From a45cebf11522b3112fba3d682224a232ae5e2e98 Mon Sep 17 00:00:00 2001
From: Andreas Arnez <arnez@linux.ibm.com>
Date: Wed, 12 Dec 2018 19:44:32 +0100
Subject: [PATCH 4/8] Read L1 data cache size from sysconf if possible

The probing of the L1 data cache size is sometimes not reliable.  This can
cause the tuning to yield varying, sub-obtimal results.  But on Linux the
L1 data cache size can usually be retrieved with sysconf instead, which is
faster and more reliable.  Do this whenever possible.
---
 tune/sysinfo/L1CacheSize.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/tune/sysinfo/L1CacheSize.c b/tune/sysinfo/L1CacheSize.c
index e62a273..dffa76e 100644
--- a/tune/sysinfo/L1CacheSize.c
+++ b/tune/sysinfo/L1CacheSize.c
@@ -30,6 +30,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #define REPS 4096
 
@@ -276,7 +277,16 @@ int main(int nargs, char *args[])
       exit(-1);
    }
    if (nargs > 1) MaxSize = atoi(args[1]);
-   L1Size = GetL1Size(MaxSize, 1.08);
+
+#ifdef _SC_LEVEL1_DCACHE_SIZE
+   {
+      long res = sysconf(_SC_LEVEL1_DCACHE_SIZE);
+      L1Size = res > 0 ? (int) (res / 1024) : 0;
+   }
+#endif
+
+   if (!L1Size)
+      L1Size = GetL1Size(MaxSize, 1.08);
    if (!L1Size)
       L1Size = GetL1Size(MaxSize, 1.08);
    if (!L1Size)
-- 
2.23.0