On Sat, Nov 25, 2023 at 11:01:37AM +0300, Dmitry Rokosov wrote: [...] > > > + trace_mm_vmscan_memcg_shrink_begin(sc->order, > > > + sc->gfp_mask, > > > + memcg); > > > + > > > > If you place the start of the trace here, you may have only the begin > > trace for memcgs whose usage are below their min or low limits. Is that > > fine? Otherwise you can put it just before shrink_lruvec() call. > > > > From my point of view, it's fine. For situations like the one you > described, when we only see the begin() tracepoint raised without the > end(), we understand that reclaim requests are being made but cannot be > satisfied due to certain conditions within memcg (such as limits). > > There may be some spam tracepoints in the trace pipe, which is a disadvantage > of this approach. > > How important do you think it is to understand such situations? Or do > you suggest moving the begin() tracepoint after the memcg limits checks > and don't care about it? > I was mainly wondering if that is intentional. It seems like you as first user of this trace has a need to know that a reclaim for a given memcg was triggered but due to min/low limits no reclaim was done. This is a totally reasonable use-case.
