On Sat, Jul 9, 2022 at 8:45 AM Yafang Shao <laoar.shao@xxxxxxxxx> wrote: > > GFP_ATOMIC doesn't cooperate well with memcg pressure so far, especially > if we allocate too much GFP_ATOMIC memory. For example, when we set the > memcg limit to limit a non-preallocated bpf memory, the GFP_ATOMIC can > easily break the memcg limit by force charge. So it is very dangerous to > use GFP_ATOMIC in non-preallocated case. One way to make it safe is to > remove __GFP_HIGH from GFP_ATOMIC, IOW, use (__GFP_ATOMIC | > __GFP_KSWAPD_RECLAIM) instead, then it will be limited if we allocate > too much memory. There's a plan to completely remove __GFP_ATOMIC in the > mm side[1], so let's use GFP_NOWAIT instead. > > We introduced BPF_F_NO_PREALLOC is because full map pre-allocation is > too memory expensive for some cases. That means removing __GFP_HIGH > doesn't break the rule of BPF_F_NO_PREALLOC, but has the same goal with > it-avoiding issues caused by too much memory. So let's remove it. > > This fix can also apply to other run-time allocations, for example, the > allocation in lpm trie, local storage and devmap. So let fix it > consistently over the bpf code > > It also fixes a typo in the comment. > > [1]. https://lore.kernel.org/linux-mm/163712397076.13692.4727608274002939094@xxxxxxxxxxxxxxxxxxxxx/ > > Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> > Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> > Cc: NeilBrown <neilb@xxxxxxx> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
