tools/cephfs: document --max-rss usage in first-damage.py

Partially-Fixes: https://tracker.ceph.com/issues/76422
Signed-off-by: Dhairya Parmar <dparmar@redhat.com>

diff --git a/src/tools/cephfs/first-damage.py b/src/tools/cephfs/first-damage.py
index 763ab5af7f66845f2fce8a42c632aada3e4f68c0..02483bba507ce3eda936519242198fb71b8c1a38 100644 (file)
--- a/src/tools/cephfs/first-damage.py
+++ b/src/tools/cephfs/first-damage.py
@@ -23,6 +23,16 @@
 #
 #    cephfs-journal-tool --rank=<fs_name>:0 event recover_dentries summary
 #
+#    NOTE: Large journal sizes can cause the tool's Resident Set Size (RSS) to
+#          spike significantly. To prevent excessive memory consumption, use the
+#          `--max-rss <bytes>` flag to cap the RSS. 
+#
+#          Avoid setting this value too low, as it will severely degrade runtime
+#          performance and prolong recovery. It is best practice to maintain a memory
+#          buffer of at least 30% of the tool's total budget. For example, if 100 GiB
+#          is to be allotted to the tool, cap the RSS at 70 GiB
+#          (`--max-rss 75161927680`).
+#
 # 4b) If all good so far, reset the journal:
 #
 #    cephfs-journal-tool --rank=<fs_name>:0 journal reset --yes-i-really-really-mean-it