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authorMichael Neuling <mikey@neuling.org>2007-10-18 03:06:37 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-18 14:37:28 -0700
commit4603ac180a824197c2262747948d0179eb076e9c (patch)
tree975f9a88b95f69e1099ad22c58717b182e6416fc /arch/powerpc/kernel/time.c
parentf494f8fcb18e962839a82d542fbe6bed9cf5be07 (diff)
powerpc: add scaled time accounting
This adds POWERPC specific hooks for scaled time accounting. POWER6 includes a SPURR register. The SPURR is based off the PURR register but is scaled based on CPU frequency and issue rates. This gives a more accurate account of the instructions used per task. The PURR and timebase will be constant relative to the wall clock, irrespective of the CPU frequency. This implementation reads the SPURR register in account_system_vtime which is only call called on context witch and hard and soft irq entry and exit. The percentage of user and system time is then estimated using the ratio of these accounted by the PURR. If the SPURR is not present, the PURR read. An earlier implementation of this patch read the SPURR whenever the PURR was read, which included the system call entry and exit path. Unfortunately this showed a performance regression on lmbench runs, so was re-implemented. I've included the lmbench results here when run bare metal on POWER6. 1st column is the unpatch results. 2nd column is the results using the below patch and the 3rd is the % diff of these results from the base. 4th and 5th columns are the results and % differnce from the base using the older patch (SPURR read in syscall entry/exit path). Base Scaled-Acct SPURR-in-syscall Result Result % diff Result % diff Simple syscall: 0.3086 0.3086 0.0000 0.3452 11.8600 Simple read: 0.4591 0.4671 1.7425 0.5044 9.86713 Simple write: 0.4364 0.4366 0.0458 0.4731 8.40971 Simple stat: 2.0055 2.0295 1.1967 2.0669 3.06158 Simple fstat: 0.5962 0.5876 -1.442 0.6368 6.80979 Simple open/close: 3.1283 3.1009 -0.875 3.2088 2.57328 Select on 10 fd's: 0.8554 0.8457 -1.133 0.8667 1.32101 Select on 100 fd's: 3.5292 3.6329 2.9383 3.6664 3.88756 Select on 250 fd's: 7.9097 8.1881 3.5197 8.2242 3.97613 Select on 500 fd's: 15.2659 15.836 3.7357 15.873 3.97814 Select on 10 tcp fd's: 0.9576 0.9416 -1.670 0.9752 1.83792 Select on 100 tcp fd's: 7.248 7.2254 -0.311 7.2685 0.28283 Select on 250 tcp fd's: 17.7742 17.707 -0.375 17.749 -0.1406 Select on 500 tcp fd's: 35.4258 35.25 -0.496 35.286 -0.3929 Signal handler installation: 0.6131 0.6075 -0.913 0.647 5.52927 Signal handler overhead: 2.0919 2.1078 0.7600 2.1831 4.35967 Protection fault: 0.7345 0.7478 1.8107 0.8031 9.33968 Pipe latency: 33.006 16.398 -50.31 33.475 1.42368 AF_UNIX sock stream latency: 14.5093 30.910 113.03 30.715 111.692 Process fork+exit: 219.8 222.8 1.3648 229.37 4.35623 Process fork+execve: 876.14 873.28 -0.32 868.66 -0.8533 Process fork+/bin/sh -c: 2830 2876.5 1.6431 2958 4.52296 File /var/tmp/XXX write bw: 1193497 1195536 0.1708 118657 -0.5799 Pagefaults on /var/tmp/XXX: 3.1272 3.2117 2.7020 3.2521 3.99398 Also, kernel compile times show no difference with this patch applied. [pbadari@us.ibm.com: Avoid unnecessary PURR reading] Signed-off-by: Michael Neuling <mikey@neuling.org> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Jay Lan <jlan@engr.sgi.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/powerpc/kernel/time.c')
-rw-r--r--arch/powerpc/kernel/time.c32
1 files changed, 30 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 863a5d6d9b18..9eb3284deac4 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -212,23 +212,44 @@ static u64 read_purr(void)
}
/*
+ * Read the SPURR on systems that have it, otherwise the purr
+ */
+static u64 read_spurr(u64 purr)
+{
+ if (cpu_has_feature(CPU_FTR_SPURR))
+ return mfspr(SPRN_SPURR);
+ return purr;
+}
+
+/*
* Account time for a transition between system, hard irq
* or soft irq state.
*/
void account_system_vtime(struct task_struct *tsk)
{
- u64 now, delta;
+ u64 now, nowscaled, delta, deltascaled;
unsigned long flags;
local_irq_save(flags);
now = read_purr();
delta = now - get_paca()->startpurr;
get_paca()->startpurr = now;
+ nowscaled = read_spurr(now);
+ deltascaled = nowscaled - get_paca()->startspurr;
+ get_paca()->startspurr = nowscaled;
if (!in_interrupt()) {
+ /* deltascaled includes both user and system time.
+ * Hence scale it based on the purr ratio to estimate
+ * the system time */
+ deltascaled = deltascaled * get_paca()->system_time /
+ (get_paca()->system_time + get_paca()->user_time);
delta += get_paca()->system_time;
get_paca()->system_time = 0;
}
account_system_time(tsk, 0, delta);
+ get_paca()->purrdelta = delta;
+ account_system_time_scaled(tsk, deltascaled);
+ get_paca()->spurrdelta = deltascaled;
local_irq_restore(flags);
}
@@ -240,11 +261,17 @@ void account_system_vtime(struct task_struct *tsk)
*/
void account_process_vtime(struct task_struct *tsk)
{
- cputime_t utime;
+ cputime_t utime, utimescaled;
utime = get_paca()->user_time;
get_paca()->user_time = 0;
account_user_time(tsk, utime);
+
+ /* Estimate the scaled utime by scaling the real utime based
+ * on the last spurr to purr ratio */
+ utimescaled = utime * get_paca()->spurrdelta / get_paca()->purrdelta;
+ get_paca()->spurrdelta = get_paca()->purrdelta = 0;
+ account_user_time_scaled(tsk, utimescaled);
}
static void account_process_time(struct pt_regs *regs)
@@ -266,6 +293,7 @@ struct cpu_purr_data {
int initialized; /* thread is running */
u64 tb; /* last TB value read */
u64 purr; /* last PURR value read */
+ u64 spurr; /* last SPURR value read */
};
/*