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Knowing how long we spend in firmware calls is an important part of
minimising OS jitter.
This patch adds tracepoints to each OPAL call. If tracepoints are
enabled we branch out to a common routine that calls an entry and exit
tracepoint.
This allows us to write tools that monitor the frequency and duration
of OPAL calls, eg:
name count total(ms) min(ms) max(ms) avg(ms) period(ms)
OPAL_HANDLE_INTERRUPT 5 0.199 0.037 0.042 0.040 12547.545
OPAL_POLL_EVENTS 204 2.590 0.012 0.036 0.013 2264.899
OPAL_PCI_MSI_EOI 2830 3.066 0.001 0.005 0.001 81.166
We use jump labels if configured, which means we only add a single
nop instruction to every OPAL call when the tracepoints are disabled.
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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irq_entry, irq_exit, timer_interrupt_entry and timer_interrupt_exit
all do the same thing so use DECLARE_EVENT_CLASS to avoid duplicating
everything 4 times.
This saves quite a lot of space in both instruction text and data:
text data bss dec hex filename
9265 19622 16 28903 70e7 arch/powerpc/kernel/irq.o
6817 19019 16 25852 64fc arch/powerpc/kernel/irq.o
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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While most users of the hcall tracepoints will only want the opcode
and return code, some will want all the arguments. To avoid the
complexity of using varargs we pass a pointer to the register save
area, which contains all the arguments.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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Add hcall_entry and hcall_exit tracepoints. This replaces the inline
assembly HCALL_STATS code and converts it to use the new tracepoints.
To keep the disabled case as quick as possible, we embed a status word
in the TOC so we can get at it with a single load. By doing so we
keep the overhead at a minimum. Time taken for a null hcall:
No tracepoint code: 135.79 cycles
Disabled tracepoints: 137.95 cycles
For reference, before this patch enabling HCALL_STATS resulted in a null
hcall of 201.44 cycles!
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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We can monitor the effectiveness of our power management of both the
kernel and hypervisor by probing the timer interrupt. For example, on
this box we see 10.37s timer interrupts on an idle core:
<idle>-0 [010] 3900.671297: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
<idle>-0 [010] 3900.671302: timer_interrupt_exit: pt_regs=c0000000ce1e7b10
<idle>-0 [010] 3911.042963: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
<idle>-0 [010] 3911.042968: timer_interrupt_exit: pt_regs=c0000000ce1e7b10
<idle>-0 [010] 3921.414630: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
<idle>-0 [010] 3921.414635: timer_interrupt_exit: pt_regs=c0000000ce1e7b10
Since we have a 207MHz decrementer it will go negative and fire every 10.37s
even if Linux is completely idle.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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This adds powerpc-specific tracepoints for interrupt entry and exit.
While we already have generic irq_handler_entry and irq_handler_exit
tracepoints there are cases on our virtualised powerpc machines where an
interrupt is presented to the OS, but subsequently handled by the hypervisor.
This means no OS interrupt handler is invoked.
Here is an example on a POWER6 machine with the patch below applied:
<idle>-0 [006] 3243.949840744: irq_entry: pt_regs=c0000000ce31fb10
<idle>-0 [006] 3243.949850520: irq_exit: pt_regs=c0000000ce31fb10
<idle>-0 [007] 3243.950218208: irq_entry: pt_regs=c0000000ce323b10
<idle>-0 [007] 3243.950224080: irq_exit: pt_regs=c0000000ce323b10
<idle>-0 [000] 3244.021879320: irq_entry: pt_regs=c000000000a63aa0
<idle>-0 [000] 3244.021883616: irq_handler_entry: irq=87 handler=eth0
<idle>-0 [000] 3244.021887328: irq_handler_exit: irq=87 return=handled
<idle>-0 [000] 3244.021897408: irq_exit: pt_regs=c000000000a63aa0
Here we see two phantom interrupts (no handler was invoked), followed
by a real interrupt for eth0. Without the tracepoints in this patch we
would have missed the phantom interrupts.
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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