path: root/arch/s390/include
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authorHendrik Brueckner <brueckner@linux.ibm.com>2018-08-08 08:38:43 (GMT)
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2019-02-22 08:19:50 (GMT)
commit17bebcc68eeea3e1189f712dcba39809ad0d7a86 (patch)
treee585e5a8e45c47678415dbd0a3c19c5a8467c3bc /arch/s390/include
parent26b8317f51a20c1e4f61fbd2cc68975faad10b02 (diff)
s390/cpum_cf: Add minimal in-kernel interface for counter measurements
Introduce a minimal interface for doing counter measurements of small units of work within the kernel. Use the kernel_cpumcf_begin() function start a measurement session and, later, stop it with kernel_cpumcf_end(). During the measreument session, you can enable and start/stop counter sets by using ctr_set_* functions. To make these changes effective use the lcctl() function. You can then use the ecctr() function to extract counters from the different counter sets. Please note that you have to check whether the counter sets to be enabled are authorized. Note that when a measurement session is active, other users cannot perform counter measurements. In such cases, kernel_cpumcf_begin() indicates this with returning -EBUSY. If the counter facility is not available, kernel_cpumcf_begin() returns -ENODEV. Note that this interface is restricted to the current CPU and, thus, preemption must be turned off. Example: u32 state, err; u64 cycles, insn; err = kernel_cpumcf_begin(); if (err) goto out_busy; state = 0; ctr_set_enable(&state, CPUMF_CTR_SET_BASIC); ctr_set_start(&state, CPUMF_CTR_SET_BASIC); err = lcctl(state); if (err) goto ; /* ... do your work ... */ ctr_set_stop(&state, CPUMF_CTR_SET_BASIC); err = lcctl(state); if (err) goto out; cycles = insn = 0; ecctr(0, &cycles); ecctr(1, &insn); /* ... */ kernel_cpumcf_end(); out_busy: Signed-off-by: Hendrik Brueckner <brueckner@linux.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include')
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/s390/include/asm/cpu_mcf.h b/arch/s390/include/asm/cpu_mcf.h
index 2cd4f09..12a4224 100644
--- a/arch/s390/include/asm/cpu_mcf.h
+++ b/arch/s390/include/asm/cpu_mcf.h
@@ -63,4 +63,18 @@ int __kernel_cpumcf_begin(void);
unsigned long kernel_cpumcf_alert(int clear);
void __kernel_cpumcf_end(void);
+static inline int kernel_cpumcf_begin(void)
+ if (!cpum_cf_avail())
+ return -ENODEV;
+ preempt_disable();
+ return __kernel_cpumcf_begin();
+static inline void kernel_cpumcf_end(void)
+ __kernel_cpumcf_end();
+ preempt_enable();
#endif /* _ASM_S390_CPU_MCF_H */

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