[f2fs-dev] Plans for F2FS Supporting Large Folios

[f2fs-dev] Plans for F2FS Supporting Large Folios

[Ryan Roberts]

Hi Jaegeuk Kim, Chao Yu,

I heard (via Matthew Wilcox) that you may be in the process of forming plans to
add large folio support to f2fs? If so, I wonder if you could let me know how
those plans are progressing? I saw your v6.12-rc1 pull request did a lot of
conversion from struct page to struct folio (of the small variety for now) but
wondered if this is intended as pre-work for enabling large folios?

I've been doing a lot of work on the anonymous memory side to support large
folios ("mTHP") and hook that up to arm64's contpte pgtable support. This
improves performance nicely.

Additionally I have experimented (on XFS) with ensuring that text mappings are
contpte mapped where possible and this reduces pressure in the iTLB to improve
performance further. But it all relies on the file system supporting large
folios. I'd very much like to realize these performance gains on Android, but
that requires the file systems that Android uses to support large folios.

It would be great to understand your plans, if any, and figure out if/where Arm
may be able to help accelerate activities in this area. I'm not (yet!) an fs
expert, but I see that f2fs is already using iomap, so perhaps now that you are
supporting small folios, switching up to large folios is not too big of a step?

Thanks,
Ryan


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Re: [f2fs-dev] Plans for F2FS Supporting Large Folios

[Jaegeuk Kim via Linux-f2fs-devel]

Hi Ryan,

On 10/02, Ryan Roberts wrote:
> Hi Jaegeuk Kim, Chao Yu,
> 
> I heard (via Matthew Wilcox) that you may be in the process of forming plans to
> add large folio support to f2fs? If so, I wonder if you could let me know how
> those plans are progressing? I saw your v6.12-rc1 pull request did a lot of
> conversion from struct page to struct folio (of the small variety for now) but
> wondered if this is intended as pre-work for enabling large folios?
> 
> I've been doing a lot of work on the anonymous memory side to support large
> folios ("mTHP") and hook that up to arm64's contpte pgtable support. This
> improves performance nicely.
> 
> Additionally I have experimented (on XFS) with ensuring that text mappings are
> contpte mapped where possible and this reduces pressure in the iTLB to improve
> performance further. But it all relies on the file system supporting large
> folios. I'd very much like to realize these performance gains on Android, but
> that requires the file systems that Android uses to support large folios.
> 
> It would be great to understand your plans, if any, and figure out if/where Arm
> may be able to help accelerate activities in this area. I'm not (yet!) an fs
> expert, but I see that f2fs is already using iomap, so perhaps now that you are
> supporting small folios, switching up to large folios is not too big of a step?

Thanks for sharing the background. By any chance, have you talked larg folio
with Android kernel team? If indeed there's a fair benefit from Android side,
I'd like to circle back supporting it in f2fs seriously.

> 
> Thanks,
> Ryan


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Re: [f2fs-dev] Plans for F2FS Supporting Large Folios

[Ryan Roberts]

On 07/10/2024 17:38, Jaegeuk Kim wrote:
> Hi Ryan,
> 
> On 10/02, Ryan Roberts wrote:
>> Hi Jaegeuk Kim, Chao Yu,
>>
>> I heard (via Matthew Wilcox) that you may be in the process of forming plans to
>> add large folio support to f2fs? If so, I wonder if you could let me know how
>> those plans are progressing? I saw your v6.12-rc1 pull request did a lot of
>> conversion from struct page to struct folio (of the small variety for now) but
>> wondered if this is intended as pre-work for enabling large folios?
>>
>> I've been doing a lot of work on the anonymous memory side to support large
>> folios ("mTHP") and hook that up to arm64's contpte pgtable support. This
>> improves performance nicely.
>>
>> Additionally I have experimented (on XFS) with ensuring that text mappings are
>> contpte mapped where possible and this reduces pressure in the iTLB to improve
>> performance further. But it all relies on the file system supporting large
>> folios. I'd very much like to realize these performance gains on Android, but
>> that requires the file systems that Android uses to support large folios.
>>
>> It would be great to understand your plans, if any, and figure out if/where Arm
>> may be able to help accelerate activities in this area. I'm not (yet!) an fs
>> expert, but I see that f2fs is already using iomap, so perhaps now that you are
>> supporting small folios, switching up to large folios is not too big of a step?
> 
> Thanks for sharing the background. By any chance, have you talked larg folio
> with Android kernel team? 

