arch/arm64/include/asm/pgtable.h | 21 ++---- arch/arm64/mm/mteswap.c | 42 ++++++++++++ include/asm-generic/tlb.h | 10 +++ include/linux/huge_mm.h | 12 ---- include/linux/pgtable.h | 62 ++++++++++++++++- include/linux/swap.h | 6 ++ mm/madvise.c | 48 ++++++++++++++ mm/memory.c | 110 ++++++++++++++++++++++++++----- mm/page_io.c | 2 +- mm/rmap.c | 5 +- mm/swap_slots.c | 2 +- mm/swapfile.c | 29 ++++++++ 12 files changed, 301 insertions(+), 48 deletions(-)
On an embedded system like Android, more than half of anon memory is actually in swap devices such as zRAM. For example, while an app is switched to back- ground, its most memory might be swapped-out. Now we have mTHP features, unfortunately, if we don't support large folios swap-in, once those large folios are swapped-out, we immediately lose the performance gain we can get through large folios and hardware optimization such as CONT-PTE. In theory, we don't need to rely on Ryan's swap out patchset[1]. That is to say, before swap-out, if some memory were normal pages, but when swapping in, we can also swap-in them as large folios. But this might require I/O happen at some random places in swap devices. So we limit the large folios swap-in to those areas which were large folios before swapping-out, aka, swaps are also contiguous in hardware. On the other hand, in OPPO's product, we've deployed anon large folios on millions of phones[2]. we enhanced zsmalloc and zRAM to compress and decompress large folios as a whole, which help improve compression ratio and decrease CPU consumption significantly. In zsmalloc and zRAM we can save large objects whose original size are 64KiB for example. So it is also a better choice for us to only swap-in large folios for those compressed large objects as a large folio can be decompressed all together. Note I am moving my previous "arm64: mm: swap: support THP_SWAP on hardware with MTE" to this series as it might help review. [1] [PATCH v3 0/4] Swap-out small-sized THP without splitting https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/ [2] OnePlusOSS / android_kernel_oneplus_sm8550 https://github.com/OnePlusOSS/android_kernel_oneplus_sm8550/tree/oneplus/sm8550_u_14.0.0_oneplus11 Barry Song (2): arm64: mm: swap: support THP_SWAP on hardware with MTE mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap() Chuanhua Han (4): mm: swap: introduce swap_nr_free() for batched swap_free() mm: swap: make should_try_to_free_swap() support large-folio mm: support large folios swapin as a whole mm: madvise: don't split mTHP for MADV_PAGEOUT arch/arm64/include/asm/pgtable.h | 21 ++---- arch/arm64/mm/mteswap.c | 42 ++++++++++++ include/asm-generic/tlb.h | 10 +++ include/linux/huge_mm.h | 12 ---- include/linux/pgtable.h | 62 ++++++++++++++++- include/linux/swap.h | 6 ++ mm/madvise.c | 48 ++++++++++++++ mm/memory.c | 110 ++++++++++++++++++++++++++----- mm/page_io.c | 2 +- mm/rmap.c | 5 +- mm/swap_slots.c | 2 +- mm/swapfile.c | 29 ++++++++ 12 files changed, 301 insertions(+), 48 deletions(-) -- 2.34.1
On 18/01/2024 11:10, Barry Song wrote: > On an embedded system like Android, more than half of anon memory is actually > in swap devices such as zRAM. For example, while an app is switched to back- > ground, its most memory might be swapped-out. > > Now we have mTHP features, unfortunately, if we don't support large folios > swap-in, once those large folios are swapped-out, we immediately lose the > performance gain we can get through large folios and hardware optimization > such as CONT-PTE. > > In theory, we don't need to rely on Ryan's swap out patchset[1]. That is to say, > before swap-out, if some memory were normal pages, but when swapping in, we > can also swap-in them as large folios. I think this could also violate MADV_NOHUGEPAGE; if the application has requested that we do not create a THP, then we had better not; it could cause a correctness issue in some circumstances. You would need to pay attention to this vma flag if taking this approach. > But this might require I/O happen at > some random places in swap devices. So we limit the large folios swap-in to > those areas which were large folios before swapping-out, aka, swaps are also > contiguous in hardware. In fact, even this may not be sufficient; it's possible that a contiguous set of base pages (small folios) were allocated to a virtual mapping and all swapped out together - they would likely end up contiguous in the swap file, but should not be swapped back in as a single folio because of this (same reasoning applies to cluster of smaller THPs that you mistake for a larger THP, etc). So you will need to check what THP sizes are enabled and check the VMA suitability regardless; Perhaps you are already doing this - I haven't looked at the code yet. I'll aim to review the code in the