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. block/bio.c:464: gfp_mask &= ~__GFP_DIRECT_RECLAIM; drivers/vhost/net.c:668: pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) | drivers/net/ethernet/mellanox/mlx4/icm.c:184: mask &= ~__GFP_DIRECT_RECLAIM; fs/erofs/zdata.c:243: gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) | fs/fscache/page.c:138: gfp &= ~__GFP_DIRECT_RECLAIM; fs/fscache/cookie.c:187: INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_DIRECT_RECLAIM); fs/btrfs/disk-io.c:2928: INIT_RADIX_TREE(&fs_info->reada_tree, GFP_NOFS & ~__GFP_DIRECT_RECLAIM); fs/btrfs/volumes.c:6868: INIT_RADIX_TREE(&dev->reada_zones, GFP_NOFS & ~__GFP_DIRECT_RECLAIM); fs/btrfs/volumes.c:6869: INIT_RADIX_TREE(&dev->reada_extents, GFP_NOFS & ~__GFP_DIRECT_RECLAIM); kernel/cgroup/cgroup.c:325: ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM); mm/mempool.c:389: gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO); mm/hugetlb.c:2165: gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL); mm/mempolicy.c:2061: preferred_gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL); mm/memcontrol.c:5452: ret = try_charge(mc.to, GFP_KERNEL & ~__GFP_DIRECT_RECLAIM, count); net/core/sock.c:2623: pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) | net/core/skbuff.c:6084: page = alloc_pages((gfp_mask & ~__GFP_DIRECT_RECLAIM) | net/netlink/af_netlink.c:1302: (allocation & ~__GFP_DIRECT_RECLAIM) | net/netlink/af_netlink.c:2259: (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) | > > -- > Michal Hocko > SUSE Labs
