diff mbox series

[v3,8/9] powerpc/pseries: Protect against hogging the cpu while setting up the stats

Message ID 3d91bc5ea948b388bbc1886c7b739e55e020c8cf.1562171646.git.naveen.n.rao@linux.vnet.ibm.com (mailing list archive)
State Accepted
Commit 18a593c8b5426f6a08bcb353636d761a83f78d9e
Headers show
Series Provide vcpu dispatch statistics | expand

Checks

Context Check Description
snowpatch_ozlabs/apply_patch success Successfully applied on branch next (f531d5e8f55b3767217b5d1be0ce1f1acd10167c)
snowpatch_ozlabs/checkpatch warning total: 0 errors, 0 warnings, 1 checks, 111 lines checked

Commit Message

Naveen N. Rao July 3, 2019, 5:04 p.m. UTC
When enabling or disabling the vcpu dispatch statistics, we do a lot of
work including allocating/deallocating memory across all possible cpus
for the DTL buffer. In order to guard against hogging the cpu for too
long, track the time we're taking and yield the processor if necessary.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/lppaca.h      |  2 +-
 arch/powerpc/platforms/pseries/lpar.c  | 29 ++++++++++++++++++--------
 arch/powerpc/platforms/pseries/setup.c |  2 +-
 3 files changed, 22 insertions(+), 11 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h
index f60257c9766d..3b4b305796ae 100644
--- a/arch/powerpc/include/asm/lppaca.h
+++ b/arch/powerpc/include/asm/lppaca.h
@@ -188,7 +188,7 @@  extern rwlock_t dtl_access_lock;
 extern void (*dtl_consumer)(struct dtl_entry *entry, u64 index);
 
 extern void register_dtl_buffer(int cpu);
-extern void alloc_dtl_buffers(void);
+extern void alloc_dtl_buffers(unsigned long *time_limit);
 extern long hcall_vphn(unsigned long cpu, u64 flags, __be32 *associativity);
 
 #endif /* CONFIG_PPC_BOOK3S */
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 951a3d755190..4bee9b4fc876 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -62,7 +62,7 @@  static u8 dtl_mask = DTL_LOG_PREEMPT;
 static u8 dtl_mask;
 #endif
 
-void alloc_dtl_buffers(void)
+void alloc_dtl_buffers(unsigned long *time_limit)
 {
 	int cpu;
 	struct paca_struct *pp;
@@ -86,6 +86,11 @@  void alloc_dtl_buffers(void)
 		pp->dispatch_log = dtl;
 		pp->dispatch_log_end = dtl + N_DISPATCH_LOG;
 		pp->dtl_curr = dtl;
+
+		if (time_limit && time_after(jiffies, *time_limit)) {
+			cond_resched();
+			*time_limit = jiffies + HZ;
+		}
 	}
 }
 
@@ -154,7 +159,7 @@  static int vcpudispatch_stats_freq = 50;
 static __be32 *vcpu_associativity, *pcpu_associativity;
 
 
-static void free_dtl_buffers(void)
+static void free_dtl_buffers(unsigned long *time_limit)
 {
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
 	int cpu;
@@ -169,6 +174,11 @@  static void free_dtl_buffers(void)
 		pp->dispatch_log = 0;
 		pp->dispatch_log_end = 0;
 		pp->dtl_curr = 0;
+
+		if (time_limit && time_after(jiffies, *time_limit)) {
+			cond_resched();
+			*time_limit = jiffies + HZ;
+		}
 	}
 #endif
 }
@@ -428,7 +438,7 @@  static void reset_global_dtl_mask(void)
 		lppaca_of(cpu).dtl_enable_mask = dtl_mask;
 }
 
-static int dtl_worker_enable(void)
+static int dtl_worker_enable(unsigned long *time_limit)
 {
 	int rc = 0, state;
 
@@ -440,13 +450,13 @@  static int dtl_worker_enable(void)
 	set_global_dtl_mask(DTL_LOG_ALL);
 
 	/* Setup dtl buffers and register those */
-	alloc_dtl_buffers();
+	alloc_dtl_buffers(time_limit);
 
 	state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/dtl:online",
 					dtl_worker_online, dtl_worker_offline);
 	if (state < 0) {
 		pr_err("vcpudispatch_stats: unable to setup workqueue for DTL processing\n");
-		free_dtl_buffers();
+		free_dtl_buffers(time_limit);
 		reset_global_dtl_mask();
 		write_unlock(&dtl_access_lock);
 		rc = -EINVAL;
@@ -458,10 +468,10 @@  static int dtl_worker_enable(void)
 	return rc;
 }
 
-static void dtl_worker_disable(void)
+static void dtl_worker_disable(unsigned long *time_limit)
 {
 	cpuhp_remove_state(dtl_worker_state);
-	free_dtl_buffers();
+	free_dtl_buffers(time_limit);
 	reset_global_dtl_mask();
 	write_unlock(&dtl_access_lock);
 }
@@ -469,6 +479,7 @@  static void dtl_worker_disable(void)
 static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,
 		size_t count, loff_t *ppos)
 {
+	unsigned long time_limit = jiffies + HZ;
 	struct vcpu_dispatch_data *disp;
 	int rc, cmd, cpu;
 	char buf[16];
@@ -503,13 +514,13 @@  static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,
 			disp->last_disp_cpu = -1;
 		}
 
-		rc = dtl_worker_enable();
+		rc = dtl_worker_enable(&time_limit);
 		if (rc) {
 			destroy_cpu_associativity();
 			goto out;
 		}
 	} else {
-		dtl_worker_disable();
+		dtl_worker_disable(&time_limit);
 		destroy_cpu_associativity();
 	}
 
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index e4d75b958593..76fd6de90581 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -279,7 +279,7 @@  static int alloc_dispatch_logs(void)
 	if (!dtl_cache)
 		return 0;
 
-	alloc_dtl_buffers();
+	alloc_dtl_buffers(0);
 
 	/* Register the DTL for the current (boot) cpu */
 	register_dtl_buffer(smp_processor_id());