On Sat 27-11-21 16:00:43, Andrew Morton wrote: > On Fri, 26 Nov 2021 11:48:46 +0100 Michal Hocko <mhocko@xxxxxxxx> wrote: > > > On Mon 22-11-21 16:32:31, Michal Hocko wrote: > > > From: Michal Hocko <mhocko@xxxxxxxx> > > > > > > Dave Chinner has mentioned that some of the xfs code would benefit from > > > kvmalloc support for __GFP_NOFAIL because they have allocations that > > > cannot fail and they do not fit into a single page. > > > > > > The large part of the vmalloc implementation already complies with the > > > given gfp flags so there is no work for those to be done. The area > > > and page table allocations are an exception to that. Implement a retry > > > loop for those. > > > > > > Add a short sleep before retrying. 1 jiffy is a completely random > > > timeout. Ideally the retry would wait for an explicit event - e.g. > > > a change to the vmalloc space change if the failure was caused by > > > the space fragmentation or depletion. But there are multiple different > > > reasons to retry and this could become much more complex. Keep the retry > > > simple for now and just sleep to prevent from hogging CPUs. > > > > > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > > > > Are there still any concerns around this patch or the approach in > > general? > > Well. Like GFP_NOFAIL, every use is a sin. But I don't think I've > ever seen a real-world report of anyone hitting GFP_NOFAIL's > theoretical issues. I am not sure what you mean here. If you are missing real GFP_NOFAIL use cases then some have been mentioned in the discussion > I assume there will be a v3? Currently I do not have any follow up changes on top of neither of the patch except for acks and review tags. I can repost with those if you prefer. -- Michal Hocko SUSE Labs
