can you not use sim_cycle for this? -Jim On Tue, Apr 17, 2012 at 2:58 PM, <[email protected]> wrote: > Hello, > > I'm interesting in timing OS overhead for disk accesses. As I've discussed > with Avadh in private emails, I've extended the MARSS_DELAY_IO code in > qemu/hw/ide/core.c to support an SSD simulation. At this point, I want to > understand how much OS overhead is introduced for the operations to my > disk simulation. > > I'd like to do the following: > > * Have a C++ program that does a small file read (and make sure the file > is not cached in RAM ahead of time). > * Do rdtsc before and after the read (times A and D). > * On the hardware side, whenever I receive the disk IO command to my mods > in ptlsim.cpp, I'd like to grab the time stamp counter at the beginning > and end of the access (times B and C). > * To get the OS overhead, compute B-A and D-C. > > > My questions are: > > 1. What variable in PTLSim or QEMU should I grab that is equivalent to the > rdtsc instruction? > > 2. Just to confirm, does the rdtsc instruction work as expected in > simulation mode (i.e. it gets updated every simulated clock cycle). > > Thanks, > > Jim Stevens > > > _______________________________________________ > http://www.marss86.org > Marss86-Devel mailing list > [email protected] > https://www.cs.binghamton.edu/mailman/listinfo/marss86-devel
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