Messages in this thread | | | Date | Fri, 09 Apr 2010 16:36:24 -0400 | From | Masami Hiramatsu <> | Subject | Re: [PATCH 0/9] jump label v6 |
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Hi Jason,
Jason Baron wrote: > Hi, > > Refresh of jump labeling patches aginst -tip tree. For bacground see: > http://marc.info/?l=linux-kernel&m=125858436505941&w=2 > > I believe I've addressed all the reviews from v5. > > Changes in v6: > > * I've moved Steve Rostedt's 'ftrace_dyn_arch_init()' to alternative.c to > put it into a common area for used by both ftrace and jump labels. By > default we put a 'jmp 5' in the nop slot. Then, when we detect the best > runtime no-op we patch over the 'jmp 5' with the appropriate nop. > > * build time sort of the jump label table. The jump label table is more > optimally accessed if the entries are continguous. Sorting the table > accomplishes this. Do the sort at build-time. Adds a '-j' option to > 'modpost' which replaces the vmlinux, with a sorted jump label section vmlinux. > I've tested this on x86 with relocatable and it works fine there as well. Note > that I have not sorted the jump label table in modules. This is b/c the jump > label names can be exported by the core kernel, and thus I don't have them > available at buildtime. This could be solved by either finding the correct > ones in the vmlinux, or by embedding the name of the jump label in the module > tables (and not just a pointer), but the module tables tend to be smaller, and > thus there is less value to this kind of change anyway. The kernel continues to > do the sort, just in case, but at least for the vmlinux, this is just a > verfication b/c the jump label table has already been sorted. > > * added jump_label_text_reserved(), so that other routines that want to patch > the code, can first verify that they are not stomping on jump label addresses.
Good!:-) So now, it might be a good time to integrate those text_reserved() functions.
BTW, how many jumps would you expect modifying at once? Since the text_poke_smp() uses stop_machine() for each modifying text, I found that it can cause a delay issue if it is called so many times... (e.g. a systemtap testcase sets ~5000 probes at once)
Thank you,
-- Masami Hiramatsu e-mail: mhiramat@redhat.com
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