Le 27/02/2024 à 16:40, Arnd Bergmann a écrit : > On Mon, Feb 26, 2024, at 17:55, Samuel Holland wrote: >> On 2024-02-26 10:14 AM, Arnd Bergmann wrote: >>> >>> +config HAVE_PAGE_SIZE_4KB >>> + bool >>> + >>> +config HAVE_PAGE_SIZE_8KB >>> + bool >>> + >>> +config HAVE_PAGE_SIZE_16KB >>> + bool >>> + >>> +config HAVE_PAGE_SIZE_32KB >>> + bool >>> + >>> +config HAVE_PAGE_SIZE_64KB >>> + bool >>> + >>> +config HAVE_PAGE_SIZE_256KB >>> + bool >>> + >>> +choice >>> + prompt "MMU page size" >> >> Should this have some generic help text (at least a warning about >> compatibility)? > > Good point. I've added some of this now, based on the mips > text with some generalizations for other architectures: > > config PAGE_SIZE_4KB > bool "4KiB pages" > depends on HAVE_PAGE_SIZE_4KB > help > This option select the standard 4KiB Linux page size and the only > available option on many architectures. Using 4KiB page size will > minimize memory consumption and is therefore recommended for low > memory systems. > Some software that is written for x86 systems makes incorrect > assumptions about the page size and only runs on 4KiB pages. > > config PAGE_SIZE_8KB > bool "8KiB pages" > depends on HAVE_PAGE_SIZE_8KB > help > This option is the only supported page size on a few older > processors, and can be slightly faster than 4KiB pages. > > config PAGE_SIZE_16KB > bool "16KiB pages" > depends on HAVE_PAGE_SIZE_16KB > help > This option is usually a good compromise between memory > consumption and performance for typical desktop and server > workloads, often saving a level of page table lookups compared > to 4KB pages as well as reducing TLB pressure and overhead of > per-page operations in the kernel at the expense of a larger > page cache. > > config PAGE_SIZE_32KB > bool "32KiB pages" > depends on HAVE_PAGE_SIZE_32KB > Using 32KiB page size will result in slightly higher performance > kernel at the price of higher memory consumption compared to > 16KiB pages. This option is available only on cnMIPS cores. > Note that you will need a suitable Linux distribution to > support this. > > config PAGE_SIZE_64KB > bool "64KiB pages" > depends on HAVE_PAGE_SIZE_64KB > Using 64KiB page size will result in slightly higher performance > kernel at the price of much higher memory consumption compared to > 4KiB or 16KiB pages. > This is not suitable for general-purpose workloads but the > better performance may be worth the cost for certain types of > supercomputing or database applications that work mostly with > large in-memory data rather than small files. > > config PAGE_SIZE_256KB > bool "256KiB pages" > depends on HAVE_PAGE_SIZE_256KB > help > 256KB pages have little practical value due to their extreme > memory usage. For 256K pages, powerpc has the following help. I think you should have it too: The kernel will only be able to run applications that have been compiled with '-zmax-page-size' set to 256K (the default is 64K) using binutils later than 2.17.50.0.3, or by patching the ELF_MAXPAGESIZE definition from 0x10000 to 0x40000 in older versions.