Android kernel team are actively working (along with partners) to enable mTHP -
that's large folios for anonymous memory. They haven't yet got to looking
specifically at large-folios for file-backed memory. But I've had some informal
conversations with a couple of Android kernel team folks which have been
positive about the prospect.

If indeed there's a fair benefit from Android side,
> I'd like to circle back supporting it in f2fs seriously.

My own experiments have demonstrated performance uplift in Chromium web browsing
when using contpte-mapped code [1] (about 1.5% improvement on its own). We also
have plans to selectively use 2M THP (that's PMD-sized for 4K pages, or
contpte-sized for 16K pages) for some hot code, which previous experiments have
shown to be beneficial (I see about 2.5% for the same speedometer benchmark).
This all relies upon the filesystem supporting large folios though.

I'd really like to get large-folio support into f2fs to enable gathering more
performance data in a real Android environment. How best can be work together to
add this feature to f2fs?

[1] https://lore.kernel.org/linux-mm/20240717071257.4141363-3-ryan.roberts@arm.com/

Thanks,
Ryan

> 
>>
>> Thanks,
>> Ryan



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Re: [f2fs-dev] Plans for F2FS Supporting Large Folios

[Ryan Roberts]

Hi Jaegeuk,

Just a polite bump on the below...

On 09/10/2024 12:23, Ryan Roberts wrote:
> On 07/10/2024 17:38, Jaegeuk Kim wrote:
>> Hi Ryan,
>>
>> On 10/02, Ryan Roberts wrote:
>>> Hi Jaegeuk Kim, Chao Yu,
>>>
>>> I heard (via Matthew Wilcox) that you may be in the process of forming plans to
>>> add large folio support to f2fs? If so, I wonder if you could let me know how
>>> those plans are progressing? I saw your v6.12-rc1 pull request did a lot of
>>> conversion from struct page to struct folio (of the small variety for now) but
>>> wondered if this is intended as pre-work for enabling large folios?
>>>
>>> I've been doing a lot of work on the anonymous memory side to support large
>>> folios ("mTHP") and hook that up to arm64's contpte pgtable support. This
>>> improves performance nicely.
>>>
>>> Additionally I have experimented (on XFS) with ensuring that text mappings are
>>> contpte mapped where possible and this reduces pressure in the iTLB to improve
>>> performance further. But it all relies on the file system supporting large
>>> folios. I'd very much like to realize these performance gains on Android, but
>>> that requires the file systems that Android uses to support large folios.
>>>
>>> It would be great to understand your plans, if any, and figure out if/where Arm
>>> may be able to help accelerate activities in this area. I'm not (yet!) an fs
>>> expert, but I see that f2fs is already using iomap, so perhaps now that you are
>>> supporting small folios, switching up to large folios is not too big of a step?
>>
>> Thanks for sharing the background. By any chance, have you talked larg folio
>> with Android kernel team? 
> 
> Android kernel team are actively working (along with partners) to enable mTHP -
> that's large folios for anonymous memory. They haven't yet got to looking
> specifically at large-folios for file-backed memory. But I've had some informal
> conversations with a couple of Android kernel team folks which have been
> positive about the prospect.
> 
> If indeed there's a fair benefit from Android side,
>> I'd like to circle back supporting it in f2fs seriously.
> 
> My own experiments have demonstrated performance uplift in Chromium web browsing
> when using contpte-mapped code [1] (about 1.5% improvement on its own). We also
> have plans to selectively use 2M THP (that's PMD-sized for 4K pages, or
> contpte-sized for 16K pages) for some hot code, which previous experiments have
> shown to be beneficial (I see about 2.5% for the same speedometer benchmark).
> This all relies upon the filesystem supporting large folios though.
> 
> I'd really like to get large-folio support into f2fs to enable gathering more
> performance data in a real Android environment. How best can be work together to
> add this feature to f2fs?

Do you have any thoughts on this? Do you have plans to enable large folios? And
if not, then do you have any issue in principle with accepting a submission that
enables it?

Thanks,
Ryan

> 
> [1] https://lore.kernel.org/linux-mm/20240717071257.4141363-3-ryan.roberts@arm.com/
> 
> Thanks,
> Ryan
> 
>>
>>>
>>> Thanks,
>>> Ryan
> 



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