On Thu, Jul 7, 2022 at 11:44 PM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Thu, Jul 7, 2022 at 3:28 AM Yafang Shao <laoar.shao@xxxxxxxxx> wrote: > > > > On Thu, Jul 7, 2022 at 8:07 AM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > > > On Wed, Jul 06, 2022 at 03:58:47PM +0000, Yafang Shao 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. > > > > > > Please use GFP_NOWAIT instead of (__GFP_ATOMIC | __GFP_KSWAPD_RECLAIM). > > > There is already a plan to completely remove __GFP_ATOMIC and mm-tree > > > already have a patch for that. > > > > > > > After reading the discussion[1], it looks good to me to use GFP_NOWAIT > > instead. I will update it. > > Should we use GFP_ATOMIC | __GFP_NOMEMALLOC instead > to align with its usage in the networking stack? GFP_ATOMIC | __GFP_NOMEMALLOC will continue to break the memcg limit, so we have to modify the try_charge_memcg() code to make sure __GFP_NOMEMALLOC takes precedence over the __GFP_HIGH flag, IOW, if both of them are set we won't allow it to break memcg limit. That will need more verification. -- Regards Yafang