next couple of weeks. Thanks, Ryan > On the other hand, in OPPO's product, we've deployed > anon large folios on millions of phones[2]. we enhanced zsmalloc and zRAM to > compress and decompress large folios as a whole, which help improve compression > ratio and decrease CPU consumption significantly. In zsmalloc and zRAM we can > save large objects whose original size are 64KiB for example. So it is also a > better choice for us to only swap-in large folios for those compressed large > objects as a large folio can be decompressed all together. > > Note I am moving my previous "arm64: mm: swap: support THP_SWAP on hardware > with MTE" to this series as it might help review. > > [1] [PATCH v3 0/4] Swap-out small-sized THP without splitting > https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/ > [2] OnePlusOSS / android_kernel_oneplus_sm8550 > https://github.com/OnePlusOSS/android_kernel_oneplus_sm8550/tree/oneplus/sm8550_u_14.0.0_oneplus11 > > Barry Song (2): > arm64: mm: swap: support THP_SWAP on hardware with MTE > mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap() > > Chuanhua Han (4): > mm: swap: introduce swap_nr_free() for batched swap_free() > mm: swap: make should_try_to_free_swap() support large-folio > mm: support large folios swapin as a whole > mm: madvise: don't split mTHP for MADV_PAGEOUT > > arch/arm64/include/asm/pgtable.h | 21 ++---- > arch/arm64/mm/mteswap.c | 42 ++++++++++++ > include/asm-generic/tlb.h | 10 +++ > include/linux/huge_mm.h | 12 ---- > include/linux/pgtable.h | 62 ++++++++++++++++- > include/linux/swap.h | 6 ++ > mm/madvise.c | 48 ++++++++++++++ > mm/memory.c | 110 ++++++++++++++++++++++++++----- > mm/page_io.c | 2 +- > mm/rmap.c | 5 +- > mm/swap_slots.c | 2 +- > mm/swapfile.c | 29 ++++++++ > 12 files changed, 301 insertions(+), 48 deletions(-) >
On Thu, Jan 18, 2024 at 11:25 PM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> On 18/01/2024 11:10, Barry Song wrote:
> > On an embedded system like Android, more than half of anon memory is actually
> > in swap devices such as zRAM. For example, while an app is switched to back-
> > ground, its most memory might be swapped-out.
> >
> > Now we have mTHP features, unfortunately, if we don't support large folios
> > swap-in, once those large folios are swapped-out, we immediately lose the
> > performance gain we can get through large folios and hardware optimization
> > such as CONT-PTE.
> >
> > In theory, we don't need to rely on Ryan's swap out patchset[1]. That is to say,
> > before swap-out, if some memory were normal pages, but when swapping in, we
> > can also swap-in them as large folios.
>
> I think this could also violate MADV_NOHUGEPAGE; if the application has
> requested that we do not create a THP, then we had better not; it could cause a
> correctness issue in some circumstances. You would need to pay attention to this
> vma flag if taking this approach.
>
> > But this might require I/O happen at
> > some random places in swap devices. So we limit the large folios swap-in to
> > those areas which were large folios before swapping-out, aka, swaps are also
> > contiguous in hardware.
>
> In fact, even this may not be sufficient; it's possible that a contiguous set of
> base pages (small folios) were allocated to a virtual mapping and all swapped
> out together - they would likely end up contiguous in the swap file, but should
> not be swapped back in as a single folio because of this (same reasoning applies
> to cluster of smaller THPs that you mistake for a larger THP, etc).
>
> So you will need to check what THP sizes are enabled and check the VMA
> suitability regardless; Perhaps you are already doing this - I haven't looked at
> the code yet.
we are actually re-using your alloc_anon_folio() by adding a parameter
to make it
support both do_anon_page and do_swap_page,
-static struct folio *alloc_anon_folio(struct vm_fault *vmf)
+static struct folio *alloc_anon_folio(struct vm_fault *vmf,
+ bool (*pte_range_check)(pte_t *, int))
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct vm_area_struct *vma = vmf->vma;
@@ -4190,7 +4270,7 @@ static struct folio *alloc_anon_folio(struct
vm_fault *vmf)
order = highest_order(orders);
while (orders) {
addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order);
- if (pte_range_none(pte + pte_index(addr), 1 << order))
+ if (pte_range_check(pte + pte_index(addr), 1 << order))
break;
order = next_order(&orders, order);
}
@@ -4269,7 +4349,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
if (unlikely(anon_vma_prepare(vma)))
goto oom;
/* Returns NULL on OOM or ERR_PTR(-EAGAIN) if we must retry the fault */
- folio = alloc_anon_folio(vmf);
+ folio = alloc_anon_folio(vmf, pte_range_none);
if (IS_ERR(folio))
return 0;
if (!folio)
--
I assume this has checked everything?
