doc: tuning: add a note about Linux sys.vm.max_map_count

git tends to die when mmap(2) fails on this limit, so let
users know about it.  Perhaps git could gracefully fallback.

diff --git a/Documentation/public-inbox-tuning.pod b/Documentation/public-inbox-tuning.pod
index 58937f732dd157dd6be993ba01e7172337131041..67316fb11109b4071197a2db9788dc254eb9a1d0 100644 (file)
--- a/Documentation/public-inbox-tuning.pod
+++ b/Documentation/public-inbox-tuning.pod
@@ -34,6 +34,10 @@ Performance on solid state drives
 
 Read-only daemons
 
 
 Read-only daemons
 

+=item 7
+
+Other OS tuning knobs
+

 =back
 
 =head2 New inboxes: public-inbox-init -V2
 =back
 
 =head2 New inboxes: public-inbox-init -V2


@@ -148,6 +152,15 @@ Transport Layer Security (IMAPS, NNTPS, or via STARTTLS) significantly
 increases memory use of client sockets, sure to account for that in
 capacity planning.
 
 increases memory use of client sockets, sure to account for that in
 capacity planning.
 

+=head2 Other OS tuning knobs
+
+Linux users: the C<sys.vm.max_map_count> sysctl may need to be increased if
+handling thousands of inboxes (with L<public-inbox-extindex(1)>) to avoid
+out-of-memory errors from git.
+
+Other OSes may have similar tuning knobs (patches appreciated).
+
+

 =head1 CONTACT
 
 Feedback encouraged via plain-text mail to L<mailto:meta@public-inbox.org>
 =head1 CONTACT
 
 Feedback encouraged via plain-text mail to L<mailto:meta@public-inbox.org>