Messages in this thread | | | Date | Sat, 10 Sep 2022 18:06:55 +0200 | From | "Arnd Bergmann" <> | Subject | Re: [PATCH V4 8/8] riscv: Add config of thread stack size |
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On Sat, Sep 10, 2022, at 2:52 PM, Guo Ren wrote: > On Thu, Sep 8, 2022 at 3:37 PM Arnd Bergmann <arnd@arndb.de> wrote: >> On Thu, Sep 8, 2022, at 4:25 AM, guoren@kernel.org wrote: >> > From: Guo Ren <guoren@linux.alibaba.com> >> - 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?
> /* 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
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