From da655a1859744deec9f558effa5c9981ef5fd6d3 Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Tue, 30 Apr 2024 19:14:13 +0100
Subject: [PATCH] Reduce default concurrency for musl thread over-subscription

https://github.com/lovell/sharp-libvips/issues/229
---
 docs/changelog.md | 2 ++
 lib/utility.js    | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/docs/changelog.md b/docs/changelog.md
index 1b07a15b2..2df84e5cb 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -8,6 +8,8 @@ Requires libvips v8.15.2
 
 * Remove experimental status from `pipelineColourspace`.
 
+* Reduce default concurrency when musl thread over-subscription detected.
+
 * TypeScript: add missing definitions for `OverlayOptions`.
   [#4048](https://github.com/lovell/sharp/pull/4048)
   [@ike-gg](https://github.com/ike-gg)
diff --git a/lib/utility.js b/lib/utility.js
index 3af1b69ac..32738a635 100644
--- a/lib/utility.js
+++ b/lib/utility.js
@@ -153,6 +153,9 @@ function concurrency (concurrency) {
 if (detectLibc.familySync() === detectLibc.GLIBC && !sharp._isUsingJemalloc()) {
   // Reduce default concurrency to 1 when using glibc memory allocator
   sharp.concurrency(1);
+} else if (detectLibc.familySync() === detectLibc.MUSL && sharp.concurrency() === 1024) {
+  // Reduce default concurrency when musl thread over-subscription detected
+  sharp.concurrency(require('node:os').availableParallelism());
 }
 
 /**