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Diffstat (limited to 'Documentation/public-inbox-tuning.pod')
| -rw-r--r-- | Documentation/public-inbox-tuning.pod | 42 |
1 files changed, 36 insertions, 6 deletions
diff --git a/Documentation/public-inbox-tuning.pod b/Documentation/public-inbox-tuning.pod index 53668ecc..892ee0f2 100644 --- a/Documentation/public-inbox-tuning.pod +++ b/Documentation/public-inbox-tuning.pod @@ -42,6 +42,14 @@ Other OS tuning knobs Scalability to many inboxes +=item 9 + +public-inbox-cindex --join performance + +=item 10 + +public-inbox-clone with shared object stores + =back =head2 New inboxes: public-inbox-init -V2 @@ -79,8 +87,8 @@ RAM. Attempts to parallelize random I/O on HDDs leads to pathological slowdowns as inboxes grow. While C<-V2> introduced Xapian shards as a parallelization -mechanism for SSDs; enabling C<publicInbox.indexSequentialShard> -repurposes sharding as mechanism to reduce the kernel page cache +mechanism for SSDs, enabling C<publicInbox.indexSequentialShard> +repurposes sharding as a mechanism to reduce the kernel page cache footprint when indexing on HDDs. Initializing a mirror with a high C<--jobs> count to create more @@ -108,7 +116,7 @@ indices on btrfs to achieve acceptable performance (even on SSD). Disabling copy-on-write also disables checksumming, thus C<raid1> (or higher) configurations may be corrupt after unsafe shutdowns. -Fortunately, these SQLite and Xapian indices are designed to +Fortunately, these SQLite and Xapian indices are designed to be recoverable from git if missing. Disabling CoW does not prevent all fragmentation. Large values @@ -125,7 +133,7 @@ C<btrfs filesystem defragment -fr $INBOX_DIR> may be necessary. Large filesystems benefit significantly from the C<space_cache=v2> mount option documented in L<btrfs(5)>. -Older, non-CoW filesystems are generally work well out-of-the-box +Older, non-CoW filesystems generally work well out of the box for our Xapian and SQLite indices. =head2 Performance on solid state drives @@ -152,9 +160,16 @@ C<LimitNOFILE=> in L<systemd.exec(5)>) may need to be raised to accommodate many concurrent clients. Transport Layer Security (IMAPS, NNTPS, or via STARTTLS) significantly -increases memory use of client sockets, sure to account for that in +increases memory use of client sockets, be sure to account for that in capacity planning. +Bursts of small object allocations late in process life contribute to +fragmentation of the heap due to arenas (slabs) used internally by Perl. +glibc malloc users should use C<MALLOC_MMAP_THRESHOLD_=131072> to reduce +fragmentation from the sliding mmap window. jemalloc (tested as an +LD_PRELOAD on GNU/Linux) also reduces fragmentation compared to an +unconfigured glibc malloc in long-lived processes. + =head2 Other OS tuning knobs Linux users: the C<sys.vm.max_map_count> sysctl may need to be increased if @@ -168,13 +183,28 @@ Other OSes may have similar tuning knobs (patches appreciated). L<public-inbox-extindex(1)> allows any number of public-inboxes to share the same Xapian indices. -git 2.33+ startup time is orders-of-magnitude faster and uses +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<public-inbox-extindex(1)>. Frequent packing (via L<git-gc(1)>) both improves performance and reduces the need to increase C<sys.vm.max_map_count>. +=head2 public-inbox-cindex --join performance + +A C++ compiler and the Xapian development files makes C<--join> or +C<--join=aggressive> orders of magnitude faster in L<public-inbox-cindex(1)>. +On Debian-based systems this is C<libxapian-dev>. RPM-based distros have +these in C<xapian-core-devel> or C<xapian14-core-libs>. *BSDs typically +package development files together with runtime libraries, so the C<xapian> +or C<xapian-core> package will already have the development files. + +=head2 public-inbox-clone with shared object stores + +When mirroring manifests with many forks using the same objstore, +git 2.41+ is highly recommended for performance as we automatically +use the C<fetch.hideRefs> feature to speed up negotiation. + =head1 CONTACT Feedback encouraged via plain-text mail to L<mailto:meta@public-inbox.org> |