* [PATCH] 2.5.39 s390 (16/26): timer interrupts.
@ 2002-09-30 12:59 Martin Schwidefsky
0 siblings, 0 replies; only message in thread
From: Martin Schwidefsky @ 2002-09-30 12:59 UTC (permalink / raw)
To: linux-kernel, torvalds
Make timer interrupt independent from boot cpu and do several ticks in one
go if a virtual cpu didn't get an interrupt for a period of time > HZ.
diff -urN linux-2.5.39/arch/s390/kernel/setup.c linux-2.5.39-s390/arch/s390/kernel/setup.c
--- linux-2.5.39/arch/s390/kernel/setup.c Mon Sep 30 13:25:21 2002
+++ linux-2.5.39-s390/arch/s390/kernel/setup.c Mon Sep 30 13:32:53 2002
@@ -52,7 +52,6 @@
struct { unsigned long addr, size, type; } memory_chunk[16] = { { 0 } };
#define CHUNK_READ_WRITE 0
#define CHUNK_READ_ONLY 1
-__u16 boot_cpu_addr;
int cpus_initialized = 0;
unsigned long cpu_initialized = 0;
volatile int __cpu_logical_map[NR_CPUS]; /* logical cpu to cpu address */
@@ -474,8 +473,7 @@
lowcore->jiffy_timer = -1LL;
set_prefix((__u32) lowcore);
cpu_init();
- boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
- __cpu_logical_map[0] = boot_cpu_addr;
+ __cpu_logical_map[0] = S390_lowcore.cpu_data.cpu_addr;
/*
* Create kernel page tables and switch to virtual addressing.
diff -urN linux-2.5.39/arch/s390/kernel/smp.c linux-2.5.39-s390/arch/s390/kernel/smp.c
--- linux-2.5.39/arch/s390/kernel/smp.c Mon Sep 30 13:25:21 2002
+++ linux-2.5.39-s390/arch/s390/kernel/smp.c Mon Sep 30 13:32:53 2002
@@ -41,7 +41,6 @@
/* prototypes */
extern int cpu_idle(void * unused);
-extern __u16 boot_cpu_addr;
extern volatile int __cpu_logical_map[];
/*
@@ -426,6 +425,7 @@
void __init smp_check_cpus(unsigned int max_cpus)
{
int curr_cpu, num_cpus;
+ __u16 boot_cpu_addr;
boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
current_thread_info()->cpu = 0;
diff -urN linux-2.5.39/arch/s390/kernel/time.c linux-2.5.39-s390/arch/s390/kernel/time.c
--- linux-2.5.39/arch/s390/kernel/time.c Mon Sep 30 13:25:21 2002
+++ linux-2.5.39-s390/arch/s390/kernel/time.c Mon Sep 30 13:32:53 2002
@@ -38,11 +38,18 @@
#define USECS_PER_JIFFY ((unsigned long) 1000000/HZ)
#define CLK_TICKS_PER_JIFFY ((unsigned long) USECS_PER_JIFFY << 12)
+/*
+ * Create a small time difference between the timer interrupts
+ * on the different cpus to avoid lock contention.
