On Sat, 22 Dec 2018 05:40:19 +0800 Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> wrote: > Swap readahead would read in a few pages regardless if the underlying > device is busy or not. It may incur long waiting time if the device is > congested, and it may also exacerbate the congestion. > > Use inode_read_congested() to check if the underlying device is busy or > not like what file page readahead does. Get inode from swap_info_struct. > Although we can add inode information in swap_address_space > (address_space->host), it may lead some unexpected side effect, i.e. > it may break mapping_cap_account_dirty(). Using inode from > swap_info_struct seems simple and good enough. > > Just does the check in vma_cluster_readahead() since > swap_vma_readahead() is just used for non-rotational device which > much less likely has congestion than traditional HDD. > > Although swap slots may be consecutive on swap partition, it still may be > fragmented on swap file. This check would help to reduce excessive stall > for such case. Some words about the observed effects of the patch would be more than appropriate!
