|From:||Ingo Molnar <mingo-AT-elte.hu>|
|To:||Avi Kivity <avi-AT-redhat.com>|
|Subject:||Re: [RFC] Unify KVM kernel-space and user-space code into a single project|
|Date:||Mon, 22 Mar 2010 12:23:40 +0100|
|Cc:||Anthony Liguori <anthony-AT-codemonkey.ws>, Pekka Enberg <penberg-AT-cs.helsinki.fi>, "Zhang, Yanmin" <yanmin_zhang-AT-linux.intel.com>, Peter Zijlstra <a.p.zijlstra-AT-chello.nl>, Sheng Yang <sheng-AT-linux.intel.com>, linux-kernel-AT-vger.kernel.org, kvm-AT-vger.kernel.org, Marcelo Tosatti <mtosatti-AT-redhat.com>, oerg Roedel <joro-AT-8bytes.org>, Jes Sorensen <Jes.Sorensen-AT-redhat.com>, Gleb Natapov <gleb-AT-redhat.com>, Zachary Amsden <zamsden-AT-redhat.com>, ziteng.huang-AT-intel.com, Arnaldo Carvalho de Melo <acme-AT-redhat.com>, Fr?d?ric Weisbecker <fweisbec-AT-gmail.com>|
* Avi Kivity <email@example.com> wrote: > IMO the reason perf is more usable than oprofile has less to do with the > kernel/userspace boundary and more do to with effort and attention spent on > the userspace/user boundary. > > [...] If you are interested in the first-hand experience of the people who are doing the perf work then here it is: by far the biggest reason for perf success and perf usability is the integration of the user-space tooling with the kernel-space bits, into a single repository and project. The very move you are opposing so vehemently for KVM. Oprofile went the way you proposed, and it was a failure. It failed not because it was bad technology (it was pretty decent and people used it), it was not a failure because the wrong people worked on it (to the contrary, very capable people worked on it), it was a failure in hindsight because it simply incorrectly split into two projects which stiffled the progress of each other. Obviously 3 years ago you'd have seen a similar, big "Oprofile is NOT broken!" flamewar, had i posted the same observations about Oprofile that i expressed about KVM here. (In fact there was a similar, big flamewar about all this when perf was posted a year ago.) And yes, (as you are aware of) i see very similar patterns of inefficiency in the KVM/Qemu tooling relationship as well, hence did i express my views about it. Thanks, Ingo
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