+ */
+#define CPU_DEVIATION (smp_processor_id() << 12)
+
#define TICK_SIZE tick
u64 jiffies_64;
static ext_int_info_t ext_int_info_timer;
+static uint64_t xtime_cc;
static uint64_t init_timer_cc;
extern rwlock_t xtime_lock;
@@ -118,58 +125,90 @@
write_unlock_irq(&xtime_lock);
}
+static inline __u32 div64_32(__u64 dividend, __u32 divisor)
+{
+ register_pair rp;
+
+ rp.pair = dividend;
+ asm ("dr %0,%1" : "+d" (rp) : "d" (divisor));
+ return rp.subreg.odd;
+}
+
/*
* timer_interrupt() needs to keep up the real-time clock,
* as well as call the "do_timer()" routine every clocktick
*/
-
-#ifdef CONFIG_SMP
-extern __u16 boot_cpu_addr;
-#endif
-
static void do_comparator_interrupt(struct pt_regs *regs, __u16 error_code)
{
int cpu = smp_processor_id();
+ __u64 tmp;
+ __u32 ticks;
+
+ /* Calculate how many ticks have passed. */
+ asm volatile ("STCK 0(%0)" : : "a" (&tmp) : "memory", "cc");
+ tmp = tmp - S390_lowcore.jiffy_timer;
+ if (tmp >= 2*CLK_TICKS_PER_JIFFY) { /* more than one tick ? */
+ ticks = div64_32(tmp >> 1, CLK_TICKS_PER_JIFFY >> 1);
+ S390_lowcore.jiffy_timer +=
+ CLK_TICKS_PER_JIFFY * (__u64) ticks;
+ } else {
+ ticks = 1;
+ S390_lowcore.jiffy_timer += CLK_TICKS_PER_JIFFY;
+ }
+
+ /* set clock comparator for next tick */
+ tmp = S390_lowcore.jiffy_timer + CLK_TICKS_PER_JIFFY + CPU_DEVIATION;
+ asm volatile ("SCKC %0" : : "m" (tmp));
irq_enter();
+#ifdef CONFIG_SMP
/*
- * set clock comparator for next tick
+ * Do not rely on the boot cpu to do the calls to do_timer.
+ * Spread it over all cpus instead.
*/
- S390_lowcore.jiffy_timer += CLK_TICKS_PER_JIFFY;
- asm volatile ("SCKC %0" : : "m" (S390_lowcore.jiffy_timer));
-
-#ifdef CONFIG_SMP
- if (S390_lowcore.cpu_data.cpu_addr == boot_cpu_addr)
- write_lock(&xtime_lock);
-
- update_process_times(user_mode(regs));
-
- if (S390_lowcore.cpu_data.cpu_addr == boot_cpu_addr) {
- do_timer(regs);
- write_unlock(&xtime_lock);
+ write_lock(&xtime_lock);
+ if (S390_lowcore.jiffy_timer > xtime_cc) {
+ __u32 xticks;
+
+ tmp = S390_lowcore.jiffy_timer - xtime_cc;
+ if (tmp >= 2*CLK_TICKS_PER_JIFFY) {
+ xticks = div64_32(tmp >> 1, CLK_TICKS_PER_JIFFY >> 1);
+ xtime_cc += (__u64) xticks * CLK_TICKS_PER_JIFFY;
+ } else {
+ xticks = 1;
+ xtime_cc += CLK_TICKS_PER_JIFFY;
+ }
+ while (xticks--)
+ do_timer(regs);
}
+ write_unlock(&xtime_lock);
+ while (ticks--)
+ update_process_times(user_mode(regs));
#else
- do_timer(regs);
+ while (ticks--)
+ do_timer(regs);
#endif
irq_exit();
}
/*
- * Start the clock comparator on the current CPU
+ * Start the clock comparator on the current CPU.
*/
void init_cpu_timer(void)
{
unsigned long cr0;
+ __u64 timer;
/* allow clock comparator timer interrupt */
asm volatile ("STCTL 0,0,%0" : "=m" (cr0) : : "memory");
cr0 |= 0x800;
asm volatile ("LCTL 0,0,%0" : : "m" (cr0) : "memory");
- S390_lowcore.jiffy_timer = (__u64) jiffies * CLK_TICKS_PER_JIFFY;
- S390_lowcore.jiffy_timer += init_timer_cc + CLK_TICKS_PER_JIFFY;
- asm volatile ("SCKC %0" : : "m" (S390_lowcore.jiffy_timer));
+ timer = init_timer_cc + jiffies_64 * CLK_TICKS_PER_JIFFY;
+ S390_lowcore.jiffy_timer = timer;
+ timer += CLK_TICKS_PER_JIFFY + CPU_DEVIATION;
+ asm volatile ("SCKC %0" : : "m" (timer));
}
/*
@@ -178,7 +217,7 @@
*/
void __init time_init(void)
{
- __u64 set_time_cc;
+ __u64 set_time_cc;
int cc;
/* kick the TOD clock */
@@ -201,8 +240,9 @@
}
/* set xtime */
- set_time_cc = init_timer_cc - 0x8126d60e46000000LL +
