On Mon, Jul 11, 2022 at 12:19 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > 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> Applied to bpf-next.
