On Mon 25-09-17 23:55:19, Yang Shi wrote: > > > On 9/25/17 7:23 AM, Michal Hocko wrote: > > On Thu 21-09-17 06:38:50, Yang Shi wrote: > > > Recently we ran into a oom issue, kernel panic due to no killable process. > > > The dmesg shows huge unreclaimable slabs used almost 100% memory, but kdump doesn't capture vmcore due to some reason. > > > > > > So, it may sound better to capture unreclaimable slab info in oom message when kernel panic to aid trouble shooting and cover the corner case. > > > Since kernel already panic, so capturing more information sounds worthy and doesn't bother normal oom killer. > > > > > > With the patchset, tools/vm/slabinfo has a new option, "-U", to show unreclaimable slab only. > > > > > > And, oom will print all non zero (num_objs * size != 0) unreclaimable slabs in oom killer message. > > > > Well, I do undestand that this _might_ be useful but it also might > > generates a _lot_ of output. The oom report can be quite verbose already > > so is this something we want to have enabled by default? > > The uneclaimable slub message will be just printed out when kernel panic (no > killable process or panic_on_oom is set). So, it will not bother normal oom. > Since kernel is already panic, so it might be preferred to have more > information reported. Well, this certainly depends. If you have a limited console output (e.g. no serial console) then the additional information can easily scroll the potentially much more useful information from the early oom report. We already do have a control to enable/disable tasks dumping which can be very long as well. > We definitely can add a proc knob to control it if we want to disable the > message even if when kernel panic. Well, I do not have a strong opinion on this. I can see cases where this kind of information would be useful but most OOM reports I have seen were simply user space pinned memory. Slab memory leaks are seen very seldom. Do you think a pr_dbg and slab stats for all ooms would be still useful? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
