smaps: Report correct page sizes with THP
Subsystems (5)
PATCH 1/1 smaps: Report correct page sizes with THP
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.
--- Documentation/filesystems/proc.rst | 2 +- fs/proc/task_mmu.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 2 deletions(-)
Documentation/filesystems/proc.rst +1 -1
@@ -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.
fs/proc/task_mmu.c +13 -1
@@ -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);
Signature · 1 line
2.52.0
Quoted 43 lines · 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 <[email protected]>--- Documentation/filesystems/proc.rst | 2 +- fs/proc/task_mmu.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 2 deletions(-)Documentation/filesystems/proc.rst +1
-1@@ -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.fs/proc/task_mmu.c +6
-1@@ -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 {
fs/proc/task_mmu.c static int show_smap(struct seq_file *m, void *v) · line 1395
Quoted 10 lines
fs/proc/task_mmu.c +7
-0+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.
Signature · 3 lines
Cheers, David
Quoted 2 lines
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.
Quoted 5 lines
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.
Quoted 2 lines
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
Quoted 5 lines · Andi Kleen
Quoted 2 lines
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.
Quoted 7 lines
Quoted 6 lines
Especially the mixed thing is just nasty.
Once we go into cont-pte territory (or automatic pte coalescing by hardware) it all gets confusing.
Quoted 6 lines
In this case it can be extended to more.
Quoted 2 lines
Sorry, NAK.
Okay then just remove the page size if it's fictional outside hugetlb anyways?
I'm sure that would break some tooling.
Signature · 3 lines
Cheers, David
Quoted 43 lines · 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 <[email protected]>--- Documentation/filesystems/proc.rst | 2 +- fs/proc/task_mmu.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 2 deletions(-)Documentation/filesystems/proc.rst +1
-1@@ -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.fs/proc/task_mmu.c +6
-1@@ -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 {
fs/proc/task_mmu.c static int show_smap(struct seq_file *m, void *v) · line 1395
Quoted 10 lines
fs/proc/task_mmu.c +7
-0+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 <--thanks,
-jane