On Mon, Mar 11, 2024 at 3:32 PM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: > > Hi, > > just typos etc. > > On 3/11/24 09:46, Pasha Tatashin wrote: > > The core implementation of dynamic kernel stacks. > > > > ... > > > > > Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx> > > --- > > arch/Kconfig | 34 +++++ > > include/linux/sched.h | 2 +- > > include/linux/sched/task_stack.h | 41 +++++- > > kernel/fork.c | 239 +++++++++++++++++++++++++++++++ > > kernel/sched/core.c | 1 + > > 5 files changed, 315 insertions(+), 2 deletions(-) > > > > diff --git a/arch/Kconfig b/arch/Kconfig > > index a5af0edd3eb8..da3df347b069 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -1241,6 +1241,40 @@ config VMAP_STACK > > backing virtual mappings with real shadow memory, and KASAN_VMALLOC > > must be enabled. > > > > +config HAVE_ARCH_DYNAMIC_STACK > > + def_bool n > > + help > > + An arch should select this symbol if it can support kernel stacks > > + dynamic growth. > > + > > + - Arch must have support for HAVE_ARCH_VMAP_STACK, in order to handle > > + stack related page faults > > stack-related > > > + > > + - Arch must be able to faults from interrupt context. > > fault > > > + - Arch must allows the kernel to handle stack faults gracefully, even > > allow > > > + during interrupt handling. > > + > > + - Exceptions such as no pages available should be handled the same > > handled in the same > > > + in the consitent and predictable way. I.e. the exception should be > > consistent > > > + handled the same as when stack overflow occurs when guard pages are > > + touched with extra information about the allocation error. > > + > > +config DYNAMIC_STACK > > + default y > > + bool "Dynamically grow kernel stacks" > > + depends on THREAD_INFO_IN_TASK > > + depends on HAVE_ARCH_DYNAMIC_STACK > > + depends on VMAP_STACK > > + depends on !KASAN > > + depends on !DEBUG_STACK_USAGE > > + depends on !STACK_GROWSUP > > + help > > + Dynamic kernel stacks allow to save memory on machines with a lot of > > + threads by starting with small stacks, and grow them only when needed. > > + On workloads where most of the stack depth do not reach over one page > > does > > > + the memory saving can be subsentantial. The feature requires virtually > > substantial. > > > + mapped kernel stacks in order to handle page faults. > > + > > config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET > > def_bool n > > help > > > > > +/* > > + * This flag is used to pass information from fault handler to refill about > > + * which pages were allocated, and should be charged to memcg. > > + */ > > +#define DYNAMIC_STACK_PAGE_AQUIRED_FLAG 0x1 > > ACQUIRED > please Thank you Randy, I will address your comments in my next revision. Pasha > > > > -- > #Randy
