[Qemu-devel] [RFC 0/7] tcg: parallel code generation (Work in Progress)

[Emilio G. Cota]

This is a request for comments as well as a request for help :-)

I've been experimenting with making TCGContext per-thread, so that we can
run most of tcg_gen_code in parallel. I've made some progress,
but haven't yet got it to work.

My guess is that the TCG stack is still global instead of per-vCPU
(it's been global since tmp_buf was removed from CPUState, right?),
but I'm having trouble following that code so most likely I'm wrong.

Any help would be appreciated--please disregard minor nits, I want
to see whether I can make this work to then take measurements
to decide whether this is worth the trouble.

- Patch 1 is a trivial doc fixup, feel free to pick it up

- Patches 2-3 remove *tbs[] to use a binary search tree instead.
  This removes the assumption in tb_find_pc that *tbs[] are ordered
  by tc_ptr, thereby allowing us to generate code regardless of
  its location on the host (as we do after patch 6).

- Patch 4 addresses a reporting issue: ever since we embedded the
  struct TB's in code_gen_buffer (6e3b2bfd6), we have been
  misreporting the size of the generated code. Not a huge deal,
  but I noticed while I was working on this.

- Patches 5-7 make TCGContext per-thread in softmmu. I have put there
  some XXX's to note that I'm aware of those issues, so don't worry
  too much about those--except of course if you have any input on
  what the cause of the race(s) might be.

Thanks,

                Emilio