On Fri, Jun 22, 2012 at 9:58 AM, Xin Tong <xerox.time.t...@gmail.com> wrote: > It is a pity that QEMU does not outline the TLB lookup code. I do not > know how much impact the inlined TLB code has due to icache misses...
With a test case the impact could be measured. Maybe it could be just a program performing loads in a loop, executing under a user emulator. > Another benefit one gets from outlined TLB code is that it is much > easier to gather the amount of time spent in the TLB. one can just > profile QEMU and count up how many ticks happened in the outlined TLB > translation code. There's also a possible benefit that the code generation buffer does not fill as fast. > In fact, i do not think outlining QEMU inlined TLB lookup is too hard > to implement. one can still keep most of the original inlined TLB code > and use call/ret to get a TLB translation. of course, one needs to > come up with a new linkage. If it can be shown with a test case and statistics that outlining does not make things worse, we can switch. > > Xin > > > On Wed, Jun 20, 2012 at 3:57 AM, 陳韋任 (Wei-Ren Chen) > <che...@iis.sinica.edu.tw> wrote: >> CC'ed to the mailing list. >> >> -- >> Wei-Ren Chen (陳韋任) >> Computer Systems Lab, Institute of Information Science, >> Academia Sinica, Taiwan (R.O.C.) >> Tel:886-2-2788-3799 #1667 >> Homepage: http://people.cs.nctu.edu.tw/~chenwj >> >> >> ---------- Forwarded message ---------- >> From: Orit Wasserman <owass...@redhat.com> >> To: "\"陳韋任 (Wei-Ren Chen)\"" <che...@iis.sinica.edu.tw> >> Cc: >> Date: Tue, 19 Jun 2012 12:01:08 +0300 >> Subject: Re: [Qemu-devel] How to measure guest memory access >> (qemu_ld/qemu_st) time? >> On 06/19/2012 11:49 AM, 陳韋任 (Wei-Ren Chen) wrote: >>> Mind me CC this to ML? :) >> sure I will read the threads to understand more. >> >> Orit >>> >>>> Well it was a while back (2008-9) ,the company was acquired by IBM a year >>>> later : >>>> http://www.linux-kvm.org/wiki/images/9/98/KvmForum2008%24kdf2008_2.pdf >>>> I think stefan Hanjoczi worked there ... >>>> The company used the technology for cross platform guest support but claim >>>> to get speedup too >>>> (for ppc) don't think the speedup was related to mmu but more to the >>>> instruction stream. >>>> I hope this is helpful. >>> >>> Thanks. >>> >>>> Do you have performance result for the cost of the address translation ? >>>> If I understand you are concentrating on ARM ? >>> >>> The whole discussion thread is on [1], and you can get some feel about >>> the cost of address translation here [2]. Yes, ARM is our target right now, >>> but I think we are not limit to it. >>> >>> Regards, >>> chenwj >>> >>> [1] http://www.mail-archive.com/qemu-devel@nongnu.org/msg116159.html >>> [2] http://www.mail-archive.com/qemu-devel@nongnu.org/msg116404.html >>> >> >