On 12/21/18 1:40 PM, Yang Shi 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. > > Cc: Huang Ying <[email protected]> > Cc: Tim Chen <[email protected]> > Cc: Minchan Kim <[email protected]> > Signed-off-by: Yang Shi <[email protected]> > --- > v3: Move inode deference under swap device type check per Tim Chen > v2: Check the swap device type per Tim Chen > > mm/swap_state.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index fd2f21e..78d500e 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -538,11 +538,18 @@ struct page *swap_cluster_readahead(swp_entry_t entry, > gfp_t gfp_mask, > bool do_poll = true, page_allocated; > struct vm_area_struct *vma = vmf->vma; > unsigned long addr = vmf->address; > + struct inode *inode = NULL; > > mask = swapin_nr_pages(offset) - 1; > if (!mask) > goto skip; > > + if (si->flags & (SWP_BLKDEV | SWP_FS)) { > + inode = si->swap_file->f_mapping->host; > + if (inode_read_congested(inode)) > + goto skip; > + } > + > do_poll = false; > /* Read a page_cluster sized and aligned cluster around offset. */ > start_offset = offset & ~mask; >
Acked-by: Tim Chen <[email protected]>
