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Date: Fri, 03 Feb 2012 11:30:29 +0800 From: Yanmin Zhang <yanmin_zhang@...ux.intel.com> To: Stephane Eranian <eranian@...gle.com> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>, linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu, robert.richter@....com, Avi Kivity <avi@...hat.com> Subject: Re: [PATCH] perf: fix broken perf inject -b On Thu, 2012-02-02 at 12:22 +0100, Stephane Eranian wrote: > On Tue, Jan 31, 2012 at 6:58 AM, Yanmin Zhang > <yanmin_zhang@...ux.intel.com> wrote: > > On Mon, 2012-01-30 at 18:36 -0200, Arnaldo Carvalho de Melo wrote: > >> Em Mon, Jan 30, 2012 at 09:09:17PM +0100, Stephane Eranian escreveu: > >> > On Mon, Jan 30, 2012 at 9:04 PM, Arnaldo Carvalho de Melo > >> > <acme@...hat.com> wrote: > >> > > Em Mon, Jan 30, 2012 at 08:53:26PM +0100, Stephane Eranian escreveu: > >> > >> On Mon, Jan 30, 2012 at 8:00 PM, Arnaldo Carvalho de Melo > >> > >> <acme@...hat.com> wrote: > >> > >> > > >>> @@ -173,6 +178,7 @@ static int perf_event__inject_buildid(struct perf_tool *tool, > >> > >> > > >>> goto repipe; > >> > >> > > >>> } > >> > >> > > >>> + machine->pid = event->ip.pid; > >> > >> > > >> > >> > > I noticed that this statement conflicts with perf buildid-list (which > >> > >> > > I am also fixing for pipe mode). > >> > >> > >> > > I don't quite understand why, though. > >> > >> > >> > Have you reached any conclusion about this problem? I haven't looked at > >> > >> > it in detail, could you please elaborate more? > >> > >> > >> I ended up removing it. But I am not sure this is correct. > >> > >> Is the pid used in any way when processing buildids? > >> > > > >> > > I can't think of any. > >> > > > >> > > The same DSO could conceivably be present in the virtual machine, the > >> > > host, and in the workstation used for perf report. We just use the > >> > > build-id in the perf.data file to find the right symtab. > >> > >> > Right, so I don't know why it's there... > >> > >> This comes from a1645ce1: > >> > >> commit a1645ce12adb6c9cc9e19d7695466204e3f017fe > >> Author: Zhang, Yanmin <yanmin_zhang@...ux.intel.com> > >> Date: Mon Apr 19 13:32:50 2010 +0800 > >> > >> perf: 'perf kvm' tool for monitoring guest performance from host > >> > >> Here is the patch of userspace perf tool. > >> > >> Signed-off-by: Zhang Yanmin <yanmin_zhang@...ux.intel.com> > >> Signed-off-by: Avi Kivity <avi@...hat.com> > >> > >> > >> > >> Zhang, what was the thinking about that pid in the buildid event? > > I didn't work on it for a long time because of some special reasons. > > I check it quickly and below are some explanation. > > > > machine->pid is to support KVM multiple guest os kernels. > > 1) The guest os kernels might be different version of kernels from host's; > > 2) The guest os might be Windows. > > > I understand that. > > > At host side, every guest os is a process of host although it's multi-threaded. > Yes. > > machine->pid is to save its pid. The pid of host itself is HOST_KERNEL_ID. > > > What do you mean by the 'pid of the host'? You always capture samples on the > host on behalf of a host task. I see PID:-1 to simulate mmap of the kernel in > the perf.data file. Is that what you are referring to? Yes. > > > In guest os, there are many processes. host os doesn't know them. So currently or > > Yes. > > > when I enhanced perf to support KVM, perf filters out guest os user space > > detailed event samples while still keeping guest os user space simple counters. > > > That is not clear to me. Are you saying, you have no visibility into > the guest OS > user space processes, samples captured at that level are attributed to > guest kernel? > Or are you simply dropping them? It depends specific perf subcommand. 1) With per top, besides the specific function symbol statistics, it also shows the total percent of host_kernel/host_user/guest_kernel/guest_user. With the function symbol statistics, we drop guest user space data. With the total percent, we keep them into the calculation of guest user. static void perf_top__mmap_read_idx(struct perf_top *top, int idx) { ... case PERF_RECORD_MISC_GUEST_USER: ++top->guest_us_samples; /* * TODO: we don't process guest user from host side * except simple counting. */ /* Fall thru */ default: continue; } ... } 2) With other subcommands, it seems perf would drop guest user space statistics. Sorry for my old memory. > > > event->ip.pid is equal to machine->pid only when > > ((event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK) == PERF_RECORD_MISC_GUEST_KERNEL). > > > > In function perf_event__inject_buildid, we shouldn't reset machine->pid to > > event->ip.pid. They are equal to each other if it's a guest os event. Isn't it? > > I have not tried capturing samples on a kvm process. So I don't know. There is a local team here working on performance tuning/benchmarking. They use 'perf kvm' to collect/analyze their guest os performance. -- 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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