On Thu, Mar 23, 2023 at 8:01 AM <xiubli@xxxxxxxxxx> wrote: > > From: Xiubo Li <xiubli@xxxxxxxxxx> > > Blindly expanding the readahead windows will cause unneccessary > pagecache thrashing and also will introdue the network workload. > We should disable expanding the windows if the readahead is disabled > and also shouldn't expand the windows too much. > > Expanding forward firstly instead of expanding backward for possible > sequential reads. > > URL: https://www.spinics.net/lists/ceph-users/msg76183.html > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> > --- > fs/ceph/addr.c | 23 +++++++++++++++++------ > 1 file changed, 17 insertions(+), 6 deletions(-) > > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c > index ca4dc6450887..01d997f6c66c 100644 > --- a/fs/ceph/addr.c > +++ b/fs/ceph/addr.c > @@ -188,16 +188,27 @@ static void ceph_netfs_expand_readahead(struct netfs_io_request *rreq) > struct inode *inode = rreq->inode; > struct ceph_inode_info *ci = ceph_inode(inode); > struct ceph_file_layout *lo = &ci->i_layout; > + unsigned long max_pages = inode->i_sb->s_bdi->ra_pages; > + unsigned long max_len = max_pages << PAGE_SHIFT; > + unsigned long len; > u32 blockoff; > u64 blockno; > > - /* Expand the start downward */ > - blockno = div_u64_rem(rreq->start, lo->stripe_unit, &blockoff); > - rreq->start = blockno * lo->stripe_unit; > - rreq->len += blockoff; > + /* Readahead is disabled */ > + if (!max_pages) > + return; > + > + /* Expand the length forward by rounding up it to the next block */ > + len = roundup(rreq->len, lo->stripe_unit); > + if (len <= max_len) > + rreq->len = len; Hi Xiubo, This change makes it possible for the request to be expanded into the next block (i.e. it's not rounded _up_ to the next block as the comment says) because rreq->len is no longer guaranteed to be based off of the start of the block here. Previously that was ensured by the preceding downward expansion. Thanks, Ilya