>
> I'll aim to review the code in the next couple of weeks.
nice, thanks!
>
> Thanks,
> Ryan
>
> > On the other hand, in OPPO's product, we've deployed
> > anon large folios on millions of phones[2]. we enhanced zsmalloc and zRAM to
> > compress and decompress large folios as a whole, which help improve compression
> > ratio and decrease CPU consumption significantly. In zsmalloc and zRAM we can
> > save large objects whose original size are 64KiB for example. So it is also a
> > better choice for us to only swap-in large folios for those compressed large
> > objects as a large folio can be decompressed all together.
> >
> > Note I am moving my previous "arm64: mm: swap: support THP_SWAP on hardware
> > with MTE" to this series as it might help review.
> >
> > [1] [PATCH v3 0/4] Swap-out small-sized THP without splitting
> > https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/
> > [2] OnePlusOSS / android_kernel_oneplus_sm8550
> > https://github.com/OnePlusOSS/android_kernel_oneplus_sm8550/tree/oneplus/sm8550_u_14.0.0_oneplus11
> >
> > Barry Song (2):
> > arm64: mm: swap: support THP_SWAP on hardware with MTE
> > mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap()
> >
> > Chuanhua Han (4):
> > mm: swap: introduce swap_nr_free() for batched swap_free()
> > mm: swap: make should_try_to_free_swap() support large-folio
> > mm: support large folios swapin as a whole
> > mm: madvise: don't split mTHP for MADV_PAGEOUT
> >
> > arch/arm64/include/asm/pgtable.h | 21 ++----
> > arch/arm64/mm/mteswap.c | 42 ++++++++++++
> > include/asm-generic/tlb.h | 10 +++
> > include/linux/huge_mm.h | 12 ----
> > include/linux/pgtable.h | 62 ++++++++++++++++-
> > include/linux/swap.h | 6 ++
> > mm/madvise.c | 48 ++++++++++++++
> > mm/memory.c | 110 ++++++++++++++++++++++++++-----
> > mm/page_io.c | 2 +-
> > mm/rmap.c | 5 +-
> > mm/swap_slots.c | 2 +-
> > mm/swapfile.c | 29 ++++++++
> > 12 files changed, 301 insertions(+), 48 deletions(-)
> >
>
Thanks
Barry
On 18/01/2024 23:54, Barry Song wrote:
> On Thu, Jan 18, 2024 at 11:25 PM Ryan Roberts <ryan.roberts@arm.com> wrote:
>>
>> On 18/01/2024 11:10, Barry Song wrote:
>>> On an embedded system like Android, more than half of anon memory is actually
>>> in swap devices such as zRAM. For example, while an app is switched to back-
>>> ground, its most memory might be swapped-out.
>>>
>>> Now we have mTHP features, unfortunately, if we don't support large folios
>>> swap-in, once those large folios are swapped-out, we immediately lose the
>>> performance gain we can get through large folios and hardware optimization
>>> such as CONT-PTE.
>>>
>>> In theory, we don't need to rely on Ryan's swap out patchset[1]. That is to say,
>>> before swap-out, if some memory were normal pages, but when swapping in, we
>>> can also swap-in them as large folios.
>>
>> I think this could also violate MADV_NOHUGEPAGE; if the application has
>> requested that we do not create a THP, then we had better not; it could cause a
>> correctness issue in some circumstances. You would need to pay attention to this
>> vma flag if taking this approach.
>>
>>> But this might require I/O happen at
>>> some random places in swap devices. So we limit the large folios swap-in to
>>> those areas which were large folios before swapping-out, aka, swaps are also
>>> contiguous in hardware.
>>
>> In fact, even this may not be sufficient; it's possible that a contiguous set of
>> base pages (small folios) were allocated to a virtual mapping and all swapped
>> out together - they would likely end up contiguous in the swap file, but should
>> not be swapped back in as a single folio because of this (same reasoning applies
>> to cluster of smaller THPs that you mistake for a larger THP, etc).
