On 01/02/2017 12:02 PM, Jan Kara wrote: > Hi! > > On Wed 28-12-16 14:09:51, Michal Hocko wrote: >> I would like to propose the following for LSF/MM discussion. Both MM and >> FS people should be involved. >> >> The current way of the slab reclaim is rather suboptimal from 2 >> perspectives. >> >> 1) The slab allocator relies on shrinkers to release pages but shrinkers >> are object rather than page based. This means that the memory reclaim >> asks to free some pages, slab asks shrinkers to free some objects >> and the result might be that nothing really gets freed even though >> shrinkers do their jobs properly because some objects are still pinning >> the page. This is not a new problem and it has been discussed in the >> past. Dave Chinner has even suggested a solution [1] which sounds like >> the right approach. There was no follow up and I believe we should >> into implementing it. >> >> 2) The way we scale slab reclaim pressure depends on the regular LRU >> reclaim. There are workloads which do not general a lot of pages on LRUs >> while they still consume a lot of slab memory. We can end up even going >> OOM because the slab reclaim doesn't free up enough. I am not really >> sure how the proper solution should look like but either we need some >> way of slab consumption throttling or we need a more clever slab >> pressure estimation. >> >> [1] https://lkml.org/lkml/2010/2/8/329. > > I'm interested in this topic although I think it currently needs more > coding and experimenting than discussions... Yeah, some of the related stuff that was discussed at Kernel Summit [1] would be nice to have at least prototyped, i.e. the dentry cache separation and the slab helper for providing objects on the same page? [1] https://lwn.net/Articles/705758/ > > Honza > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
