On Wed 12-02-25 11:30:08, Tejun Heo wrote: > Hello, > > On Wed, Feb 12, 2025 at 09:53:20PM +0100, Michal Hocko wrote: > ... > > > Hmm... you'd a better judge on whether that'd be okay or not but it does > > > bother me that we might be increasing the chance of allocation failures for > > > GFP_KERNEL users at least under memory pressure. > > > > Nope, this will not change the allocation failure mode. Reclaim > > constrains do not change the failure mode they just change how much the > > allocation might struggle to reclaim to succeed. > > > > My undocumented assumption (another dept on my end) is that pcp > > allocations are no hot paths. So the worst case is that GFP_KERNEL > > pcp_allocation could have been satisfied _easier_ (i.e. faster) because > > it could have reclaimed fs/io caches and now it needs to rely on kswapd > > to do that on memory tight situations. On the other hand we have a > > situation when NOIO/FS allocations fail prematurely so there is > > certainly some pros and cons. > > I'm having a hard time following. Are you saying that it won't increase the > likelihood of allocation failures even under memory pressure but that it > might just make allocations take longer to succeed? yes, this is like any other NOFS/NOIO allocation non-costly (<=PAGE_ALLOC_COSTLY_ORDER) which effectively never fail. -- Michal Hocko SUSE Labs
