On Tue, Feb 18, 2020 at 09:17:10AM -0500, Josef Bacik wrote: > On 2/17/20 11:38 AM, Brian Foster wrote: > > On Fri, Feb 14, 2020 at 03:34:31PM -0500, Josef Bacik wrote: > > > I want to add some extended statistic gathering for xfstests, but it's > > > tricky to isolate xfstests from the rest of the host applications. The > > > most straightforward way to do this is to run every test inside of it's > > > own cgroup. From there we can monitor the activity of tasks in the > > > specific cgroup using BPF. > > > > > > > I'm curious what kind of info you're looking for from tests.. > > > > Latencies. We have all of these tests doing all sorts of interesting > things, I want to track operation latencies with code we're actually testing > so I can see if I've introduced a performance regression somewhere. Since > Facebook's whole fleet is on btrfs I want to make sure I'm only getting > information from things being run by xfstests so I can easily go back and > hunt down regressions that get introduced. With BPF I can filter on cgroup > membership, so I know I'm only recording stats I care about. > Interesting, might be useful to document the use case in the commit log. > > > The support for this is pretty simple, allow users to specify > > > CGROUP=/path/to/cgroup. We will create the path if it doesn't already > > > exist, and validate we can add things to cgroup.procs. If we cannot > > > it'll be disabled, otherwise we will use this when we do _run_seq by > > > echo'ing the bash pid into cgroup.procs, which will cause any children > > > to run under that cgroup. > > > > > > > Seems reasonable, but is there any opportunity to combine this with what > > we have in common/cgroup2? It's not clear to me if this cares about > > cgroup v1 or v2, but perhaps the cgroup2 checks could be built on top of > > a generic CGROUP var? I'm also wondering if we'd want to change runtime > > behavior purely based on the existence of the path as opposed to some > > kind of separate knob (in the event some future test requires the path > > for some reason without wanting to enable this mechanism). > > > > Oh I probably should have looked around, yeah we can definitely use this. > My initial thought is to just make CGROUP2_PATH exported always, we create > /path/to/cgroup2/xfstests and point CGROUP2_PATH at that, and then any tests > that use the cgroup2 path for their test will automatically be populated > under that global xfstests directory, so I can still capture them with my > scripts. Does that sound reasonable? Thanks, > Not sure I follow.. are you saying that we'd change CGROUP2_PATH from simply pointing at the local cgroup2 root on the local box to some magic field that directs creation of a cgroup for the particular test? Or did you mean to use a different variable name in the second case? Maybe it's just easier to see a patch... Brian > Josef >
