openwrt/tools/squashfs4/patches/003-Only-use-available-CPUs.patch

From bc8e655a420d2f62bb0597947e96dce7b4d3fb36 Mon Sep 17 00:00:00 2001
From: Wessel Dankers <wsl@fruit.je>
Date: Sun, 30 Oct 2022 19:29:28 +0100
Subject: [PATCH] Only use available CPUs

Not all online CPUs may be available for the current process,
especially when CPU affinity is involved. In such cases too many
threads will be created, which will then compete unnecessarily
for CPU time.

Use sched_getaffinity() to determine the correct number of threads
to create.
---
 squashfs-tools/mksquashfs.c | 16 ++++++++++++----
 squashfs-tools/unsquashfs.c | 13 ++++++++++---
 2 files changed, 22 insertions(+), 7 deletions(-)

--- a/squashfs-tools/mksquashfs.c
+++ b/squashfs-tools/mksquashfs.c
@@ -52,7 +52,9 @@
 #include <ctype.h>
 #include <sys/sysinfo.h>
 
-#ifndef linux
+#ifdef linux
+#include <sched.h>
+#else
 #include <sys/sysctl.h>
 #endif
 
@@ -5079,7 +5081,15 @@ static void initialise_threads(int readq
 		BAD_ERROR("Failed to set signal mask in intialise_threads\n");
 
 	if(processors == -1) {
-#ifndef linux
+#ifdef linux
+		cpu_set_t cpu_set;
+		CPU_ZERO(&cpu_set);
+
+		if(sched_getaffinity(0, sizeof cpu_set, &cpu_set) == -1)
+			processors = sysconf(_SC_NPROCESSORS_ONLN);
+		else
+			processors = CPU_COUNT(&cpu_set);
+#else
 		int mib[2];
 		size_t len = sizeof(processors);
 
@@ -5096,8 +5106,6 @@ static void initialise_threads(int readq
 			ERROR_EXIT("  Defaulting to 1\n");
 			processors = 1;
 		}
-#else
-		processors = sysconf(_SC_NPROCESSORS_ONLN);
 #endif
 	}
 
--- a/squashfs-tools/unsquashfs.c
+++ b/squashfs-tools/unsquashfs.c
@@ -33,6 +33,7 @@
 #include "fnmatch_compat.h"
 
 #ifdef __linux__
+#include <sched.h>
 #include <sys/sysinfo.h>
 #include <sys/sysmacros.h>
 #elif defined __FreeBSD__
@@ -2719,7 +2720,15 @@ void initialise_threads(int fragment_buf
 	}
 
 	if(processors == -1) {
-#ifndef linux
+#ifdef linux
+		cpu_set_t cpu_set;
+		CPU_ZERO(&cpu_set);
+
+		if(sched_getaffinity(0, sizeof cpu_set, &cpu_set) == -1)
+			processors = sysconf(_SC_NPROCESSORS_ONLN);
+		else
+			processors = CPU_COUNT(&cpu_set);
+#else
 		int mib[2];
 		size_t len = sizeof(processors);
 
@@ -2735,8 +2744,6 @@ void initialise_threads(int fragment_buf
 				"Defaulting to 1\n");
 			processors = 1;
 		}
-#else
-		processors = sysconf(_SC_NPROCESSORS_ONLN);
 #endif
 	}