dcache-xroot: increase server-side frame size to 8 MiB

Motivation:

Currently, the frame size with which the server serves up responses
to read requests is 1/4 of what native xroot uses (8 MiB).

There does not seem to be any justification to use the smaller size;
the larger size also gets us better performance.

Modification:

Increase the default value of the frame property to 8 MiB.

Result:

Better performance.

Target: master
Requires-notes: yes
Requires-book: no
Patch: https://rb.dcache.org/r/13118/
Acked-by: Marina

modules/dcache/src/main/resources/org/dcache/pool/classic/pool.xml

@@ -373,6 +373,7 @@
       <property name="connectTimeoutUnit" value="${pool.mover.xrootd.timeout.connect.unit}"/>
       <property name="maxFrameSize" value="${pool.mover.xrootd.frame-size}"/>
       <property name="tpcClientChunkSize" value="#{ T(org.dcache.util.ByteSizeParser).using( T(org.dcache.util.ByteUnits).isoPrefix()).parse('${pool.mover.xrootd.tpc-client-chunk-size}') }"/>
+      <property name="maxFrameSize" value="#{ T(org.dcache.util.ByteSizeParser).using( T(org.dcache.util.ByteUnits).isoPrefix()).parse('${pool.mover.xrootd.frame-size}') }"/>
       <property name="readReconnectTimeout" value="${pool.mover.xrootd.read-reconnect-timeout}"/>
       <property name="readReconnectTimeoutUnit" value="${pool.mover.xrootd.read-reconnect-timeout.unit}"/>
       <property name="accessLogPlugins">

skel/share/defaults/pool.properties

@@ -309,7 +309,7 @@ pool.mover.xrootd.threads = 20
 #
 #   Specified in bytes.
 #
-pool.mover.xrootd.frame-size = 2097152
+pool.mover.xrootd.frame-size = 8 MiB
 
 #  ---- xroot plugins
 #