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alloc_tag: expose boot-time compression configuration

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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.

Add a new read-only sysctl representing how compression was configured
at boot time.

Link: https://lore.kernel.org/c795f8089f82841e8a6e00d7ca286da2b23aeb7b.1785950530.git.abhishekbapat@google.com
Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Hao Ge <hao.ge@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Abhishek Bapat 2026-08-05 17:29:52 +00:00 committed by Andrew Morton
parent bb3e3c5c2d
commit afff109c2f
2 changed files with 17 additions and 0 deletions
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11
Documentation/mm/allocation-profiling.rst
View File

@ -43,6 +43,17 @@ sysctl:
warnings produced by allocations made while profiling is disabled and freed
when it's enabled.
/proc/sys/vm/mem_profiling_compressed
1: Page alloc tag compression is enabled.
0: Page alloc tag compression is disabled.
This reflects a static boot-time configuration of how page allocation tags are
stored (in page flags when compression is enabled and in page_ext when disabled).
Toggling ``mem_profiling`` at runtime does not change the state of
``mem_profiling_compressed``.
Runtime info:
/proc/allocinfo

6
mm/alloc_tag.c
View File

@ -961,6 +961,12 @@ 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)