Currently, userspace has limited visibility into the exact active runtime state of memory allocation profiling and its page extension compression ('sysctl.vm.mem_profiling={0|1|never}[,compressed]'). While reading the sysctl provides basic on/off status, it is currently impossible for userspace to natively determine whether page-tag compression was successfully enabled without scraping dmesg boot logs. Resolve this ambiguity by exposing the active compression state by adding a new read-only sysctl `vm.mem_profiling_compressed` to output the state. v3 change: - Added documentation about the behaviour details of the new sysctl. v2 change: - Moved from displaying the state in /proc/allocinfo to a new read-only sysctl. Signed-off-by: Abhishek Bapat --- Documentation/mm/allocation-profiling.rst | 13 +++++++++++++ mm/alloc_tag.c | 6 ++++++ 2 files changed, 19 insertions(+) diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst index c3a28467955f..3ad1e9aacb9a 100644 --- a/Documentation/mm/allocation-profiling.rst +++ b/Documentation/mm/allocation-profiling.rst @@ -43,6 +43,19 @@ sysctl: warnings produced by allocations made while profiling is disabled and freed when it's enabled. + /proc/sys/vm/mem_profiling_compressed + + 1: Page extension compression is enabled. + + 0: Page extension compression is disabled. + + This control is read-only and reflects the compression status initialized at boot. + Note that, unlike `mem_profiling`, which represents the current state of profiling, + `mem_profiling_compressed` represents the state configured at boot time. Turning off + profiling at runtime will implicitly make this sysctl effectively dormant. However, if + profiling is toggled off and then toggled on again, it will resume with compression + still enabled as long as the value of `mem_profiling_compressed` is 1. + Runtime info: /proc/allocinfo diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c index 52aece27b00e..877068241f06 100644 --- a/mm/alloc_tag.c +++ b/mm/alloc_tag.c @@ -1303,6 +1303,12 @@ static const struct ctl_table memory_allocation_profiling_sysctls[] = { .mode = 0644, .proc_handler = proc_mem_profiling_handler, }, + { + .procname = "mem_profiling_compressed", + .data = &mem_profiling_compressed, + .mode = 0444, + .proc_handler = proc_do_static_key, + }, }; static void __init sysctl_init(void) base-commit: 94f9b3980dd446b56acf1dfed649e9b32a9f3813 -- 2.55.0.508.g3f0d502094-goog