linux-kernel - [PATCH] x86: Intel microcode loader performance improvement

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Message-ID: <20100305174203.GA19638@sgi.com>
Date:	Fri, 5 Mar 2010 11:42:03 -0600
From:	Dimitri Sivanich <sivanich@....com>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: [PATCH] x86: Intel microcode loader performance improvement

We've noticed that on large SGI UV system configurations, running
microcode.ctl can take very long periods of time.  This is due to
the large number of vmalloc/vfree calls made by the Intel
generic_load_microcode() logic.

By reusing allocated space, the following patch reduces the time
to run microcode.ctl on a 1024 cpu system from approximately 80
seconds down to 1 or 2 seconds.

Signed-off-by: Dimitri Sivanich <sivanich@....com>

---

 arch/x86/kernel/microcode_intel.c |   22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

Index: linux/arch/x86/kernel/microcode_intel.c
===================================================================
--- linux.orig/arch/x86/kernel/microcode_intel.c
+++ linux/arch/x86/kernel/microcode_intel.c
@@ -343,10 +343,11 @@ static enum ucode_state generic_load_mic
 				int (*get_ucode_data)(void *, const void *, size_t))
 {
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
-	u8 *ucode_ptr = data, *new_mc = NULL, *mc;
+	u8 *ucode_ptr = data, *new_mc = NULL, *mc = NULL;
 	int new_rev = uci->cpu_sig.rev;
 	unsigned int leftover = size;
 	enum ucode_state state = UCODE_OK;
+	unsigned int curr_mc_size = 0;
 
 	while (leftover) {
 		struct microcode_header_intel mc_header;
@@ -361,9 +362,15 @@ static enum ucode_state generic_load_mic
 			break;
 		}
 
-		mc = vmalloc(mc_size);
-		if (!mc)
-			break;
+		/* For performance reasons, reuse mc area when possible */
+		if (!mc || mc_size > curr_mc_size) {
+			if (mc)
+				vfree(mc);
+			mc = vmalloc(mc_size);
+			if (!mc)
+				break;
+			curr_mc_size = mc_size;
+		}
 
 		if (get_ucode_data(mc, ucode_ptr, mc_size) ||
 		    microcode_sanity_check(mc) < 0) {
@@ -376,13 +383,16 @@ static enum ucode_state generic_load_mic
 				vfree(new_mc);
 			new_rev = mc_header.rev;
 			new_mc  = mc;
-		} else
-			vfree(mc);
+			mc = NULL;	/* trigger new vmalloc */
+		}
 
 		ucode_ptr += mc_size;
 		leftover  -= mc_size;
 	}
 
+	if (mc)
+		vfree(mc);
+
 	if (leftover) {
 		if (new_mc)
 			vfree(new_mc);
--
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