doc/dev/crimson.rst: update with stuff related to seastar options

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/doc/dev/crimson.rst b/doc/dev/crimson.rst
index 4d5683876c36b6df699a1dfa9409c1a5836ba000..29c72001428f893c76cdb03082a06262b45f78b0 100644 (file)
--- a/doc/dev/crimson.rst
+++ b/doc/dev/crimson.rst
@@ -92,9 +92,19 @@ using ``vstart.sh``,
 ``--redirect-output``
     redirect the stdout and stderr of service to ``out/$type.$num.stdout``.
 
+``--osd-args``
+    pass extra command line options to crimson-osd or ceph-osd. It's quite
+    useful for passing Seastar options to crimson-osd.
+
 So, a typical command to start a single-crimson-node cluster is::
 
-  MGR=1 MON=1 OSD=1 MDS=0 RGW=0 ../src/vstart.sh -n -x --without-dashboard --memstore --crimson --nodaemon --redirect-output
+  MGR=1 MON=1 OSD=1 MDS=0 RGW=0 ../src/vstart.sh -n -x --without-dashboard --memstore \
+    --crimson --nodaemon --redirect-output \
+    --osd-args "--memory 4G --smp 1 --cpuset 0"
+
+Where we assign 4 GiB memory, a single thread running on core-0 to crimson-osd.
+Please refer ``crimson-osd --help-seastar`` for more Seastar specific command
+line options.
 
 You could stop the vstart cluster using::