>>
>> So you will need to check what THP sizes are enabled and check the VMA
>> suitability regardless; Perhaps you are already doing this - I haven't looked at
>> the code yet.
>
> we are actually re-using your alloc_anon_folio() by adding a parameter
> to make it
> support both do_anon_page and do_swap_page,
>
> -static struct folio *alloc_anon_folio(struct vm_fault *vmf)
> +static struct folio *alloc_anon_folio(struct vm_fault *vmf,
> + bool (*pte_range_check)(pte_t *, int))
> {
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> struct vm_area_struct *vma = vmf->vma;
> @@ -4190,7 +4270,7 @@ static struct folio *alloc_anon_folio(struct
> vm_fault *vmf)
> order = highest_order(orders);
> while (orders) {
> addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order);
> - if (pte_range_none(pte + pte_index(addr), 1 << order))
> + if (pte_range_check(pte + pte_index(addr), 1 << order))
> break;
> order = next_order(&orders, order);
> }
> @@ -4269,7 +4349,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> if (unlikely(anon_vma_prepare(vma)))
> goto oom;
> /* Returns NULL on OOM or ERR_PTR(-EAGAIN) if we must retry the fault */
> - folio = alloc_anon_folio(vmf);
> + folio = alloc_anon_folio(vmf, pte_range_none);
> if (IS_ERR(folio))
> return 0;
> if (!folio)
> --
>
> I assume this has checked everything?
Ahh yes, very good. In that case you can disregard what I said; its already covered.
I notice that this series appears as a reply to my series. I'm not sure what the
normal convention is, but I expect more people would see it if you posted it as
its own thread?
>
>>
>> I'll aim to review the code in the next couple of weeks.
>
> nice, thanks!
>
>>
>> Thanks,
>> Ryan
>>
>>> On the other hand, in OPPO's product, we've deployed
>>> anon large folios on millions of phones[2]. we enhanced zsmalloc and zRAM to
>>> compress and decompress large folios as a whole, which help improve compression
>>> ratio and decrease CPU consumption significantly. In zsmalloc and zRAM we can
>>> save large objects whose original size are 64KiB for example. So it is also a
>>> better choice for us to only swap-in large folios for those compressed large
>>> objects as a large folio can be decompressed all together.
>>>
>>> Note I am moving my previous "arm64: mm: swap: support THP_SWAP on hardware
>>> with MTE" to this series as it might help review.
>>>
>>> [1] [PATCH v3 0/4] Swap-out small-sized THP without splitting
>>> https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/
>>> [2] OnePlusOSS / android_kernel_oneplus_sm8550
>>> https://github.com/OnePlusOSS/android_kernel_oneplus_sm8550/tree/oneplus/sm8550_u_14.0.0_oneplus11
>>>
>>> Barry Song (2):
>>> arm64: mm: swap: support THP_SWAP on hardware with MTE
>>> mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap()
>>>
>>> Chuanhua Han (4):
>>> mm: swap: introduce swap_nr_free() for batched swap_free()
>>> mm: swap: make should_try_to_free_swap() support large-folio
>>> mm: support large folios swapin as a whole
>>> mm: madvise: don't split mTHP for MADV_PAGEOUT
>>>
>>> arch/arm64/include/asm/pgtable.h | 21 ++----
>>> arch/arm64/mm/mteswap.c | 42 ++++++++++++
>>> include/asm-generic/tlb.h | 10 +++
>>> include/linux/huge_mm.h | 12 ----
>>> include/linux/pgtable.h | 62 ++++++++++++++++-
>>> include/linux/swap.h | 6 ++
>>> mm/madvise.c | 48 ++++++++++++++
>>> mm/memory.c | 110 ++++++++++++++++++++++++++-----
>>> mm/page_io.c | 2 +-
>>> mm/rmap.c | 5 +-
>>> mm/swap_slots.c | 2 +-
>>> mm/swapfile.c | 29 ++++++++
>>> 12 files changed, 301 insertions(+), 48 deletions(-)
>>>
>>
>
> Thanks
> Barry
On Fri, Jan 19, 2024 at 9:25 PM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> On 18/01/2024 23:54, Barry Song wrote:
> > On Thu, Jan 18, 2024 at 11:25 PM Ryan Roberts <ryan.roberts@arm.com> wrote:
> >>
> >> On 18/01/2024 11:10, Barry Song wrote:
> >>> On an embedded system like Android, more than half of anon memory is actually
> >>> in swap devices such as zRAM. For example, while an app is switched to back-
> >>> ground, its most memory might be swapped-out.