- (0x3c26700LL*1000000*4096);
+ xtime_cc = init_timer_cc;
+ set_time_cc = init_timer_cc - 0x8126d60e46000000LL +
+ (0x3c26700LL*1000000*4096);
tod_to_timeval(set_time_cc, &xtime);
/* request the 0x1004 external interrupt */
diff -urN linux-2.5.39/arch/s390x/kernel/setup.c linux-2.5.39-s390/arch/s390x/kernel/setup.c
--- linux-2.5.39/arch/s390x/kernel/setup.c Mon Sep 30 13:25:21 2002
+++ linux-2.5.39-s390/arch/s390x/kernel/setup.c Mon Sep 30 13:32:53 2002
@@ -52,7 +52,6 @@
struct { unsigned long addr, size, type; } memory_chunk[16] = { { 0 } };
#define CHUNK_READ_WRITE 0
#define CHUNK_READ_ONLY 1
-__u16 boot_cpu_addr;
int cpus_initialized = 0;
unsigned long cpu_initialized = 0;
volatile int __cpu_logical_map[NR_CPUS]; /* logical cpu to cpu address */
@@ -464,8 +463,7 @@
lowcore->jiffy_timer = -1LL;
set_prefix((__u32)(__u64) lowcore);
cpu_init();
- boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
- __cpu_logical_map[0] = boot_cpu_addr;
+ __cpu_logical_map[0] = S390_lowcore.cpu_data.cpu_addr;
/*
* Create kernel page tables and switch to virtual addressing.
diff -urN linux-2.5.39/arch/s390x/kernel/smp.c linux-2.5.39-s390/arch/s390x/kernel/smp.c
--- linux-2.5.39/arch/s390x/kernel/smp.c Mon Sep 30 13:25:21 2002
+++ linux-2.5.39-s390/arch/s390x/kernel/smp.c Mon Sep 30 13:32:53 2002
@@ -40,7 +40,6 @@
/* prototypes */
extern int cpu_idle(void * unused);
-extern __u16 boot_cpu_addr;
extern volatile int __cpu_logical_map[];
/*
@@ -407,6 +406,7 @@
void __init smp_check_cpus(unsigned int max_cpus)
{
int curr_cpu, num_cpus;
+ __u16 boot_cpu_addr;
boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
current_thread_info()->cpu = 0;
diff -urN linux-2.5.39/arch/s390x/kernel/time.c linux-2.5.39-s390/arch/s390x/kernel/time.c
--- linux-2.5.39/arch/s390x/kernel/time.c Mon Sep 30 13:25:21 2002
+++ linux-2.5.39-s390/arch/s390x/kernel/time.c Mon Sep 30 13:32:53 2002
@@ -37,11 +37,18 @@
#define USECS_PER_JIFFY ((unsigned long) 1000000/HZ)
#define CLK_TICKS_PER_JIFFY ((unsigned long) USECS_PER_JIFFY << 12)
+/*
+ * Create a small time difference between the timer interrupts
+ * on the different cpus to avoid lock contention.
+ */
+#define CPU_DEVIATION (smp_processor_id() << 12)
+
#define TICK_SIZE tick
u64 jiffies_64;
static ext_int_info_t ext_int_info_timer;
+static uint64_t xtime_cc;
static uint64_t init_timer_cc;
extern rwlock_t xtime_lock;
@@ -117,54 +124,77 @@
* timer_interrupt() needs to keep up the real-time clock,
* as well as call the "do_timer()" routine every clocktick
*/
-
-#ifdef CONFIG_SMP
-extern __u16 boot_cpu_addr;
-#endif
-
static void do_comparator_interrupt(struct pt_regs *regs, __u16 error_code)
{
int cpu = smp_processor_id();
+ __u64 tmp;
+ __u32 ticks;
+
+ /* Calculate how many ticks have passed. */
+ asm volatile ("STCK 0(%0)" : : "a" (&tmp) : "memory", "cc");
+ tmp = tmp - S390_lowcore.jiffy_timer;
+ if (tmp >= 2*CLK_TICKS_PER_JIFFY) { /* more than one tick ? */
+ ticks = tmp / CLK_TICKS_PER_JIFFY;
+ S390_lowcore.jiffy_timer +=
+ CLK_TICKS_PER_JIFFY * (__u64) ticks;
+ } else {
+ ticks = 1;
+ S390_lowcore.jiffy_timer += CLK_TICKS_PER_JIFFY;
+ }
+
+ /* set clock comparator for next tick */
+ tmp = S390_lowcore.jiffy_timer + CLK_TICKS_PER_JIFFY + CPU_DEVIATION;
+ asm volatile ("SCKC %0" : : "m" (tmp));
irq_enter();
+#ifdef CONFIG_SMP
/*
- * set clock comparator for next tick
+ * Do not rely on the boot cpu to do the calls to do_timer.
