On Mon, Aug 31, 2026 at 12:13:08PM +0200, Eli Billauer wrote: > On 30/08/2026 9:47, Mike Rapoport (Microsoft) wrote: > > fifo_init() allocates the buffers backing the software FIFO and > > endpoint_alloc() allocates the transfer buffers of a USB endpoint. > > > > These buffers can be allocated with kmalloc() as there's nothing special > > about them to go directly to the page allocator. > > Except that they are a bit large. > > fifo_init() may be requested to allocate up to 256 MB of buffer memory. This > memory resource is split into an array of buffers (fifo->mem[i]), each 64 > kiB (or less, if there's trouble obtaining segments of this size). > > Citing Documentation/core-api/memory-allocation.rst: > > "The maximal size of a chunk that can be allocated with `kmalloc` is > limited. The actual limit depends on the hardware and the kernel > configuration, but it is a good practice to use `kmalloc` for objects > smaller than page size."
For large sizes kmalloc falls back to page allocator anyway. And the doc is out of date unfortunately. > Regards, > Eli -- Sincerely yours, Mike.
