hocko 2018-12-28 1388
27cca866e3fce0 Ram Pai 2018-04-13 1389 if (arch_pkeys_enabled())
27cca866e3fce0 Ram Pai 2018-04-13 1390 seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma));
834f82e2aa9a8e Cyrill Gorcunov 2012-12-17 1391 show_smap_vma_flags(m, vma);
258f669e7e88c1 Vlastimil Babka 2018-08-21 1392
258f669e7e88c1 Vlastimil Babka 2018-08-21 1393 return 0;
258f669e7e88c1 Vlastimil Babka 2018-08-21 1394 }
258f669e7e88c1 Vlastimil Babka 2018-08-21 1395
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH] smaps: Report correct page sizes with THP
@ 2026-02-09 19:32 Andi Kleen
2026-02-09 20:04 ` Matthew Wilcox
0 siblings, 1 reply; 10+ messages in thread
From: Andi Kleen @ 2026-02-09 19:32 UTC (permalink / raw)
To: linux-mm; +Cc: linux-fsdevel, akpm, Andi Kleen
Recently I wasted quite some time debugging why THP didn't work, when it
was just smaps always reporting the base page size. It has separate
counts for (non m) THP, but using them is not always obvious. For
standard THP the page sizes can be actually derived from the existing
counts, so do just do that. I left KernelPageSize alone.
The mixed page size case is reported with a new MMUPageSize2 item.
This doesn't do anything about mTHP reporting, but even the basic
smaps is not aware of it so far.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
Documentation/filesystems/proc.rst | 2 +-
fs/proc/task_mmu.c | 14 +++++++++++++-
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 8256e857e2d7..7c776046d15a 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -483,7 +483,7 @@ entries; the page size used by the MMU when backing a VMA (in most cases,
the same as KernelPageSize); the amount of the mapping that is currently
resident in RAM (RSS); the process's proportional share of this mapping
(PSS); and the number of clean and dirty shared and private pages in the
-mapping.
+mapping. If the mapping has multiple page size there might be a MMUPageSize2.
The "proportional set size" (PSS) of a process is the count of pages it has
in memory, where each page is divided by the number of processes sharing it.
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 26188a4ad1ab..9123e59dcf4c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1377,7 +1377,19 @@ static int show_smap(struct seq_file *m, void *v)
SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
- SEQ_PUT_DEC(" kB\nMMUPageSize: ", vma_mmu_pagesize(vma));
+
+ /* Only THP? */
+ if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp == mss.resident &&
+ mss.resident > 0) {
+ SEQ_PUT_DEC(" kB\nMMUPageSize: ", HPAGE_PMD_SIZE);
+ } else {
+ unsigned ps = vma_mmu_pagesize(vma);
+ /* Will need adjustments when more THP page sizes are added. */
+ SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
+ if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
+ ps != HPAGE_PMD_SIZE)
+ SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
+ }
seq_puts(m, " kB\n");
__show_smap(m, &mss, false);
--
2.52.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH] smaps: Report correct page sizes with THP
2026-02-09 19:32 Andi Kleen
@ 2026-02-09 20:04 ` Matthew Wilcox
2026-02-09 20:10 ` Andi Kleen
0 siblings, 1 reply; 10+ messages in thread
From: Matthew Wilcox @ 2026-02-09 20:04 UTC (permalink / raw)
To: Andi Kleen; +Cc: linux-mm, linux-fsdevel, akpm
On Mon, Feb 09, 2026 at 11:32:23AM -0800, Andi Kleen wrote:
> + } else {
> + unsigned ps = vma_mmu_pagesize(vma);
> + /* Will need adjustments when more THP page sizes are added. */
> + SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
> + if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
> + ps != HPAGE_PMD_SIZE)
> + SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
> + }
I'm not a fan of adding support for just two page sizes when we already
know that we need to support many. Particularly not with such an
uninformative name as "MMUPageSize2".
Something like MMUOtherPageSizes: 64Kib,256KiB,2MiB would work for me.
But maybe other people have better ideas.
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] smaps: Report correct page sizes with THP
2026-02-09 20:04 ` Matthew Wilcox
@ 2026-02-09 20:10 ` Andi Kleen
0 siblings, 0 replies; 10+ messages in thread
From: Andi Kleen @ 2026-02-09 20:10 UTC (permalink / raw)
To: Matthew Wilcox; +Cc: linux-mm, linux-fsdevel, akpm
On Mon, Feb 09, 2026 at 08:04:38PM +0000, Matthew Wilcox wrote:
> On Mon, Feb 09, 2026 at 11:32:23AM -0800, Andi Kleen wrote:
> > + } else {
> > + unsigned ps = vma_mmu_pagesize(vma);
> > + /* Will need adjustments when more THP page sizes are added. */
> > + SEQ_PUT_DEC(" kB\nMMUPageSize: ", ps);
> > + if (mss.shmem_thp + mss.file_thp + mss.anonymous_thp > 0 &&
> > + ps != HPAGE_PMD_SIZE)
> > + SEQ_PUT_DEC(" kB\nMMUPageSize2: ", HPAGE_PMD_SIZE);
> > + }
>
> I'm not a fan of adding support for just two page sizes when we already
> know that we need to support many. Particularly not with such an
> uninformative name as "MMUPageSize2".
What is uninformative about it?
I intentionally used the number to make it extensible for the future,
you can add MMUPageSize3 and 4 and beyond, although the current code doesn't
implement it.
>
> Something like MMUOtherPageSizes: 64Kib,256KiB,2MiB would work for me.
> But maybe other people have better ideas.
I considered just adding the numbers to a single line (the existing one),
but the risk of breaking some existing parser seemed too high. No other entry
in smaps has multiple numbers, and it seems to be against standard /proc
conventions.
-Andi
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2026-02-21 0:03 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-02-09 20:17 [PATCH] smaps: Report correct page sizes with THP Andi Kleen
2026-02-12 12:42 ` David Hildenbrand (Arm)
2026-02-12 17:58 ` Andi Kleen
2026-02-12 18:05 ` David Hildenbrand (Arm)
2026-02-21 0:03 ` jane.chu
-- strict thread matches above, loose matches on Subject: below --
2026-02-11 2:59 kernel test robot
2026-02-09 21:31 kernel test robot
2026-02-09 19:32 Andi Kleen
2026-02-09 20:04 ` Matthew Wilcox
2026-02-09 20:10 ` Andi Kleen
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