Kirill Batuzov <batuz...@ispras.ru> writes: > On Thu, 27 Mar 2014, alex.ben...@linaro.org wrote: > >> From: Alex Bennée <alex.ben...@linaro.org> >> >> This allows the perf tool to map samples to each individual translation >> block. This could be expanded for user space but currently it gives >> enough information to find any hotblocks by other means. > > I'm in favor of this patch. Being able to profile guest code with perf > will be very helpful for developing and tweaking optimizations in tcg.
OK I'll roll in Richard's comments and re-submit. > > <snip> > >> @@ -2575,6 +2579,8 @@ static inline int tcg_gen_code_common(TCGContext *s, >> uint64_t target_pc, >> the_end: >> /* Generate TB finalization at the end of block */ >> tcg_out_tb_finalize(s); >> + >> + tcg_write_perfmap(gen_code_buf, s->code_ptr - gen_code_buf, target_pc); >> return -1; >> } > > I think a part of the patch is missing here. tcg_gen_code_common does not > have target_pc argument in current master. Ahh yes - it's currently sitting on-top of my qemu-log series which pulled target_pc into the tcg_gen_code_common loop for the -dfilter patch. I'll be sending the updated series in a moment. > <snip> > >> diff --git a/vl.c b/vl.c >> index c036367..f1c3c3d 100644 >> --- a/vl.c >> +++ b/vl.c >> @@ -123,6 +123,9 @@ int main(int argc, char **argv) >> #define MAX_VIRTIO_CONSOLES 1 >> #define MAX_SCLP_CONSOLES 1 >> >> +/* seems better than pulling in all the tcg headers? */ >> +extern void qemu_tcg_enable_perfmap(void); >> + I'm surprised no one has pulled me up on this yet, perhaps it is just less ugly! >> static const char *data_dir[16]; >> static int data_dir_idx; >> const char *bios_name = NULL; >> @@ -3345,6 +3348,9 @@ int main(int argc, char **argv, char **envp) >> case QEMU_OPTION_DFILTER: >> qemu_set_dfilter_ranges(optarg); >> break; >> + case QEMU_OPTION_PERFMAP: >> + qemu_tcg_enable_perfmap(); >> + break; >> case QEMU_OPTION_s: >> add_device_config(DEV_GDB, "tcp::" DEFAULT_GDBSTUB_PORT); >> break; >> > > Is there any particular reason it is not enabled for linux-user mode? I > think it should work just fine in both modes. linux-user handles command > line options by itself in a different manner (and it has it's own set of > options, different from softmmu targets). The corresponding code is in > linux-user/main.c. No real reason. I was only experimenting with system emulation so that's all I'd tested it with. In fact for linux-user we should be able to make a better stab at giving the blocks decent names thanks to symbol-lookup. I'll update the patch to do it. -- Alex Bennée
