On Mon, Jun 22, 2020 at 11:25 AM Roman Gushchin <guro@xxxxxx> wrote: > > On Mon, Jun 22, 2020 at 11:09:47AM -0700, Shakeel Butt wrote: > > 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. > > To me it's a perfect example where tools like drgn and bpf shine. > They are more flexible and do not blow the kernel up with > the debug-only code. > > > > > > 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? > > To be precise, not over all RAM, but over all struct pages. > Unfortunately, there is no better option with SLUB, as there is no > comprehensive list of slab pages available. So the only option is to scan > over all pages with PageSlab flag set. > So, SLUB does not have any field available in the struct page to support the list of slab pages? Anyways, that's a separate discussion. Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
