X-Git-Url: http://www.git.stargrave.org/?a=blobdiff_plain;f=Documentation%2Fpublic-inbox-tuning.pod;h=53668eccb7cb85a7a7c0f6149c0c8c54189614e2;hb=0ae89efce11e1e3b10a067c61c5b4cde30fa2b3b;hp=b4e7698bcca975a972921216128d74225cb222f9;hpb=7cca148aa220d2c747f6487bd8987e0e36db0367;p=public-inbox.git diff --git a/Documentation/public-inbox-tuning.pod b/Documentation/public-inbox-tuning.pod index b4e7698b..53668ecc 100644 --- a/Documentation/public-inbox-tuning.pod +++ b/Documentation/public-inbox-tuning.pod @@ -16,7 +16,7 @@ New inboxes: public-inbox-init -V2 =item 2 -Process spawning +Optional Inline::C use =item 3 @@ -34,6 +34,14 @@ Performance on solid state drives Read-only daemons +=item 7 + +Other OS tuning knobs + +=item 8 + +Scalability to many inboxes + =back =head2 New inboxes: public-inbox-init -V2 @@ -42,7 +50,7 @@ If you're starting a new inbox (and not mirroring an existing one), the L<-V2|public-inbox-v2-format(5)> requires L, but is orders of magnitude more scalable than the original C<-V1> format. -=head2 Process spawning +=head2 Optional Inline::C use Our optional use of L speeds up subprocess spawning from large daemon processes. @@ -52,9 +60,17 @@ environment variable to point to a writable directory, or create C<~/.cache/public-inbox/inline-c> for any user(s) running public-inbox processes. +If libgit2 development files are installed and L +is enabled (described above), per-inbox C +processes are replaced with a single L process running +C in read-only daemons. libgit2 use +will be available in public-inbox 1.7.0+ + More (optional) L use will be introduced in the future to lower memory use and improve scalability. +Note: L is required for L, but not public-inbox-* + =head2 Performance on rotational hard disk drives Random I/O performance is poor on rotational HDDs. Xapian indexing @@ -74,7 +90,7 @@ sharding imposes a performance penalty for read-only queries. Users with large amounts of RAM are advised to set a large value for C as documented in -L. +L. C users on Linux 4.0+ are advised to try the C<--perf-same_cpu_crypt> C<--perf-submit_from_crypt_cpus> @@ -95,7 +111,9 @@ Disabling copy-on-write also disables checksumming, thus C Fortunately, these SQLite and Xapian indices are designed to recoverable from git if missing. -Disabling CoW does not prevent all fragmentation. +Disabling CoW does not prevent all fragmentation. Large values +of C also limit fragmentation during +the initial index. Avoid snapshotting subvolumes containing Xapian and/or SQLite indices. Snapshots use CoW despite our efforts to disable it, resulting @@ -137,6 +155,26 @@ Transport Layer Security (IMAPS, NNTPS, or via STARTTLS) significantly increases memory use of client sockets, sure to account for that in capacity planning. +=head2 Other OS tuning knobs + +Linux users: the C sysctl may need to be increased if +handling thousands of inboxes (with L) to avoid +out-of-memory errors from git. + +Other OSes may have similar tuning knobs (patches appreciated). + +=head2 Scalability to many inboxes + +L allows any number of public-inboxes +to share the same Xapian indices. + +git 2.33+ startup time is orders-of-magnitude faster and uses +less memory when dealing with thousands of alternates required +for thousands of inboxes with L. + +Frequent packing (via L) both improves performance +and reduces the need to increase C. + =head1 CONTACT Feedback encouraged via plain-text mail to L @@ -145,10 +183,10 @@ Information for *BSDs and non-traditional filesystems especially welcome. Our archives are hosted at L, -L, and other places +L, and other places =head1 COPYRIGHT -Copyright 2020 all contributors L +Copyright all contributors L License: AGPL-3.0+ L