On Wed, Jul 24, 2024 at 2:46 AM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, 18 Jul 2024 20:26:11 +0000 Pasha Tatashin <pasha.tatashin@xxxxxxxxxx> wrote: > > > As part of the dynamic kernel stack project, we need to know the amount > > of data that can be saved by reducing the default kernel stack size [1]. > > > > Provide a kernel stack usage histogram to aid in optimizing kernel stack > > sizes and minimizing memory waste in large-scale environments. The > > histogram divides stack usage into power-of-two buckets and reports the > > results in /proc/vmstat. This information is especially valuable in > > environments with millions of machines, where even small optimizations > > can have a significant impact. > > x86_64 allmodconfig: > > In file included from <command-line>: > In function 'init_memcg_events', > inlined from 'mem_cgroup_css_alloc' at mm/memcontrol.c:3616:3: > ././include/linux/compiler_types.h:510:45: error: call to '__compiletime_assert_2305' declared with attribute error: BUILD_BUG_ON failed: NR_VM_EVENT_ITEMS >= S8_MAX > 510 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > | ^ > ././include/linux/compiler_types.h:491:25: note: in definition of macro '__compiletime_assert' > 491 | prefix ## suffix(); \ > | ^~~~~~ > ././include/linux/compiler_types.h:510:9: note: in expansion of macro '_compiletime_assert' > 510 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > | ^~~~~~~~~~~~~~~~~~~ > ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > | ^~~~~~~~~~~~~~~~~~ > ./include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG' > 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) > | ^~~~~~~~~~~~~~~~ > mm/memcontrol.c:444:9: note: in expansion of macro 'BUILD_BUG_ON' > 444 | BUILD_BUG_ON(NR_VM_EVENT_ITEMS >= S8_MAX); > | ^~~~~~~~~~~~ > > This looks legitimate - is it time to switch to int16_t? I am looking into this, and will also uninline stack_not_used() and kstack_histogram() as discussed earlier in the thread. Pasha
