Artyom Tarasenko writes: [...] > QEMU 1.0.50 monitor - type 'help' for more information > (qemu) profile > unknown command: 'profile' > (qemu) info profile > async time 38505498320 (38.505) > qemu time 35947093161 (35.947)
> Is there a way to find out more? Command "info jit" also has some information added when compiled with profiling support. Search for CONFIG_PROFILER to see which code is activated during profiling. > Next I tried gprof: > build-prof $ gprof sparc64-softmmu/qemu-system-sparc64 gmon.out > Flat profile: > Each sample counts as 0.01 seconds. > % cumulative self self total > time seconds seconds calls Ts/call Ts/call name > 100.00 5.06 5.06 main > Hmm. Not very informative. Is there a way to find out more details? Did you run QEMU for a reasonable amount of time? gprof uses sampling to capture its execution time statistics, so a small execution of QEMU will not be able to capture any meaningful information. [...] > Here it looks like "compute_all_sub" and "compute_all_sub_xcc" are > good candidates for optimizing: together they take the same amount of > time as cpu_sparc_exec. I guess both operations would be trivial in > the x86_64 assembler. What would be the best strategy to make TCG take > the advantage of running on a x86_64 host? A quick look into the code reveals that these two are called from a TCG helper (helper_compute_psr), so I see two approaches here applicable to the most frequently used "sub-operations" in helper_compute_psr: * Define new simpler helpers for those sub-operations that can be declared with TCG_CALL_CONST and generate the new psr/xcc values in temporal registers. You must make sure any other code will still be able to use the new psr/xcc values. * Reimplement these sub-operations in pure TCG code. But first, make sure you run a proper benchmark to establish where are the hotspots in the sparc code for QEMU. The problem here is to establish what a proper benchmark is :) Lluis -- "And it's much the same thing with knowledge, for whenever you learn something new, the whole world becomes that much richer." -- The Princess of Pure Reason, as told by Norton Juster in The Phantom Tollbooth