On Wed 27-10-21 20:05:30, Zhaoyang Huang wrote: > On Wed, Oct 27, 2021 at 7:52 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Wed 27-10-21 17:19:56, Zhaoyang Huang wrote: > > > On Wed, Oct 27, 2021 at 4:26 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > > > On Wed 27-10-21 15:46:19, Zhaoyang Huang wrote: > > > > > On Wed, Oct 27, 2021 at 3:20 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > > > > > > > On Wed 27-10-21 15:01:50, Huangzhaoyang wrote: > > > > > > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > > > > > > > > > > > > For the kswapd only reclaiming, there is no chance to try again on > > > > > > > this group while direct reclaim has. fix it by judging gfp flag. > > > > > > > > > > > > There is no problem description (same as in your last submissions. Have > > > > > > you looked at the patch submission documentation as recommended > > > > > > previously?). > > > > > > > > > > > > Also this patch doesn't make any sense. Both direct reclaim and kswapd > > > > > > use a gfp mask which contains __GFP_DIRECT_RECLAIM (see balance_pgdat > > > > > > for the kswapd part).. > > > > > ok, but how does the reclaiming try with memcg's min protection on the > > > > > alloc without __GFP_DIRECT_RECLAIM? > > > > > > > > I do not follow. There is no need to protect memcg if the allocation > > > > request doesn't have __GFP_DIRECT_RECLAIM because that would fail the > > > > charge if a hard limit is reached, see try_charge_memcg and > > > > gfpflags_allow_blocking check. > > > > > > > > Background reclaim, on the other hand never breaches reclaim protection. > > > > > > > > What is the actual problem you want to solve? > > > Imagine there is an allocation with gfp_mask & ~GFP_DIRECT_RECLAIM and > > > all processes are under cgroups. Kswapd is the only hope here which > > > however has a low efficiency of get_scan_count. I would like to have > > > kswapd work as direct reclaim in 2nd round which will have > > > protection=memory.min. > > > > Do you have an example where this would be a practical problem? Atomic > > allocations should be rather rare. > Please find below for the search result of '~__GFP_DIRECT_RECLAIM' > which shows some drivers and net prefer to behave like that. > Furthermore, the allocations are always together with high order. And what is the _practical_ problem you are seeing or trying to solve? -- Michal Hocko SUSE Labs
