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Date: Tue, 02 Mar 2010 19:35:54 -0500 From: Masami Hiramatsu <mhiramat@...hat.com> To: Mathieu Desnoyers <compudj@...stal.dyndns.org> CC: Ingo Molnar <mingo@...e.hu>, Frederic Weisbecker <fweisbec@...il.com>, Ananth N Mavinakayanahalli <ananth@...ibm.com>, lkml <linux-kernel@...r.kernel.org>, systemtap <systemtap@...rces.redhat.com>, DLE <dle-develop@...ts.sourceforge.net>, Jim Keniston <jkenisto@...ibm.com>, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Christoph Hellwig <hch@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, "H. Peter Anvin" <hpa@...or.com>, Anders Kaseorg <andersk@...lice.com>, Tim Abbott <tabbott@...lice.com>, Andi Kleen <andi@...stfloor.org>, Jason Baron <jbaron@...hat.com> Subject: Re: [PATCH -tip v3&10 02/18] kprobes: Introduce generic insn_slot framework Mathieu Desnoyers wrote: > * Masami Hiramatsu (mhiramat@...hat.com) wrote: >> Masami Hiramatsu wrote: >>> Mathieu Desnoyers wrote: >>>> * Masami Hiramatsu (mhiramat@...hat.com) wrote: >>>>> Make insn_slot framework support various size slots. >>>>> Current insn_slot just supports one-size instruction buffer slot. However, >>>>> kprobes jump optimization needs larger size buffers. >>>> >>>> OK, so you end up having one insn slot cache for kprobes and one insn >>>> slot (eventually) for the static jump patching (which needs larger >>>> instruction slots than kprobes). That seems like a good way to ensure >>>> you do not use more memory than necessary. >>>> >>>> We could possibly go even further and automatically use the right insn >>>> slot cache given the size of the instruction entry that must be added (a >>>> bit like the memory allocator which have different pools for each >>>> allocation order). >>> >>> Sure, that will be simpler interface. >>> >>>> Possibly that using the terminology of "memory pools" rather than >>>> "cache" could be a better fit too. So what this really becomes is an >>>> instruction slot allocator and garbage collector. >>> >>> Ah, right. It would be better to rename kprobe_insn_pool() :) >> >> Hmm, I tried it. And finally, I found that this doesn't help >> to simplify code... Maybe it is better to postpone it until >> another user needs this feature. > > I guess it's a tradeoff between the genericity of the API you provide > and the complexity of the code that provides this API. So as you say, > maybe it's better to wait until more users appears before improving the > API. OK, I'll hold that generalizing patch until that. :) Thank you, -- Masami Hiramatsu e-mail: mhiramat@...hat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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