From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Oliver Oppitz" To: "Albert Cahalan" , Cc: Subject: AW: porting oprofile to ppc Date: Tue, 4 Mar 2003 17:36:15 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" In-Reply-To: <1046474835.1090.303.camel@cube> Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: I have been playing around a bit with performance counters on an MPC7441 (eMac), even found an undocumented "issue" with the "retired instructions" counter: the value is erroneously incremented by interrupts (+1 for each time entering/leaving the interrupt handler), even though it was set up for counting only user-mode instructions. I did these tests via some hijacked system call (vm86), that I adapted to read/write the SPRs. Is no good style, but works for my purposes. In any case, I would like to offer my help with the porting project. Maybe testing for a beginning, as I need to learn something about kernel modules before being of any help with that... Regards, Oliver -----Ursprüngliche Nachricht----- Von: owner-linuxppc-dev@lists.linuxppc.org [mailto:owner-linuxppc-dev@lists.linuxppc.org]Im Auftrag von Albert Cahalan Gesendet: Samstag, 1. März 2003 00:27 An: oprofile-list@lists.sourceforge.net Cc: linuxppc-dev@lists.linuxppc.org Betreff: porting oprofile to ppc I'm considering a port to the MPC7400 ("G4") PowerPC. This is out of desperation, since there isn't anything beyond gprof available for Linux/ppc users. I could use some advice. Where do I even start? Anybody else doing this or interested in helping? I run both 2.4.xx and 2.5.xx kernels, compiled from source. Neither one has any performance monitoring hooks ready to use. I could add them. What is needed? I notice that RTC support conflicts with the /dev/rtc driver. Couldn't it use the driver? Sometimes the RTC is available via memory-mapped IO, and sometimes the RTC is emulated by the /dev/rtc driver. Even on x86 you need the /dev/rtc driver to safely set the clock with SMP. I'm not a Qt fan. Can I avoid it? All my stuff is GNOME, plain X11, or non-GUI. Somehow libqt.so.2.3.1 did get installed though. On the 7xx and 74xx chips, I get a user-readable 64-bit counter that ticks at 1/16 of the memory bus clock. So on my 450 MHz Mac with a 100 MHz bus, it ticks at 6.25 MHz. There's also a privileged 32-bit count-down register that gives an interrupt. There isn't a CPU core cycle counter, unless you have a 7400 (or above?) and are willing to devote a performance counter to that purpose. The 7400 chip additionally gives me a set of performance monitoring registers, with read-only access from user code. There are four counters, PMC1 to PMC4, and control registers. I can freeze the counters in kernel mode, in user mode, and according to a flag that may be used to mark a process. There's a threshold value for some of the performance counters, taking on values from 0..63 times 2 or 32. (0,2,4,...,124,126,128,160,192,...,1952,1984,2016) So for example, I could count loads that stall for more than 1952 ticks. I can enable counters PMC2..PMC4 when PMC1 goes negative. I can freeze all the counters (or cause an interrupt) when one of PMC2...PMC4 goes negative. There are ways for external hardware to mask counting or interrupt generation. I'm not about to solder a button onto my CPU for this, but I guess it should be supported. All four counters can count: core cycles completed instructions, excluding folded branches memory cycles divided by 32, 8k, 128k, or 2M instructions dispatched (0, 1, or 2 per core cycle) Then of course each register has a selection of other choices. Of interest: instruction breakpoint matches, with a bit mask (could be abused to count system calls or interrupts) various cache things, loads, stores, etc. There must be 60 to 240 choices, depending on how one counts duplicates. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/