On Fri 30-05-25 11:11:40, David Hildenbrand wrote: > On 30.05.25 11:07, Michal Hocko wrote: > > On Fri 30-05-25 10:39:39, David Hildenbrand wrote: > > > On 30.05.25 10:28, Michal Hocko wrote: > > [...] > > > > All that being said I would go with an additional parameter to the > > > > kdump cma setup - e.g. cma_sane_dma that would skip waiting and use 10s > > > > otherwise. That would make the optimized behavior opt in, we do not need > > > > to support all sorts of timeouts and also learn if this is not > > > > sufficient. > > > > > > > > Makes sense? > > > > > > Just so I understand correctly, you mean extending the "crashkernel=" > > > option > > > with a boolean parameter? If set, e.g., wait 1s, otherwise magic number > > > 10? > > > > crashkernel=1G,cma,cma_sane_dma # no wait on transition > > But is no wait ok? I mean, any O_DIRECT with any device would at least take > a bit, no? > > Of course, there is a short time between the crash and actually triggerying > kdump.
This is something we can test for and if we need a short timeout in this case as well then it is just trivial to add it. I am much more concerned about those potentially unpredictable DMA transfers that could take too long and it is impossible to test for those and therefore we need to overshoot. > > crashkernel=1G,cma # wait on transition with e.g. 10s timeout > > In general, would work for me. > > -- > Cheers, > > David / dhildenb -- Michal Hocko SUSE Labs
