Re: [PATCH RFC V4 4/5] kvm : pv-ticketlocks support for linux guests running on KVM hypervisor

[Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>]

On 01/16/2012 02:35 PM, Avi Kivity wrote:
> On 01/14/2012 08:26 PM, Raghavendra K T wrote:
>> Extends Linux guest running on KVM hypervisor to support pv-ticketlocks.
>>
>> During smp_boot_cpus  paravirtualied KVM guest detects if the hypervisor has
>> required feature (KVM_FEATURE_PVLOCK_KICK) to support pv-ticketlocks. If so,
>>   support for pv-ticketlocks is registered via pv_lock_ops.
>>
>> Use KVM_HC_KICK_CPU hypercall to wakeup waiting/halted vcpu.
>> +
>> +	debugfs_create_u8("zero_stats", 0644, d_spin_debug,&zero_stats);
>> +
>> +	debugfs_create_u32("taken_slow", 0444, d_spin_debug,
>> +		&spinlock_stats.contention_stats[TAKEN_SLOW]);
>> +	debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
>> +		&spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
>> +
>> +	debugfs_create_u32("released_slow", 0444, d_spin_debug,
>> +		&spinlock_stats.contention_stats[RELEASED_SLOW]);
>> +	debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
>> +		&spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
>> +
>> +	debugfs_create_u64("time_blocked", 0444, d_spin_debug,
>> +			&spinlock_stats.time_blocked);
>> +
>> +	debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
>> +		     spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
>> +
>>
>
> Please drop all of these and replace with tracepoints in the appropriate
> spots.  Everything else (including the historgram) can be reconstructed
> the tracepoints in userspace.
>

I think Jeremy pointed that tracepoints use spinlocks and hence debugfs
is the option.. no ?