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Date: Thu, 04 Dec 2008 16:22:59 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Thomas Gleixner <tglx@...utronix.de> CC: LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>, Stephane Eranian <eranian@...glemail.com>, Eric Dumazet <dada1@...mosbay.com>, Robert Richter <robert.richter@....com>, Arjan van de Veen <arjan@...radead.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Steven Rostedt <rostedt@...dmis.org>, David Miller <davem@...emloft.net>, Paul Mackerras <paulus@...ba.org> Subject: Re: [patch 0/3] [Announcement] Performance Counters for Linux Thomas Gleixner wrote: > > We'd like to announce a brand new implementation of performance counter > support for Linux. It is a very simple and extensible design that has the > potential to implement the full range of features we would expect from such > a subsystem. > First of all, let me say I really like what I've seen so far. The file descriptor paradigm seems really elegant to me. > - Only one single new system call is needed: sys_perf_counter_open(). > All performance-counter operations are implemented via standard > VFS APIs such as read() / fcntl() and poll(). As previously discussed, I think this should be a filesystem rather than a system call. There are a couple of advantages to doing it that way, IMO: - Strings, rather than numbers, which means fewer constraints across architectures. - The events available can be exported in the filesystem itself (via readdir) rather than via sysfs. - Compatibility with existing tools, esp. non-C tools. I'm thinking of something like: /dev/perfctr/3/cache_misses/all/simple/300 i.e. /dev/perfctr/<cpu>/<event>/<pid>/<type>/<period>. I am putting <cpu> ahead of <event> in the hierarchy, so a readdir() on the <cpu> directory can show the events available by name on that CPU. Raw hardware events can be accessed by something like /dev/perfctr/<cpu>/0x4064/... -hpa -- 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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