mbox series

[RFC,0/2] Add flag as THP allocation hint for memfd_restricted() syscall

Message ID cover.1676680548.git.ackerleytng@google.com
Headers
Series Add flag as THP allocation hint for memfd_restricted() syscall |

Message

Ackerley Tng Feb. 18, 2023, 12:43 a.m. UTC 
  Hello,

This patchset builds upon the memfd_restricted() system call that has
been discussed in the ‘KVM: mm: fd-based approach for supporting KVM’
patch series, at
https://lore.kernel.org/lkml/20221202061347.1070246-1-chao.p.peng@linux.intel.com/T/#m7e944d7892afdd1d62a03a287bd488c56e377b0c

The tree can be found at:
https://github.com/googleprodkernel/linux-cc/tree/restrictedmem-rmfd-hugepage

Following the RFC to provide mount for memfd_restricted() syscall at
https://lore.kernel.org/lkml/cover.1676507663.git.ackerleytng@google.com/T/#u,
this patchset adds the RMFD_HUGEPAGE flag to the memfd_restricted()
syscall, which will hint the kernel to use Transparent HugePages to
back restrictedmem pages.

This supplements the interface proposed earlier, which requires the
creation of a tmpfs mount to be passed to memfd_restricted(), with a
more direct per-file hint.

Dependencies:

+ Sean’s iteration of the ‘KVM: mm: fd-based approach for supporting
  KVM’ patch series at
  https://github.com/sean-jc/linux/tree/x86/upm_base_support
+ Proposed fix for restrictedmem_getattr() as mentioned on the mailing
  list at
  https://lore.kernel.org/lkml/diqzzga0fv96.fsf@ackerleytng-cloudtop-sg.c.googlers.com/
+ Hugh’s patch:
  https://lore.kernel.org/lkml/c140f56a-1aa3-f7ae-b7d1-93da7d5a3572@google.com/,
  which provides functionality in shmem that reads the VM_HUGEPAGE
  flag in key functions shmem_is_huge() and shmem_get_inode()

Future work/TODOs:
+ man page for the memfd_restricted() syscall
+ Support for per file NUMA binding hints

Ackerley Tng (2):
  mm: restrictedmem: Add flag as THP allocation hint for
    memfd_restricted() syscall
  selftests: restrictedmem: Add selftest for RMFD_HUGEPAGE

 include/uapi/linux/restrictedmem.h            |  1 +
 mm/restrictedmem.c                            | 27 ++++++++++++-------
 .../restrictedmem_hugepage_test.c             | 25 +++++++++++++++++
 3 files changed, 43 insertions(+), 10 deletions(-)

--
2.39.2.637.g21b0678d19-goog

Comments

Yuan Yao Feb. 20, 2023, 3:04 a.m. UTC | #1 
On Sat, Feb 18, 2023 at 12:43:00AM +0000, Ackerley Tng wrote:
> Hello,
>
> This patchset builds upon the memfd_restricted() system call that has
> been discussed in the ‘KVM: mm: fd-based approach for supporting KVM’
> patch series, at
> https://lore.kernel.org/lkml/20221202061347.1070246-1-chao.p.peng@linux.intel.com/T/#m7e944d7892afdd1d62a03a287bd488c56e377b0c
>
> The tree can be found at:
> https://github.com/googleprodkernel/linux-cc/tree/restrictedmem-rmfd-hugepage
>
> Following the RFC to provide mount for memfd_restricted() syscall at
> https://lore.kernel.org/lkml/cover.1676507663.git.ackerleytng@google.com/T/#u,
> this patchset adds the RMFD_HUGEPAGE flag to the memfd_restricted()
> syscall, which will hint the kernel to use Transparent HugePages to
> back restrictedmem pages.
>
> This supplements the interface proposed earlier, which requires the
> creation of a tmpfs mount to be passed to memfd_restricted(), with a
> more direct per-file hint.
>
> Dependencies:
>
> + Sean’s iteration of the ‘KVM: mm: fd-based approach for supporting
>   KVM’ patch series at
>   https://github.com/sean-jc/linux/tree/x86/upm_base_support
> + Proposed fix for restrictedmem_getattr() as mentioned on the mailing
>   list at
>   https://lore.kernel.org/lkml/diqzzga0fv96.fsf@ackerleytng-cloudtop-sg.c.googlers.com/
> + Hugh’s patch:
>   https://lore.kernel.org/lkml/c140f56a-1aa3-f7ae-b7d1-93da7d5a3572@google.com/,
>   which provides functionality in shmem that reads the VM_HUGEPAGE
>   flag in key functions shmem_is_huge() and shmem_get_inode()

Will Hugh's patch be merged into 6.3 ? I didn't find it in 6.2-rc8.
IMHO this patch won't work without Hugh's patch, or at least need
another way, e.g. HMEM_SB(inode->i_sb)->huge.

