Nest/core pmu units are enabled only when it is used. A reference count is
maintained for the events which uses the nest/core pmu units. Currently in
*_imc_counters_release function a WARN() is used for notification of any
underflow of ref count.
The case where event ref count hit a negative value is, when perf session is
started, followed by offlining of all cpus in a given core.
i.e. in cpuhotplug offline path ppc_core_imc_cpu_offline() function set the
ref->count to zero, if the current cpu which is about to offline is the last
cpu in a given core and make an OPAL call to disable the engine in that core.
And on perf session termination, perf->destroy (core_imc_counters_release) will
first decrement the ref->count for this core and based on the ref->count value
an opal call is made to disable the core-imc engine.
Now, since cpuhotplug path already clears the ref->count for core and disabled
the engine, perf->destroy() decrementing again at event termination make it
negative which in turn fires the WARN_ON. The same happens for nest units.
Add a check to see if the reference count is alreday zero, before decrementing
the count, so that the ref count will not hit a negative value.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Reviewed-by: Santosh Sivaraj <santosh@fossix.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
nest_imc_refc is a reference count struct, used to track number of
active perf sessions using the nest units.
Currently the code accesses nest_imc_refc using node_id, which is
incorrect, the array is indexed by node number. Meaning in the case of
sparse node ids we index off the end of the array.
Fix it to use get_nest_pmu_ref() which uses the existing per-cpu
variable local_nest_imc_refc.
Fixes: 885dcd709b ('powerpc/perf: Add nest IMC PMU support')
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
[mpe: Tweak change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
In a multi node system with discontiguous node ids, nest event values
are not showing up properly. eg. lscpu output:
NUMA node0 CPU(s): 0-15
NUMA node8 CPU(s): 16-31
Nest event values on such systems can be counted on CPUs <= 15:
$./perf stat -e 'nest_powerbus0_imc/PM_PB_CYC/' -C 0-14 -I 1000 sleep 1000
# time counts unit events
1.000294577 30,17,24,42,880 nest_powerbus0_imc/PM_PB_CYC/
But not on CPUs >= 16:
$./perf stat -e 'nest_powerbus0_imc/PM_PB_CYC/' -C 16-28 -I 1000 sleep 1000
# time counts unit events
1.000049902 <not supported> nest_powerbus0_imc/PM_PB_CYC/
This is because, when fetching the reference count, the node id (which
may be sparse) is used as the array index, not the node number (which
is 0 based and contiguous).
Fix it by using the node number as the array index.
$./perf stat -e 'nest_powerbus0_imc/PM_PB_CYC/' -C 16-28 -I 1000 sleep 1000
# time counts unit events
1.000241961 26,12,35,28,704 nest_powerbus0_imc/PM_PB_CYC/
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
[mpe: Change log tweaks for clarity and brevity]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This function is not called with the nest_init_lock held, and it also
unlocks the nest_init_lock immediately below, so it's fairly clear
that this is a typo and should be locking the lock.
Fixes: 885dcd709b ("powerpc/perf: Add nest IMC PMU support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Add support to register Thread In-Memory Collection PMU counters.
Patch adds thread IMC specific data structures, along with memory
init functions and CPU hotplug support.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Add support to register Core In-Memory Collection PMU counters.
Patch adds core IMC specific data structures, along with memory
init functions and CPU hotplug support.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Add support to register Nest In-Memory Collection PMU counters.
Patch adds a new device file called "imc-pmu.c" under powerpc/perf
folder to contain all the device PMU functions.
Device tree parser code added to parse the PMU events information
and create sysfs event attributes for the PMU.
Cpumask attribute added along with Cpu hotplug online/offline functions
specific for nest PMU. A new state "CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE"
added for the cpu hotplug callbacks. Error handle path frees the memory
and unregisters the CPU hotplug callbacks.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
