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powerpc/pseries: Protect against hogging the cpu while setting up the stats 

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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2019-07-03 22:34:01 +05:30 committed by Michael Ellerman
parent d62c8deeb6
commit 18a593c8b5
3 changed files with 22 additions and 11 deletions
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2
arch/powerpc/include/asm/lppaca.h
View File

@ -201,7 +201,7 @@ 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 */

29
arch/powerpc/platforms/pseries/lpar.c
View File

@ -75,7 +75,7 @@ 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;
@ -99,6 +99,11 @@ 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;
}
}
}
@ -168,7 +173,7 @@ 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;
@ -183,6 +188,11 @@ 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
}
@ -442,7 +452,7 @@ 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;
@ -454,13 +464,13 @@ 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;
@ -472,10 +482,10 @@ 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);
}
@ -483,6 +493,7 @@ 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];
@ -517,13 +528,13 @@ 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();
}

2
arch/powerpc/platforms/pseries/setup.c
View File

@ -285,7 +285,7 @@ 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());