Messages in this thread | | | From | Vince Weaver <> | Date | Mon, 2 Mar 2015 17:23:35 -0500 (EST) | Subject | Re: [patch] perf_event_open.2: 3.19 PERF_SAMPLE_REGS_INTR support |
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On Mon, 2 Mar 2015, Stephane Eranian wrote:
> Vince, REGS_USER is user ONLY. It does not capture machine state if PMU > interrupt occurred inside the kernel. REGS_USER is useful in support of dwarf > based user level call stack unwinding. Otherwise REGS_INTR is what most > analysis tools need.
so the summary is:
REGS_USER : gives you the registers at the time of interrupt, but always in user mode (if in kernel reports last ip before entered kernel) useful for stack unwinding
REGS_INTR and precise_ip=0: same as REGS_USER
REGS_INTR and precise_ip>0 and PEBS hardware: gives you the register state at time of interrupt. Can be inside of kernel.
do not enable REGS_USER and REG_INTR at the same time as REGS_USER will have REG_INTR values and cannot be used for user stack unwinding
Vince
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