From 78b1c973fba89bc6651ffa16807c40abd38e7bad Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Tue, 25 Aug 2020 10:51:20 +0000 Subject: doc: add some more tuning notes I've learned a thing or three about btrfs in the past few weeks and remembered some old HDD things, too. The Xapian MultiDatabase problem will need to be addressed for 1.7... --- Documentation/public-inbox-init.pod | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'Documentation/public-inbox-init.pod') diff --git a/Documentation/public-inbox-init.pod b/Documentation/public-inbox-init.pod index b25dd1e4..24645045 100644 --- a/Documentation/public-inbox-init.pod +++ b/Documentation/public-inbox-init.pod @@ -86,14 +86,21 @@ Default: unset, no epochs are skipped Control the number of Xapian index shards in a C<-V2> (L) inbox. -It is useful to use a single shard (C<-j1>) for inboxes on +It can be useful to use a single shard (C<-j1>) for inboxes on high-latency storage (e.g. rotational HDD) unless the system has enough RAM to cache 5-10x the size of the git repository. -It is generally not useful to specify higher values than the -default due to contention in the top-level producer process. +Another approach for HDDs is to use the +L option +and many shards, so each shard may fit into the kernel page +cache. Unfortunately, excessive shards slows down read-only +query performance. -Default: the number of online CPUs, up to 4 +For fast storage, it is generally not useful to specify higher +values than the default due to the top-level producer process +being a bottleneck. + +Default: the number of online CPUs, up to 4 (3 shard workers, 1 producer) =item --skip-docdata -- cgit v1.2.3-24-ge0c7