+ * Spread it over all cpus instead.
*/
- S390_lowcore.jiffy_timer += CLK_TICKS_PER_JIFFY;
- asm volatile ("SCKC %0" : : "m" (S390_lowcore.jiffy_timer));
-
-#ifdef CONFIG_SMP
- if (S390_lowcore.cpu_data.cpu_addr == boot_cpu_addr)
- write_lock(&xtime_lock);
-
- update_process_times(user_mode(regs));
-
- if (S390_lowcore.cpu_data.cpu_addr == boot_cpu_addr) {
- do_timer(regs);
- write_unlock(&xtime_lock);
+ write_lock(&xtime_lock);
+ if (S390_lowcore.jiffy_timer > xtime_cc) {
+ __u32 xticks;
+
+ tmp = S390_lowcore.jiffy_timer - xtime_cc;
+ if (tmp >= 2*CLK_TICKS_PER_JIFFY) {
+ xticks = tmp / CLK_TICKS_PER_JIFFY;
+ xtime_cc += (__u64) xticks * CLK_TICKS_PER_JIFFY;
+ } else {
+ xticks = 1;
+ xtime_cc += CLK_TICKS_PER_JIFFY;
+ }
+ while (xticks--)
+ do_timer(regs);
}
+ write_unlock(&xtime_lock);
+ while (ticks--)
+ update_process_times(user_mode(regs));
#else
- do_timer(regs);
+ while (ticks--)
+ do_timer(regs);
#endif
irq_exit();
}
/*
- * Start the clock comparator on the current CPU
+ * Start the clock comparator on the current CPU.
*/
void init_cpu_timer(void)
{
unsigned long cr0;
+ __u64 timer;
/* allow clock comparator timer interrupt */
asm volatile ("STCTG 0,0,%0" : "=m" (cr0) : : "memory");
cr0 |= 0x800;
asm volatile ("LCTLG 0,0,%0" : : "m" (cr0) : "memory");
- S390_lowcore.jiffy_timer = (__u64) jiffies * CLK_TICKS_PER_JIFFY;
- S390_lowcore.jiffy_timer += init_timer_cc + CLK_TICKS_PER_JIFFY;
- asm volatile ("SCKC %0" : : "m" (S390_lowcore.jiffy_timer));
+ timer = init_timer_cc + jiffies_64 * CLK_TICKS_PER_JIFFY;
+ S390_lowcore.jiffy_timer = timer;
+ timer += CLK_TICKS_PER_JIFFY + CPU_DEVIATION;
+ asm volatile ("SCKC %0" : : "m" (timer));
}
/*
@@ -173,7 +203,7 @@
*/
void __init time_init(void)
{
- __u64 set_time_cc;
+ __u64 set_time_cc;
int cc;
/* kick the TOD clock */
@@ -196,8 +226,9 @@
}
/* set xtime */
- set_time_cc = init_timer_cc - 0x8126d60e46000000LL +
- (0x3c26700LL*1000000*4096);
+ xtime_cc = init_timer_cc;
+ set_time_cc = init_timer_cc - 0x8126d60e46000000LL +
+ (0x3c26700LL*1000000*4096);
tod_to_timeval(set_time_cc, &xtime);
/* request the 0x1004 external interrupt */
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2002-09-30 12:59 [PATCH] 2.5.39 s390 (16/26): timer interrupts Martin Schwidefsky
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