On Sun, Sep 11, 2022 at 12:07 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Sat, Sep 10, 2022, at 2:52 PM, Guo Ren wrote: > > On Thu, Sep 8, 2022 at 3:37 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> On Thu, Sep 8, 2022, at 4:25 AM, guoren@xxxxxxxxxx wrote: > >> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > >> - When VMAP_STACK is set, make it possible to select non-power-of-two > >> stack sizes. Most importantly, 12KB should be a really interesting > >> choice as 8KB is probably still not enough for many 64-bit workloads, > >> but 16KB is often more than what you need. You probably don't > >> want to allow 64BIT/8KB without VMAP_STACK anyway since that just > >> makes it really hard to debug, so hiding the option when VMAP_STACK > >> is disabled may also be a good idea. > > I don't want this config to depend on VMAP_STACK. Some D1 chips would > > run with an 8K stack size and !VMAP_STACK. > > That sounds like a really bad idea, why would you want to risk > using such a small stack without CONFIG_VMAP_STACK? > > Are you worried about increased memory usage or something else? The requirement is from [1], and I think disabling CONFIG_VMAP_STACK would be the last step after serious testing. [1] https://www.cnx-software.com/2021/10/25/allwinner-d1s-f133-risc-v-processor-64mb-ddr2/ > > > /* thread information allocation */ > > -#ifdef CONFIG_64BIT > > -#define THREAD_SIZE_ORDER (2 + KASAN_STACK_ORDER) > > -#else > > -#define THREAD_SIZE_ORDER (1 + KASAN_STACK_ORDER) > > -#endif > > +#define THREAD_SIZE_ORDER CONFIG_THREAD_SIZE_ORDER > > #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) > > This doesn't actually allow additional THREAD_SIZE values, as you > still round up to the nearest power of two. > > I think all the non-arch code can deal with non-power-of-2 > sizes, so you'd just need > > #define THREAD_SIZE round_up(CONFIG_THREAD_SIZE, PAGE_SIZE) > > and fix up the risc-v specific code to do the right thing > as well. I now see that THREAD_SIZE_ORDER is not actually > used anywhere with CONFIG_VMAP_STACK, so I suppose that > definition can be skipped, but you still need a THREAD_ALIGN > definition that is a power of two and at least a page larger > than THREAD_SIZE. > > Arnd -- Best Regards Guo Ren
