[CRIU] [PATCH] Skip restoring certain cgroup root directories when using full mode
Hui Kang
hkang.sunysb at gmail.com
Tue Aug 18 14:40:21 PDT 2015
On Tue, Aug 18, 2015 at 11:13 AM, Pavel Emelyanov <xemul at parallels.com>
wrote:
> On 08/18/2015 12:55 AM, Hui Kang wrote:
> > On Mon, Aug 17, 2015 at 10:48 AM, Pavel Emelyanov <xemul at parallels.com>
> wrote:
> >> On 08/17/2015 08:07 AM, Hui Kang wrote:
> >>> On Sun, Aug 16, 2015 at 9:20 PM, Pavel Emelyanov <xemul at parallels.com>
> wrote:
> >>>> On 08/13/2015 07:41 PM, Hui Kang wrote:
> >>>>> Skip these top cgroup directories: cpu, cpuset, cpuacct, memory
> >>>>>
> >>>>> Signed-off-by: Hui Kang <hkang.sunysb at gmail.com>
> >>>>> ---
> >>>>> cgroup.c | 4 ++++
> >>>>> 1 file changed, 4 insertions(+)
> >>>>>
> >>>>> diff --git a/cgroup.c b/cgroup.c
> >>>>> index a4e0146..94749b1 100644
> >>>>> --- a/cgroup.c
> >>>>> +++ b/cgroup.c
> >>>>> @@ -992,6 +992,10 @@ static int prepare_cgroup_dir_properties(char
> *path, int off, CgroupDirEntry **e
> >>>>> CgroupDirEntry *e = ents[i];
> >>>>> size_t off2 = off;
> >>>>>
> >>>>> + if (strcmp(e->dir_name, "") == 0 &&
> >>>>> + ((strstr(path, "cpu")) || (strstr(path,
> "memory"))))
> >>>>> + continue;
> >>>>> +
> >>>>
> >>>> With this "continue" won't we skip all the properties restore? The
> e-s we
> >>>> have here represent all the tree, starting from root and descending.
> If you
> >>>> skip the root one, then the whole subtree is skipped too.
> >>>
> >>> No. Although the e-s represent the tree, the for loops will iterate
> >>> all the directories.
> >>
> >> The loop iterates top-level directories, then dives into children. Can
> you show
> >> the contents of your cgroup.img file?
> >
> > {
> > "magic": "CGROUP",
> > "entries": [
>
> Ah, I see. The thing is that in your case you don't have nested
> directories. In
> particular -- cpuset is only the "foo/foo1" dir, so your check doesn't
> match
> one and it's restored. The cpu/cpuacct are both "/" only, so you check
> matches
> them, skips, but we notice nothing as there are no sub-directories.
>
HI, Pavel,
can you give me an example which has nested directories? I added the
process to foo/foo1/tasks and then dump the process. So no value in foo is
dumped.
For a nested cgroup directory, do you mean I should also add a parent tasks
to foo and then dump both parent and child?
>
> And for the same reason restore-special-props works OK -- the cpuset
> controller
> is "foo/foo1", so it gets restored successfully.
>
> So my concern about the wrong place for strcmp(name, "") check still
> stands.
>
If you could give me an counter example like nested directory, it will
helpful to fix this check. Thanks.
