Re: [f2fs-dev] [PATCH v2] f2fs: another way to set large folio by remembering inode number

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 05/28, Matthew Wilcox wrote:
> On Tue, May 26, 2026 at 01:10:55AM +0000, Jaegeuk Kim wrote:
> > Background
> > ----------
> > The primary use case is accelerating AI model loading, which demands
> > exceptionally high sequential read speeds. In our benchmarks on embedded
> > systems:
> >  - Using high-order page allocations allows the system to saturate the
> >    Universal Flash Storage (UFS) bandwidth, reaching 4 GB/s even at
> >    medium-to-low CPU frequencies.
> >  - In contrast, standard small folios cap performance at 2 GB/s.
> > 
> > The performance doubling stems directly from reducing CPU cycle overhead during
> > memory allocation.
> 
> When you say "AI model loading", are you mmap()ing the file of weights,
> or are you calling read() to load the file into anonymous memory?
> 
> This matters because for the first operation, you need to allocate folios
> of PMD size in order to make best use of TLB entries.  For the second
> operation, it's more important to iterate through the file quickly,
> freeing folios behind you after you access them so they're available
> for the next batch.

We deal with multiple options tho, what I'm looking at is mostly a preloading
models by mmap(MAP_POPULATE) which takes the readahead path bumping up the order
by 2. Previously I also looked at fadvise(WILLNEED), but gave up due to the
broken interface. OTOH, we use RWF_DONTCACHE for read() case, but I don't
think it's ideal for the best loading performance.

> 
> 
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