Allow different tracers to be compiled independently
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From: Theodore Tso on 22 Mar 2010 23:50 On Mar 22, 2010, at 9:04 PM, Frederic Weisbecker wrote: > > I don't know. Yeah this first looks like a good idea but once > CONFIG_EVENT_TRACING is enabled, each tracepoint is a lightweight > thing and induce a tiny overhead, probably hard to notice, and > this is going to be even more the case after the jmp label > optimization patches. > > I liked the fact we had a general tracing kernel once the above > config is selected. And we don't bother telling people that to > use tool X you need CONFIG_EVENT_Y, and you need to rebuild your > kernel, etc... Indeed, a lot of the value of tracepoints goes away if people are compiling kernels without them and we need to get a special "tracing kernel" installed before we can debug a problem. So I'd hope we can do the necessary optimization work so people don't feel it's necessary to enable or disable tracepoints by subsystem.... -- Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Ingo Molnar on 23 Mar 2010 04:10
* Theodore Tso <tytso(a)MIT.EDU> wrote: > > On Mar 22, 2010, at 9:04 PM, Frederic Weisbecker wrote: > > > > I don't know. Yeah this first looks like a good idea but once > > CONFIG_EVENT_TRACING is enabled, each tracepoint is a lightweight thing > > and induce a tiny overhead, probably hard to notice, and this is going to > > be even more the case after the jmp label optimization patches. > > > > I liked the fact we had a general tracing kernel once the above config is > > selected. And we don't bother telling people that to use tool X you need > > CONFIG_EVENT_Y, and you need to rebuild your kernel, etc... > > Indeed, a lot of the value of tracepoints goes away if people are compiling > kernels without them and we need to get a special "tracing kernel" installed > before we can debug a problem. > > So I'd hope we can do the necessary optimization work so people don't feel > it's necessary to enable or disable tracepoints by subsystem.... Yeah, agreed. Ultra-embedded can disable them all, but other than that i think we should not make it too finegrained as a lot of tooling value is in the 'critical mass' that tracepoints have achieved. The power events tracepoints are most useful when combined with scheduling events, etc. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |