在 2020/4/15 下午9:42, Alex Shi 写道: > Hi Johannes, > > Thanks a lot for point out! > > Charging in __read_swap_cache_async would ask for 3 layers function arguments > pass, that would be a bit ugly. Compare to this, could we move out the > lru_cache add after commit_charge, like ksm copied pages? > > That give a bit extra non lru list time, but the page just only be used only > after add_anon_rmap setting. Could it cause troubles? Hi Johannes & Andrew, Doing lru_cache_add_anon during swapin_readahead can give a very short timing for possible page reclaiming for these few pages. If we delay these few pages lru adding till after the vm_fault target page get memcg charging(mem_cgroup_commit_charge) and activate, we could skip the mem_cgroup_try_charge/commit_charge/cancel_charge process in __read_swap_cache_async(). But the cost is maximum SWAP_RA_ORDER_CEILING number pages on each cpu miss page reclaiming in a short time. On the other hand, save the target vm_fault page from reclaiming before activate it during that time. Judging the lose and gain, and the example of shmem/ksm copied pages, I believe it's fine to delay lru list adding till activate the target swapin page. Any comments are appreciated! Thanks Alex > > I tried to track down the reason of lru_cache_add here, but no explanation > till first git kernel commit. > > Thanks > Alex >
