Makes sense to me.--b.
On Fri, Jan 22, 2021 at 03:21:10PM -0500, Chuck Lever wrote:
> During NFSv2 and NFSv3 READDIR/PLUS operations, NFSD advances
> rq_next_page to the full size of the client-requested buffer, then
> releases all those pages at the end of the request. The next request
> to use that nfsd thread has to refill the pages.
>
> NFSD does this even when the dirlist in the reply is small. With
> NFSv3 clients that send READDIR operations with large buffer sizes,
> that can be 256 put_page/alloc_page pairs per READDIR request, even
> though those pages often remain unused.
>
> We can save some work by not releasing dirlist buffer pages that
> were not used to form the READDIR Reply. I've left the NFSv2 code
> alone since there are never more than three pages involved in an
> NFSv2 READDIR operation.
>
> Eventually we should nail down why these pages need to be released
> at all in order to avoid allocating and releasing pages
> unnecessarily.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> fs/nfsd/nfs3proc.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
> index 8675851199f8..569bfff314f0 100644
> --- a/fs/nfsd/nfs3proc.c
> +++ b/fs/nfsd/nfs3proc.c
> @@ -492,6 +492,7 @@ nfsd3_proc_readdir(struct svc_rqst *rqstp)
> }
> count += PAGE_SIZE;
> }
> + rqstp->rq_next_page = p;
> resp->count = count >> 2;
> if (resp->offset) {
> if (unlikely(resp->offset1)) {
> @@ -557,6 +558,7 @@ nfsd3_proc_readdirplus(struct svc_rqst *rqstp)
> }
> count += PAGE_SIZE;
> }
> + rqstp->rq_next_page = p;
> resp->count = count >> 2;
> if (resp->offset) {
> if (unlikely(resp->offset1)) {
>
