On 2015/07/21 13:34, Ananth N Mavinakayanahalli wrote: > On Tue, Jul 21, 2015 at 12:53:07PM +1000, Michael Ellerman wrote: >> On Sun, 2015-07-19 at 11:21 +0900, Masami Hiramatsu wrote: >>> On 2015/07/16 19:56, Ananth N Mavinakayanahalli wrote: >>>> Kprobes uses a breakpoint instruction to trap into execution flow >>>> and the probed instruction is single-stepped from an alternate location. >>>> >>>> On some architectures like x86, under certain conditions, the OPTPROBES >>>> feature enables replacing the probed instruction with a jump instead, >>>> resulting in a significant perfomance boost (one single-step exception >>>> is bypassed for each kprobe). >>> >>> The OPTPROBE is not only for bypassing the single-step exception, but also >>> the breakpoint exception. >>> Please see commit 0dc016dbd820260b (ARM: kprobes: enable OPTPROBES for ARM >>> 32) too, >>> which shows how it is done on RISC processor. >>> >>>> Powerpc has an in-kernel instruction emulator. Kprobes on powerpc uses >>>> this emulator already and bypasses the single-step exception, with a >>>> lot less complexity. >>> >>> So, this might miss the point. Since it is impossible to do on some RISC >>> processor, I agree with this change, but it should be committed with >>> correct comments. >> >> I don't think it's impossible on powerpc. >> >> So we should leave it as a TODO for now. > > OK. I put it on my TODO list.
I see, thanks Ananth! :) -- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu...@hitachi.com _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