> >>>
> >>> Now we have mTHP features, unfortunately, if we don't support large folios
> >>> swap-in, once those large folios are swapped-out, we immediately lose the
> >>> performance gain we can get through large folios and hardware optimization
> >>> such as CONT-PTE.
> >>>
> >>> In theory, we don't need to rely on Ryan's swap out patchset[1]. That is to say,
> >>> before swap-out, if some memory were normal pages, but when swapping in, we
> >>> can also swap-in them as large folios.
> >>
> >> I think this could also violate MADV_NOHUGEPAGE; if the application has
> >> requested that we do not create a THP, then we had better not; it could cause a
> >> correctness issue in some circumstances. You would need to pay attention to this
> >> vma flag if taking this approach.
> >>
> >>> But this might require I/O happen at
> >>> some random places in swap devices. So we limit the large folios swap-in to
> >>> those areas which were large folios before swapping-out, aka, swaps are also
> >>> contiguous in hardware.
> >>
> >> In fact, even this may not be sufficient; it's possible that a contiguous set of
> >> base pages (small folios) were allocated to a virtual mapping and all swapped
> >> out together - they would likely end up contiguous in the swap file, but should
> >> not be swapped back in as a single folio because of this (same reasoning applies
> >> to cluster of smaller THPs that you mistake for a larger THP, etc).
> >>
> >> So you will need to check what THP sizes are enabled and check the VMA
> >> suitability regardless; Perhaps you are already doing this - I haven't looked at
> >> the code yet.
> >
> > we are actually re-using your alloc_anon_folio() by adding a parameter
> > to make it
> > support both do_anon_page and do_swap_page,
> >
> > -static struct folio *alloc_anon_folio(struct vm_fault *vmf)
> > +static struct folio *alloc_anon_folio(struct vm_fault *vmf,
> > + bool (*pte_range_check)(pte_t *, int))
> > {
> > #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > struct vm_area_struct *vma = vmf->vma;
> > @@ -4190,7 +4270,7 @@ static struct folio *alloc_anon_folio(struct
> > vm_fault *vmf)
> > order = highest_order(orders);
> > while (orders) {
> > addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order);
> > - if (pte_range_none(pte + pte_index(addr), 1 << order))
> > + if (pte_range_check(pte + pte_index(addr), 1 << order))
> > break;
> > order = next_order(&orders, order);
> > }
> > @@ -4269,7 +4349,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> > if (unlikely(anon_vma_prepare(vma)))
> > goto oom;
> > /* Returns NULL on OOM or ERR_PTR(-EAGAIN) if we must retry the fault */
> > - folio = alloc_anon_folio(vmf);
> > + folio = alloc_anon_folio(vmf, pte_range_none);
> > if (IS_ERR(folio))
> > return 0;
> > if (!folio)
> > --
> >
> > I assume this has checked everything?
>
> Ahh yes, very good. In that case you can disregard what I said; its already covered.
>
> I notice that this series appears as a reply to my series. I'm not sure what the
> normal convention is, but I expect more people would see it if you posted it as
> its own thread?
yes. i was replying your series because we were using your series to
swapout large folios
without splitting. in v2, i will send it as a new thread.
>
>
> >
> >>
> >> I'll aim to review the code in the next couple of weeks.
> >
> > nice, thanks!
> >
> >>
> >> Thanks,
> >> Ryan
> >>
> >>> On the other hand, in OPPO's product, we've deployed
> >>> anon large folios on millions of phones[2]. we enhanced zsmalloc and zRAM to
> >>> compress and decompress large folios as a whole, which help improve compression
> >>> ratio and decrease CPU consumption significantly. In zsmalloc and zRAM we can
> >>> save large objects whose original size are 64KiB for example. So it is also a
> >>> better choice for us to only swap-in large folios for those compressed large
> >>> objects as a large folio can be decompressed all together.
> >>>
> >>> Note I am moving my previous "arm64: mm: swap: support THP_SWAP on hardware
> >>> with MTE" to this series as it might help review.
