Hi Anna-
> On Jan 10, 2020, at 5:34 PM, schumaker.anna@xxxxxxxxx wrote:
>
> From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
>
> There are some workloads where READ_PLUS might end up hurting
> performance,
Can you say more about this? Have you seen workloads that are
hurt by READ_PLUS? Nothing jumps out at me from the tables in
the cover letter.
> so let's be nice to users and provide a way to disable this
> operation similar to how READDIR_PLUS can be disabled.
Does it make sense to hold off on a mount option until there
is evidence that there is no other way to work around such a
performance regression?
- Attempt to address the regression directly
- Improve the heuristics about when READ_PLUS is used
- Document that dropping back to vers=4.1 will disable it
Any experience with NFS/RDMA?
> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> ---
> fs/nfs/fs_context.c | 14 ++++++++++++++
> fs/nfs/nfs4client.c | 3 +++
> include/linux/nfs_fs_sb.h | 1 +
> 3 files changed, 18 insertions(+)
>
> diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
> index 0247dcb7b316..82ba07c7c1ce 100644
> --- a/fs/nfs/fs_context.c
> +++ b/fs/nfs/fs_context.c
> @@ -64,6 +64,7 @@ enum nfs_param {
> Opt_proto,
> Opt_rdirplus,
> Opt_rdma,
> + Opt_readplus,
> Opt_resvport,
> Opt_retrans,
> Opt_retry,
> @@ -120,6 +121,7 @@ static const struct fs_parameter_spec nfs_param_specs[] = {
> fsparam_string("proto", Opt_proto),
> fsparam_flag_no("rdirplus", Opt_rdirplus),
> fsparam_flag ("rdma", Opt_rdma),
> + fsparam_flag_no("readplus", Opt_readplus),
> fsparam_flag_no("resvport", Opt_resvport),
> fsparam_u32 ("retrans", Opt_retrans),
> fsparam_string("retry", Opt_retry),
> @@ -555,6 +557,12 @@ static int nfs_fs_context_parse_param(struct fs_context *fc,
> else
> ctx->options |= NFS_OPTION_MIGRATION;
> break;
> + case Opt_readplus:
> + if (result.negated)
> + ctx->options |= NFS_OPTION_NO_READ_PLUS;
> + else
> + ctx->options &= ~NFS_OPTION_NO_READ_PLUS;
> + break;
>
> /*
> * options that take numeric values
> @@ -1176,6 +1184,10 @@ static int nfs_fs_context_validate(struct fs_context *fc)
> (ctx->version != 4 || ctx->minorversion != 0))
> goto out_migration_misuse;
>
> + if (ctx->options & NFS_OPTION_NO_READ_PLUS &&
> + (ctx->version != 4 || ctx->minorversion < 2))
> + goto out_noreadplus_misuse;
> +
> /* Verify that any proto=/mountproto= options match the address
> * families in the addr=/mountaddr= options.
> */
> @@ -1254,6 +1266,8 @@ static int nfs_fs_context_validate(struct fs_context *fc)
> ctx->version, ctx->minorversion);
> out_migration_misuse:
> return nfs_invalf(fc, "NFS: 'Migration' not supported for this NFS version");
> +out_noreadplus_misuse:
> + return nfs_invalf(fc, "NFS: 'noreadplus' not supported for this NFS version\n");
> out_version_unavailable:
> nfs_errorf(fc, "NFS: Version unavailable");
> return ret;
> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
> index 0cd767e5c977..868dc3c36ba1 100644
> --- a/fs/nfs/nfs4client.c
> +++ b/fs/nfs/nfs4client.c
> @@ -1016,6 +1016,9 @@ static int nfs4_server_common_setup(struct nfs_server *server,
> server->caps |= server->nfs_client->cl_mvops->init_caps;
> if (server->flags & NFS_MOUNT_NORDIRPLUS)
> server->caps &= ~NFS_CAP_READDIRPLUS;
> + if (server->options & NFS_OPTION_NO_READ_PLUS)
> + server->caps &= ~NFS_CAP_READ_PLUS;
> +
> /*
> * Don't use NFS uid/gid mapping if we're using AUTH_SYS or lower
> * authentication.
> diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
> index 11248c5a7b24..360e70c7bbb6 100644
> --- a/include/linux/nfs_fs_sb.h
> +++ b/include/linux/nfs_fs_sb.h
> @@ -172,6 +172,7 @@ struct nfs_server {
> unsigned int clone_blksize; /* granularity of a CLONE operation */
> #define NFS_OPTION_FSCACHE 0x00000001 /* - local caching enabled */
> #define NFS_OPTION_MIGRATION 0x00000002 /* - NFSv4 migration enabled */
> +#define NFS_OPTION_NO_READ_PLUS 0x00000004 /* - NFSv4.2 READ_PLUS enabled */
>
> struct nfs_fsid fsid;
> __u64 maxfilesize; /* maximum file size */
> --
> 2.24.1
>
--
Chuck Lever
