Messages in this thread | | | Subject | Re: [PATCH v2 1/8] x86: speed up int3-based patching using less paranoid write | From | Petr Mladek <> | Date | Tue, 12 Nov 2013 11:44:32 +0100 |
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Steven Rostedt píše v Pá 08. 11. 2013 v 07:43 -0500: > On Fri, 08 Nov 2013 21:04:26 +0900 > Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote: > > > (2013/11/08 18:12), Petr Mladek wrote: > > > This change is inspired by the int3-based patching code used in > > > ftrace. See the commit fd4363fff3d9 (x86: Introduce int3 > > > (breakpoint)-based instruction patching). > > > > > > When trying to use text_poke_bp in ftrace, the result was slower than > > > the original implementation. > > > > > > It turned out that one difference was in text_poke vs. ftrace_write. > > > text_poke did many extra operations to make sure that the change > > > was atomic. > > > > AFAIK, the main reason why text_poke is used is avoiding > > RODATA protection (by alias mapping). > > That is correct, and the reason ftrace didn't do that is because it > would be quite expensive to map 22,000 addresses for each change.
I see. I am going to prepare v3 with the following changes:
+ use text_poke in text_poke_bp back again because it is not effective to make the pages rw only for a single address; the alias mapping is faster here
+ use the faster text_poke_part only in text_poke_bp_iter; the caller of this function will be responsible for making the code rw
+ I will rework the error handling as suggested in the other mails; I will try to add some also for text_poke.
Thanks a lot for hints.
Best Regards, Petr
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