Date: Fri, 26 May 2006 20:48:21 +0530 From: "Joseph Koshy" <joseph.koshy@gmail.com> To: "gnn@freebsd.org" <gnn@freebsd.org> Cc: John Birrell <jb@what-creek.com>, current@freebsd.org Subject: Re: DTrace for FreeBSD - Status Update Message-ID: <84dead720605260818t7460cd6dp5de7311a1b5edc28@mail.gmail.com> In-Reply-To: <m264jt2mjw.wl%gnn@neville-neil.com> References: <20060525065510.GA20475@what-creek.com> <m264jt2mjw.wl%gnn@neville-neil.com>
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> But, I have a naive question. Should this be integrated in > some way with the hwpmc work of Joseph Koshy since I think it > could be useful for DTRace to get information from the CPU as > well. Disclaimer: I've only just started reading about DTrace. There appear to be two ways to integrate hwpmc and DTrace: - Augment the D virtual machine with a primitive that can read PMC values (e.g.- using RDPMC or RDMSR instructions on x86 CPUs). Make this primitive available to scripts for allocating and reading from PMCs (say a "pmcread()" builtin function). This approach would work well with counting mode PMCs (both process and system-mode counting PMCs) and would allow PMCs to be read at arbitrary points of time. We'll need a way of allocating system-wide & process-mode PMCs; this could be done in userland (in dtrace(8)). - hwpmc(4) can be augmented to be a 'DTrace provider' allowing D scripts to be run, say when a PC sample is recorded. -- FreeBSD Developer, http://people.freebsd.org/~jkoshy
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