Add the LIMITATIONS docs.

README.rst

@@ -509,7 +509,21 @@ See `INSTALL.rst <INSTALL.rst>`_ in the source repository.
 LIMITATIONS
 ===========
 
-XXX ...
+Memory and CPU usage for compression and decompression is largely
+driven by the choice of parameters for the brotli algorithm. If you
+need to limit resource consumption, consider using custom filters, and
+adjusting the parameters as needed.
+
+Memory used by the VFP, such as the temporary internal buffer and
+other internal structures, is allocated from the heap, and hence is
+limited by available virtual memory.
+
+As noted above, brotli compression does not work together with Edge
+Side Includes, or ESI includes, as gzip support does for standard
+Varnish. If you are using ESI, then brotli-compressed backend
+responses will have to be decompressed on fetch. Without any special
+measures taken in VCL, client responses with ESI-included content will
+have to be delivered uncompressed.
 
 SEE ALSO
 ========

src/vfp_brotli.vcc

@@ -473,7 +473,21 @@ See `INSTALL.rst <INSTALL.rst>`_ in the source repository.
 LIMITATIONS
 ===========
 
-XXX ...
+Memory and CPU usage for compression and decompression is largely
+driven by the choice of parameters for the brotli algorithm. If you
+need to limit resource consumption, consider using custom filters, and
+adjusting the parameters as needed.
+
+Memory used by the VFP, such as the temporary internal buffer and
+other internal structures, is allocated from the heap, and hence is
+limited by available virtual memory.
+
+As noted above, brotli compression does not work together with Edge
+Side Includes, or ESI includes, as gzip support does for standard
+Varnish. If you are using ESI, then brotli-compressed backend
+responses will have to be decompressed on fetch. Without any special
+measures taken in VCL, client responses with ESI-included content will
+have to be delivered uncompressed.
 
 SEE ALSO
 ========