On Mon, Jun 22, 2020 at 11:02 AM Roman Gushchin <guro@xxxxxx> wrote: > > On Mon, Jun 22, 2020 at 10:12:46AM -0700, Shakeel Butt wrote: > > On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@xxxxxx> wrote: > > > > > > Deprecate memory.kmem.slabinfo. > > > > > > An empty file will be presented if corresponding config options are > > > enabled. > > > > > > The interface is implementation dependent, isn't present in cgroup v2, > > > and is generally useful only for core mm debugging purposes. In other > > > words, it doesn't provide any value for the absolute majority of users. > > > > > > A drgn-based replacement can be found in tools/cgroup/slabinfo.py . > > > It does support cgroup v1 and v2, mimics memory.kmem.slabinfo output > > > and also allows to get any additional information without a need > > > to recompile the kernel. > > > > > > If a drgn-based solution is too slow for a task, a bpf-based tracing > > > tool can be used, which can easily keep track of all slab allocations > > > belonging to a memory cgroup. > > > > > > Signed-off-by: Roman Gushchin <guro@xxxxxx> > > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > > Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> > > > > Hi Roman, > > > > I am not against removing the memory.kmem.slabinfo interface but I > > would like to have an alternative solution more accessible than > > tools/cgroup/slabinfo.py. > > > > In our case, we don't have ssh access and if we need something for > > debugging, it is much more preferable to provide a file to read to > > SREs. After the review, that file will be added to a whitelist and > > then we can directly read that file through automated tools without > > approval for each request. > > > > I am just wondering if a file interface can be provided for whatever > > tools/cgroup/slabinfo.py is providing. > > > > Shakeel > > Hello, Shakeel! > > I understand your point, but Idk how much we wanna make this code a part > of the kernel and the cgroup interface. No need for the cgroup interface. I was thinking of a new interface like /proc/slabinfo_full which tells active objects for each kmem_cache and memcg pair. > The problem is that reading > from it will be really slow in comparison to all other cgroup interface > files. Idk if Google's version of SLAB has a list of all slab pages, > but if not (as in generic SLUB case), it requires scanning of the whole RAM. That's a bummer. Does drgn-based script scan the whole RAM?
