Update generated RST

src/vmod_slash.man.rst

@@ -269,9 +269,11 @@ memory overhead.
 The *size* argument will be rounded down to a multiple of the
 (possibly rounded) *minpage* argument.
 
-In addition to the configured memory, approximately 1 / ( *minpage* *
-8) bytes are required for metadata (bitmaps). For the default
-*minpage* of 64 Bytes, this amounts to approximately 0.2%.
+Besides the configured memory size, approximately 1 / ( *minpage* *
+4) of it is additionally required for metadata (bitmaps) in the
+varnish home directory and in memory. For the default *minpage* of 64
+Bytes, this amounts to approximately 0.4%. The actual figure is output
+at startup as ``buddy: metadata (bitmap) size``.
 
 This storage can *not* be used via ``storage.``\ *<name>*.
 
@@ -448,6 +450,13 @@ On Linux, the memory cache will be allocated from huge pages, if
 available and if *memsize* is larger than a huge page. *memsize* will
 then be rounded up to a multiple of the respective huge page size.
 
+Besides the configured memory cache size, approximately 1 / 256 (0.4%)
+of *memsize* plus 1 / 16384 (0.006%) of *dsksize* will be required in
+the varnish home directory and in memory. For example, for
+``dsksize=1t`` and ``memsize=1g``, this amounts to roughly 70MB. The
+actual figures are output at startup as ``fellow: metadata (bitmap)
+memory``.
+
 *objsize_hint* (default 256KB) is used to sanity check *memsize* in
 relation to *dsksize*. It should be set to a value lower than the
 average object size (actual or expected). If *memsize* is configured
@@ -870,7 +879,9 @@ FELLOW KNOWN ISSUES
 * On Linux with ``io_uring``, by default, `fellow` registers all of
   the memory cache as buffers using
   :ref:`io_uring_register_buffers(3)` to achieve optimal performance
-  at runtime, if supported by the system.
+  at runtime, if supported by the system. Where supported, this
+  enables *zero-copy* IO, where the hardware performs DMA directly
+  into the `fellow` memory cache.
 
   Buffer registrations happen in multiple threads in parallel, one for
   each io ring.
@@ -890,6 +901,9 @@ FELLOW KNOWN ISSUES
   registration is forced to be done as serial, syncronous registration
   operations.
 
+  Note that even with registered buffers, ``io_uring`` has nothing to
+  do with how the `fellow` memory cache and LRU on it work.
+
 * If initialization takes longer than the :ref:`varnishd(1)`
   ``cli_timeout``, it might not come up properly in that it does not
   accept connections after finishing storage initialization. To avoid