On 05/28, Matthew Wilcox wrote:

On Tue, May 26, 2026 at 01:10:55AM +0000, Jaegeuk Kim wrote:

quoted

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.

_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel