* [PATCH] doc: note MALLOC_MMAP_THRESHOLD_ as a potential workaround
@ 2024-04-15 19:50 Eric Wong
0 siblings, 0 replies; only message in thread
From: Eric Wong @ 2024-04-15 19:50 UTC (permalink / raw)
To: meta
Large string processing + concurrency + caching/memoization
really brings out the worst in glibc malloc :<
---
Documentation/public-inbox-tuning.pod | 5 ++++-
examples/public-inbox-netd@.service | 5 ++++-
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/Documentation/public-inbox-tuning.pod b/Documentation/public-inbox-tuning.pod
index 73246144..7d0690b4 100644
--- a/Documentation/public-inbox-tuning.pod
+++ b/Documentation/public-inbox-tuning.pod
@@ -165,8 +165,11 @@ 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.
-jemalloc (tested as an LD_PRELOAD on GNU/Linux) appears to reduce
+jemalloc (tested as an LD_PRELOAD on GNU/Linux) reduces
overall fragmentation compared to glibc malloc in long-lived processes.
+glibc malloc users may try setting C<MALLOC_MMAP_THRESHOLD_> to a lower
+value (e.g. 131072) but that may require increasing the
+C<sys.vm.max_map_count> sysctl.
=head2 Other OS tuning knobs
diff --git a/examples/public-inbox-netd@.service b/examples/public-inbox-netd@.service
index 83d2e995..7437f086 100644
--- a/examples/public-inbox-netd@.service
+++ b/examples/public-inbox-netd@.service
@@ -12,8 +12,11 @@ Wants = public-inbox-netd.socket
After = public-inbox-netd.socket
[Service]
-# An LD_PRELOAD for libjemalloc can be added here. It currently seems
+# An LD_PRELOAD for libjemalloc can be added here. It is
# more resistant to fragmentation in long-lived daemons than glibc.
+# If you're unable to use jemalloc, setting MALLOC_MMAP_THRESHOLD_
+# to a lower value (e.g. 131072) but that may also require increasing
+# the sys.vm.max_map_count sysctl.
Environment = PI_CONFIG=/home/pi/.public-inbox/config \
PATH=/usr/local/bin:/usr/bin:/bin \
TZ=UTC \
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2024-04-15 19:50 [PATCH] doc: note MALLOC_MMAP_THRESHOLD_ as a potential workaround Eric Wong
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