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[PATCH] BZ #18185: Wrong processor count for L2 cache sharing on Silvermont and Knights Landing


Hi,

Silvermont and Knights Landing have a modular system design with two cores
sharing an L2 cache.  If more than 2 cores are detected to shared L2 cache,
it should be adjusted for Silvermont and Knights Landing.

I am planning to check it in shortly.

H.J.
---
	[BZ #18185]
	* sysdeps/x86_64/cacheinfo.c (init_cacheinfo): Limit threads
	sharing L2 cache to 2 for Silvermont/Knights Landing.
---
 sysdeps/x86_64/cacheinfo.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/sysdeps/x86_64/cacheinfo.c b/sysdeps/x86_64/cacheinfo.c
index f1cbf50..b99fb9a 100644
--- a/sysdeps/x86_64/cacheinfo.c
+++ b/sysdeps/x86_64/cacheinfo.c
@@ -585,6 +585,10 @@ init_cacheinfo (void)
       __cpuid (1, eax, ebx_1, ecx, edx);
 #endif
 
+      unsigned int family = (eax >> 8) & 0x0f;
+      unsigned int model = (eax >> 4) & 0x0f;
+      unsigned int extended_model = (eax >> 12) & 0xf0;
+
 #ifndef DISABLE_PREFERRED_MEMORY_INSTRUCTION
       /* Intel prefers SSSE3 instructions for memory/string routines
 	 if they are available.  */
@@ -647,6 +651,25 @@ init_cacheinfo (void)
 		}
 	    }
 	  threads += 1;
+	  if (threads > 2 && level == 2 && family == 6)
+	    {
+	      model += extended_model;
+	      switch (model)
+		{
+		case 0x57:
+		  /* Knights Landing has L2 cache shared by 2 cores.  */
+		case 0x37:
+		case 0x4a:
+		case 0x4d:
+		case 0x5a:
+		case 0x5d:
+		  /* Silvermont has L2 cache shared by 2 cores.  */
+		  threads = 2;
+		  break;
+		default:
+		  break;
+		}
+	    }
 	}
       else
 	{
-- 
1.9.3


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