From: bellard <bellard>
Date: Tue, 2 May 2006 22:18:28 +0000 (+0000)
Subject: performance boost (on P4 hosts at least, rdtsc is a _very_ bad random generator)
X-Git-Tag: release_0_8_1~5
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=716417c76680ba9d356622aae70733ee3cdd17f9;p=xenclient%2Fioemu.git

performance boost (on P4 hosts at least, rdtsc is a _very_ bad random generator)
---

diff --git a/hw/mips_r4k.c b/hw/mips_r4k.c
index 6b6b6cb3..0cb11683 100644
--- a/hw/mips_r4k.c
+++ b/hw/mips_r4k.c
@@ -27,11 +27,14 @@ void cpu_mips_irqctrl_init (void)
 {
 }
 
+/* XXX: do not use a global */
 uint32_t cpu_mips_get_random (CPUState *env)
 {
-    uint32_t now = qemu_get_clock(vm_clock);
-
-    return now % (MIPS_TLB_NB - env->CP0_Wired) + env->CP0_Wired;
+    static uint32_t seed = 0;
+    uint32_t idx;
+    seed = seed * 314159 + 1;
+    idx = (seed >> 16) % (MIPS_TLB_NB - env->CP0_Wired) + env->CP0_Wired;
+    return idx;
 }
 
 /* MIPS R4K timer */