I have been developing a driver for an audio card and encountered a problem which I have duplicated in the test code below. My problem is that when trying to profile a section of code in a kernel module I get erratic results. My cycle counts are sometimes 73xxx cycles more that I expect them to be. Does anyone know what could be causing this? Thanks in Advance, Chris K Cockrum iBiquity Digital Corp. http://www.ibiquity.com Running Linux 2.4.0 on a Tyan Tiger Dual 800MHz Motherboard w/133MHz Bus #include <linux/kernel.h> #include <linux/module.h> #include <linux/sched.h> #include <asm/smplock.h> /* Declare Spinlock */ spinlock_t testlock; int init_module(void) { unsigned long long starttime,stoptime; unsigned int lockflags,n,tempval=20000; spin_lock_init(&testlock); for (n=0;n<40;n++) { spin_lock_irqsave(&testlock,lockflags); /* Clear Interrupt Flag */ __asm__ __volatile__ ("cli"); /* Get CPU Clock */ __asm__ __volatile__ ("rdtsc\n\t" \ "movl %%eax, (%%ecx)\n\t" \ "movl %%edx, 4(%%ecx)"\ ::"c" (&starttime)); /* Waste Time-Register Moves Looped tempval Times */ __asm__ __volatile__ ("loop: movl %%ecx,%%eax\t\n" \ " decl %%ecx\t\n" \ " jnz loop" \ :: "c" (tempval) : "%eax"); /* Get CPU Clock */ __asm__ __volatile__ ("rdtsc\n\t" \ "movl %%eax, (%%ecx)\n\t" \ "movl %%edx, 4(%%ecx)"\ ::"c" (&stoptime)); spin_unlock_irqrestore(&testlock,lockflags); printk(KERN_DEBUG "Test: 0x%08X:%08X - %d Cycles\n", \ (unsigned int) (((stoptime-starttime)>>32)&0xFFFFFFFF), \ (unsigned int) ((stoptime-starttime) &0xFFFFFFFF), \ (unsigned int) ((stoptime-starttime) &0xFFFFFFFF) ); } return 0; } void cleanup_module(void) { printk(KERN_DEBUG "Unloaded\n"); } Results: Test: 0x00000000:0000EA94 - 60052 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:00020977 - 133495 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:00020997 - 133527 Cycles Test: 0x00000000:0002098F - 133519 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:00020976 - 133494 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0002098A - 133514 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0002098E - 133518 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0002098A - 133514 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/