Messages in this thread | | | Date | Wed, 15 Jul 2015 14:47:41 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH] perf: Container-aware tracing support |
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On Wed, Jul 15, 2015 at 02:38:36PM +0530, Aravinda Prasad wrote: > Current tracing infrastructure such as perf and ftrace reports system > wide data when invoked inside a container. It is required to restrict > events specific to a container context when such tools are invoked > inside a container. > > This RFC patch supports filtering container specific events, without > any change in the user interface, when invoked within a container for > the perf utility; such support needs to be extended to ftrace. This > patch assumes that the debugfs is available within the container and > all the processes running inside a container are grouped into a single > perf_event subsystem of cgroups. This patch piggybacks on the existing > support available for tracing with cgroups [1] by setting the cgrp > member of the event structure to the cgroup of the context perf tool > is invoked from. > > However, this patch is not complete and requires more work to fully > support tracing inside a container. This patch is intended to initiate > the discussion on having container-aware tracing support. A detailed > explanation on what is supported and pending issues are mentioned > below.
tracing is outside the scope of perf; I suspect you want tracefs to be sensitive to filesystem namespaces and all that that entails.
> Cc: Hari Bathini <hbathini@linux.vnet.ibm.com> > Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com> > --- > kernel/events/core.c | 49 +++++++++++++++++++++++++++++++++++-------------- > 1 file changed, 35 insertions(+), 14 deletions(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 81aa3a4..f6a1f89 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -589,17 +589,38 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, > { > struct perf_cgroup *cgrp; > struct cgroup_subsys_state *css; > - struct fd f = fdget(fd); > + struct fd f; > int ret = 0; > > - if (!f.file) > - return -EBADF; > + if (fd != -1) { > + f = fdget(fd); > + if (!f.file) > + return -EBADF; > > - css = css_tryget_online_from_dir(f.file->f_path.dentry, > + css = css_tryget_online_from_dir(f.file->f_path.dentry, > &perf_event_cgrp_subsys); > - if (IS_ERR(css)) { > - ret = PTR_ERR(css); > - goto out; > + if (IS_ERR(css)) { > + ret = PTR_ERR(css); > + fdput(f); > + return ret; > + } > + } else if (event->attach_state == PERF_ATTACH_TASK) { > + /* Tracing on a PID. No need to set event->cgrp */ > + return ret; > + } else if (task_active_pid_ns(current) != &init_pid_ns) {
Why the pid namespace?
> + /* Don't set event->cgrp if task belongs to root cgroup */ > + if (task_css_is_root(current, perf_event_cgrp_id)) > + return ret;
So if you have the root perf_cgroup inside your container you can escape?
> + > + css = task_css(current, perf_event_cgrp_id); > + if (!css || !css_tryget_online(css)) > + return -ENOENT; > + } else { > + /* > + * perf invoked from global context and hence don't set > + * event->cgrp as all the events should be included > + */ > + return ret; > } > > cgrp = container_of(css, struct perf_cgroup, css);
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