> >>>
> >>> [1] [PATCH v3 0/4] Swap-out small-sized THP without splitting
> >>> https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/
> >>> [2] OnePlusOSS / android_kernel_oneplus_sm8550
> >>> https://github.com/OnePlusOSS/android_kernel_oneplus_sm8550/tree/oneplus/sm8550_u_14.0.0_oneplus11
> >>>
> >>> Barry Song (2):
> >>> arm64: mm: swap: support THP_SWAP on hardware with MTE
> >>> mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap()
> >>>
> >>> Chuanhua Han (4):
> >>> mm: swap: introduce swap_nr_free() for batched swap_free()
> >>> mm: swap: make should_try_to_free_swap() support large-folio
> >>> mm: support large folios swapin as a whole
> >>> mm: madvise: don't split mTHP for MADV_PAGEOUT
> >>>
> >>> arch/arm64/include/asm/pgtable.h | 21 ++----
> >>> arch/arm64/mm/mteswap.c | 42 ++++++++++++
> >>> include/asm-generic/tlb.h | 10 +++
> >>> include/linux/huge_mm.h | 12 ----
> >>> include/linux/pgtable.h | 62 ++++++++++++++++-
> >>> include/linux/swap.h | 6 ++
> >>> mm/madvise.c | 48 ++++++++++++++
> >>> mm/memory.c | 110 ++++++++++++++++++++++++++-----
> >>> mm/page_io.c | 2 +-
> >>> mm/rmap.c | 5 +-
> >>> mm/swap_slots.c | 2 +-
> >>> mm/swapfile.c | 29 ++++++++
> >>> 12 files changed, 301 insertions(+), 48 deletions(-)
> >>>
> >>
> >
Thanks
Barry
>
Barry Song <21cnbao@gmail.com> writes: > On an embedded system like Android, more than half of anon memory is actually > in swap devices such as zRAM. For example, while an app is switched to back- > ground, its most memory might be swapped-out. > > Now we have mTHP features, unfortunately, if we don't support large folios > swap-in, once those large folios are swapped-out, we immediately lose the > performance gain we can get through large folios and hardware optimization > such as CONT-PTE. > > In theory, we don't need to rely on Ryan's swap out patchset[1]. That is to say, > before swap-out, if some memory were normal pages, but when swapping in, we > can also swap-in them as large folios. But this might require I/O happen at > some random places in swap devices. So we limit the large folios swap-in to > those areas which were large folios before swapping-out, aka, swaps are also > contiguous in hardware. On the other hand, in OPPO's product, we've deployed > anon large folios on millions of phones[2]. we enhanced zsmalloc and zRAM to > compress and decompress large folios as a whole, which help improve compression > ratio and decrease CPU consumption significantly. In zsmalloc and zRAM we can > save large objects whose original size are 64KiB for example. So it is also a > better choice for us to only swap-in large folios for those compressed large > objects as a large folio can be decompressed all together. Another possibility is to combine large folios swap-in with VMA based swap-in readahead. If we will swap-in readahead several pages based on VMA, we can swap-in a large folio instead. I think that it is similar as allocating large file folios for file readahead (TBH, I haven't check file large folios allocation code). -- Best Regards, Huang, Ying > Note I am moving my previous "arm64: mm: swap: support THP_SWAP on hardware > with MTE" to this series as it might help review. > > [1] [PATCH v3 0/4] Swap-out small-sized THP without splitting > https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/ > [2] OnePlusOSS / android_kernel_oneplus_sm8550 > https://github.com/OnePlusOSS/android_kernel_oneplus_sm8550/tree/oneplus/sm8550_u_14.0.0_oneplus11 > > Barry Song (2): > arm64: mm: swap: support THP_SWAP on hardware with MTE > mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap() > > Chuanhua Han (4): > mm: swap: introduce swap_nr_free() for batched swap_free() > mm: swap: make should_try_to_free_swap() support large-folio > mm: support large folios swapin as a whole > mm: madvise: don't split mTHP for MADV_PAGEOUT > > arch/arm64/include/asm/pgtable.h | 21 ++---- > arch/arm64/mm/mteswap.c | 42 ++++++++++++ > include/asm-generic/tlb.h | 10 +++ > include/linux/huge_mm.h | 12 ---- > include/linux/pgtable.h | 62 ++++++++++++++++- > include/linux/swap.h | 6 ++ > mm/madvise.c | 48 ++++++++++++++ > mm/memory.c | 110 ++++++++++++++++++++++++++----- > mm/page_io.c | 2 +- > mm/rmap.c | 5 +- > mm/swap_slots.c | 2 +- > mm/swapfile.c | 29 ++++++++ > 12 files changed, 301 insertions(+), 48 deletions(-)
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