>
> Future work/TODOs:
> + man page for the memfd_restricted() syscall
> + Support for per file NUMA binding hints
>
> Ackerley Tng (2):
>   mm: restrictedmem: Add flag as THP allocation hint for
>     memfd_restricted() syscall
>   selftests: restrictedmem: Add selftest for RMFD_HUGEPAGE
>
>  include/uapi/linux/restrictedmem.h            |  1 +
>  mm/restrictedmem.c                            | 27 ++++++++++++-------
>  .../restrictedmem_hugepage_test.c             | 25 +++++++++++++++++
>  3 files changed, 43 insertions(+), 10 deletions(-)
>
> --
> 2.39.2.637.g21b0678d19-goog
>
Ackerley Tng Feb. 23, 2023, 1:31 a.m. UTC | #2 
Yuan Yao <yuan.yao@linux.intel.com> writes:

> On Sat, Feb 18, 2023 at 12:43:00AM +0000, Ackerley Tng wrote:
>> Hello,

>> This patchset builds upon the memfd_restricted() system call that has
>> been discussed in the ‘KVM: mm: fd-based approach for supporting KVM’
>> patch series, at
>> https://lore.kernel.org/lkml/20221202061347.1070246-1-chao.p.peng@linux.intel.com/T/#m7e944d7892afdd1d62a03a287bd488c56e377b0c

>> The tree can be found at:
>> https://github.com/googleprodkernel/linux-cc/tree/restrictedmem-rmfd-hugepage

>> Following the RFC to provide mount for memfd_restricted() syscall at
>> https://lore.kernel.org/lkml/cover.1676507663.git.ackerleytng@google.com/T/#u,
>> this patchset adds the RMFD_HUGEPAGE flag to the memfd_restricted()
>> syscall, which will hint the kernel to use Transparent HugePages to
>> back restrictedmem pages.

>> This supplements the interface proposed earlier, which requires the
>> creation of a tmpfs mount to be passed to memfd_restricted(), with a
>> more direct per-file hint.

>> Dependencies:

>> + Sean’s iteration of the ‘KVM: mm: fd-based approach for supporting
>>    KVM’ patch series at
>>    https://github.com/sean-jc/linux/tree/x86/upm_base_support
>> + Proposed fix for restrictedmem_getattr() as mentioned on the mailing
>>    list at
>>     
>> https://lore.kernel.org/lkml/diqzzga0fv96.fsf@ackerleytng-cloudtop-sg.c.googlers.com/
>> + Hugh’s patch:
>>     
>> https://lore.kernel.org/lkml/c140f56a-1aa3-f7ae-b7d1-93da7d5a3572@google.com/,
>>    which provides functionality in shmem that reads the VM_HUGEPAGE
>>    flag in key functions shmem_is_huge() and shmem_get_inode()

> Will Hugh's patch be merged into 6.3 ? I didn't find it in 6.2-rc8.
> IMHO this patch won't work without Hugh's patch, or at least need
> another way, e.g. HMEM_SB(inode->i_sb)->huge.


Hugh's patch is still pending discussion and may not be merged so
soon. These patches will not work without Hugh's patch.

I would like to understand what the community thinks of the proposed
interface (RMFD_HUGEPAGE flag, passed to the memfd_restricted()
syscall). If this interface is favorably received, we can definitely
find another way for shmem to support this interface.

If I understand correctly, SHMEM_SB(inode->i_sb)->huge checks the state
of hugepage-ness for the superblock. Since the proposed interface will
only affect a single file, we will need something closer to

     bool shmem_is_huge(struct vm_area_struct *vma, struct inode *inode,
                        pgoff_t index, bool shmem_huge_force)
     {
             ...

             if (SHMEM_I(inode)->flags & VM_HUGEPAGE)
                     return true;

             ...
     }

from Hugh's patch.