docs/vm: clarify overcommit amount sysctl behavior

Documentation/vm/overcommit-accounting.rst says that the overcommit
amount can be set via vm.overcommit_ratio and vm.overcommit_kbytes.

Add a clarification that those only take effect in overcommit handling
mode 2 ("Don't overcommit"), i.e. they do not act as an "additional"
limit that is always enforced.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20211211194159.3137362-1-anssi.hannula@iki.fi
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/vm/overcommit-accounting.rst b/Documentation/vm/overcommit-accounting.rst
index 0dd54bb..1addb0c 100644 (file)
--- a/Documentation/vm/overcommit-accounting.rst
+++ b/Documentation/vm/overcommit-accounting.rst
@@ -34,7 +34,8 @@ The Linux kernel supports the following overcommit handling modes
 The overcommit policy is set via the sysctl ``vm.overcommit_memory``.
 
 The overcommit amount can be set via ``vm.overcommit_ratio`` (percentage)
-or ``vm.overcommit_kbytes`` (absolute value).
+or ``vm.overcommit_kbytes`` (absolute value). These only have an effect
+when ``vm.overcommit_memory`` is set to 2.
 
 The current overcommit limit and amount committed are viewable in
 ``/proc/meminfo`` as CommitLimit and Committed_AS respectively.