- Hui
>
> -- Pavel
>
> > {
> > "sets": [
> > {
> > "id": 2,
> > "ctls": [
> > {
> > "name": "blkio",
> > "path": "/"
> > },
> > {
> > "name": "cpu",
> > "path": "/"
> > },
> > {
> > "name": "cpuacct",
> > "path": "/"
> > },
> > {
> > "name": "cpuset",
> > "path": "/foo/foo1"
> > },
> > {
> > "name": "devices",
> > "path": "/"
> > },
> > {
> > "name": "freezer",
> > "path": "/"
> > },
> > {
> > "name": "hugetlb",
> > "path": "/"
> > },
> > {
> > "name": "memory",
> > "path": "/"
> > },
> > {
> > "name": "name=systemd",
> > "path": "/"
> > },
> > {
> > "name": "perf_event",
> > "path": "/"
> > }
> > ]
> > }
> > ],
> > "controllers": [
> > {
> > "cnames": [
> > "cpuset"
> > ],
> > "dirs": [
> > {
> > "dir_name": "foo/foo1",
> > "properties": [
> > {
> > "name": "cpuset.cpus",
> > "value": "1"
> > },
> > {
> > "name": "cpuset.mems",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.memory_migrate",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.cpu_exclusive",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.mem_exclusive",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.mem_hardwall",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.memory_spread_page",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.memory_spread_slab",
> > "value": "0"
> > },
> > {
> > "name": "cpuset.sched_load_balance",
> > "value": "1"
> > },
> > {
> > "name":
> "cpuset.sched_relax_domain_level",
> > "value": "-1"
> > },
> > {
> > "name": "notify_on_release",
> > "value": "0"
> > }
> > ]
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "cpu"
> > ],
> > "dirs": [
> > {
> > "dir_name": "",
> > "properties": [
> > {
> > "name": "cpu.shares",
> > "value": "1024"
> > },
> > {
> > "name": "cpu.cfs_period_us",
> > "value": "100000"
> > },
> > {
> > "name": "cpu.cfs_quota_us",
> > "value": "-1"
> > },
> > {
> > "name": "notify_on_release",
> > "value": "0"
> > }
> > ]
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "cpuacct"
> > ],
> > "dirs": [
> > {
> > "dir_name": ""
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "memory"
> > ],
> > "dirs": [
> > {
> > "dir_name": "",
> > "properties": [
> > {
> > "name": "memory.limit_in_bytes",
> > "value": "-1"
> > },
> > {
> > "name": "memory.use_hierarchy",
> > "value": "0"
> > },
> > {
> > "name": "notify_on_release",
> > "value": "0"
> > }
> > ]
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "devices"
> > ],
> > "dirs": [
> > {
> > "dir_name": ""
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "freezer"
> > ],
> > "dirs": [
> > {
> > "dir_name": "",
> > "properties": [
> > {
> > "name": "notify_on_release",
> > "value": "0"
> > }
> > ]
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "blkio"
> > ],
> > "dirs": [
> > {
> > "dir_name": "",
> > "properties": [
> > {
> > "name": "blkio.weight",
> > "value": "1000"
> > },
> > {
> > "name": "notify_on_release",
> > "value": "0"
> > }
> > ]
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "perf_event"
> > ],
> > "dirs": [
> > {
> > "dir_name": ""
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "hugetlb"
> > ],
> > "dirs": [
> > {
> > "dir_name": ""
> > }
> > ]
> > },
> > {
> > "cnames": [
> > "name=systemd"
> > ],
> > "dirs": [
> > {
> > "dir_name": ""
> > }
> > ]
> > }
> > ]
> > }
> > ]
> > }
> >
> >>
> >>> With "full" mode, the top "cpu" and "mem"
> >>> directories should be skipped. The first condition
> >>> (strcmp(e->dir_name, "") guarantees that non-root directory will be
> >>> restored. For a dumped process with cgroup tree "cpuset/foo/foo1". The
> >>> restore process with "full" mode is like
> >>>
> >>> (00.046731) cg: Restored cgroup property value 1 to
> cpuset/foo/foo1/cpuset.cpus
> >>>
> >>> (00.046803) cg: Restored cgroup property value 0 to
> cpuset/foo/foo1/cpuset.mems
> >>>
> >>> ... (after all foo1 properties are restore, the it moves to the top
> level)
> >>>
> >>> (00.047287) cg: ---> Skip Empty name for top path cpu , top dir
> >>>
> >>> As you can see, the patch will only skip those root directories.
> >>>
> >>> One side observations is that the property values of the intermediate
> >>> level (e.g., cpuset/foo) is not dumpped. I confirmed this by running
> >>> crit decode -i cgroup.img --pretty. So when restoring, I have to
> >>> manually create cpuset/foo and populate the value. Is this a bug of
> >>> CRIU?
> >>
> >> CRIU only messes with the cgroups tasks live in, so if they don't live
> >> in foo/ then foo will not be restored. And now it seems strange to me
> >> that the root one is being restored by criu.
> >
> > When you use "--mange-cgroup=full", criu will try to restore
> > /sys/fs/cgroup/cpusets/cpuset.cpus, which is not supposed to be
> > written.
> > But this will not happen with the default "soft" mode; the code sets
> > n_properties = 0.
> >
> > if (opts.manage_cgroups & (CG_MODE_SOFT | CG_MODE_NONE)) {
> > pr_info("Skip restoring properties on
> > cgroup dir %s\n", paux);
> > if (e->n_properties > 0) {
> > xfree(e->properties);
> > e->properties = NULL;
> > e->n_properties = 0;
> > }
> > }
> >
> > - Hui
> >
> >>
> >> -- Pavel
> >>
> > .
> >
>
>
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