DOC: tune: explain the origin of block size for ssl.cachesize

A user could eventually ask himself where those 200 bytes block size are
coming from. This patch tries to better explain the origin in case
people are curious or want to double check the reality.

Signed-off-by: William Dauchy <wdauchy@gmail.com>

diff --git a/doc/configuration.txt b/doc/configuration.txt
index 6856463f3e5ea61e821244284968c5b05c00a112..b30b52f5161237df01e77a0c41d8edd544cc859f 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -2520,16 +2520,17 @@ tune.sndbuf.server <number>
 
 tune.ssl.cachesize <number>
   Sets the size of the global SSL session cache, in a number of blocks. A block
-  is large enough to contain an encoded session without peer certificate.
-  An encoded session with peer certificate is stored in multiple blocks
-  depending on the size of the peer certificate. A block uses approximately
-  200 bytes of memory. The default value may be forced at build time, otherwise
-  defaults to 20000. When the cache is full, the most idle entries are purged
-  and reassigned. Higher values reduce the occurrence of such a purge, hence
-  the number of CPU-intensive SSL handshakes by ensuring that all users keep
-  their session as long as possible. All entries are pre-allocated upon startup
-  and are shared between all processes if "nbproc" is greater than 1. Setting
-  this value to 0 disables the SSL session cache.
+  is large enough to contain an encoded session without peer certificate.  An
+  encoded session with peer certificate is stored in multiple blocks depending
+  on the size of the peer certificate. A block uses approximately 200 bytes of
+  memory (based on `sizeof(struct sh_ssl_sess_hdr) + SHSESS_BLOCK_MIN_SIZE`
+  calculation used for `shctx_init` function). The default value may be forced
+  at build time, otherwise defaults to 20000. When the cache is full, the most
+  idle entries are purged and reassigned. Higher values reduce the occurrence
+  of such a purge, hence the number of CPU-intensive SSL handshakes by ensuring
+  that all users keep their session as long as possible. All entries are
+  pre-allocated upon startup and are shared between all processes if "nbproc"
+  is greater than 1. Setting this value to 0 disables the SSL session cache.
 
 tune.ssl.force-private-cache
   This option disables SSL session cache sharing between all processes. It