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This patch has been reworked since RFC version. In the RFC, this patch was preceded by a patch clearing MSR RI for all PPC32 at all time at exception prologs. Now MSR RI clearing is done only when this 8xx perf events functionality is compiled in, it is therefore limited to 8xx and merged inside this patch. Other main changes have been to take into account detailed review from Peter Zijlstra. The instructions counter has been reworked to behave as a free running counter like the three other counters. The 8xx has no PMU, however some events can be emulated by other means. This patch implements the following events (as reported by 'perf list'): cpu-cycles OR cycles [Hardware event] instructions [Hardware event] dTLB-load-misses [Hardware cache event] iTLB-load-misses [Hardware cache event] 'cycles' event is implemented using the timebase clock. Timebase clock corresponds to CPU clock divided by 16, so number of cycles is approximatly 16 times the number of TB ticks On the 8xx, TLB misses are handled by software. It is therefore easy to count all TLB misses each time the TLB miss exception is called. 'instructions' is calculated by using instruction watchpoint counter. This patch sets counter A to count instructions at address greater than 0, hence we count all instructions executed while MSR RI bit is set. The counter is set to the maximum which is 0xffff. Every 65535 instructions, debug instruction breakpoint exception fires. The exception handler increments a counter in memory which then represent the upper part of the instruction counter. We therefore end up with a 48 bits counter. In order to avoid unnecessary overhead while no perf event is active, this counter is started when the first event referring to this counter is added, and the counter is stopped when the last event referring to it is deleted. In order to properly support breakpoint exceptions, MSR RI bit has to be unset in exception epilogs in order to avoid breakpoint exceptions during critical sections during changes to SRR0 and SRR1 would be problematic. All counters are handled as free running counters. Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: Scott Wood <oss@buserror.net> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.