I need to rerun the perf numbers - I may have gotten some of them incorrectly.
On Sat, Apr 24, 2021 at 2:27 PM Steve French <smfrench@xxxxxxxxx> wrote:
>
> In some cases readahead of more than the read size can help
> (to allow parallel i/o of read ahead which can improve performance).
>
> Using the buildbot test systems, this resulted in an average improvement
> of 14% to the Windows server test target for the first 12 tests I
> tried (no multichannel)
> changing to 12MB rasize (read ahead size). Similarly increasing the
> rasize to 12MB to Azure (this time with multichannel, 4 channels)
> improved performance 37%
>
> Note that Ceph had already introduced a mount parameter "rasize" to
> allow controlling this. Add mount parameter "rasize" to cifs.ko to
> allow control of read ahead (rasize defaults to 4MB which is typically
> what it used to default to to the many servers whose rsize was that).
>
> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
> ---
> fs/cifs/cifsfs.c | 1 +
> fs/cifs/fs_context.c | 25 ++++++++++++++++++++++++-
> fs/cifs/fs_context.h | 2 ++
> 3 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 39f4889a036b..a1217682da1f 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -649,6 +649,7 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
> seq_printf(s, ",rsize=%u", cifs_sb->ctx->rsize);
> seq_printf(s, ",wsize=%u", cifs_sb->ctx->wsize);
> seq_printf(s, ",bsize=%u", cifs_sb->ctx->bsize);
> + seq_printf(s, ",rasize=%u", cifs_sb->ctx->rasize);
> if (tcon->ses->server->min_offload)
> seq_printf(s, ",esize=%u", tcon->ses->server->min_offload);
> seq_printf(s, ",echo_interval=%lu",
> diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
> index 74758e954035..5ce1f7b854e7 100644
> --- a/fs/cifs/fs_context.c
> +++ b/fs/cifs/fs_context.c
> @@ -137,6 +137,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
> fsparam_u32("min_enc_offload", Opt_min_enc_offload),
> fsparam_u32("esize", Opt_min_enc_offload),
> fsparam_u32("bsize", Opt_blocksize),
> + fsparam_u32("rasize", Opt_rasize),
> fsparam_u32("rsize", Opt_rsize),
> fsparam_u32("wsize", Opt_wsize),
> fsparam_u32("actimeo", Opt_actimeo),
> @@ -941,6 +942,26 @@ static int smb3_fs_context_parse_param(struct
> fs_context *fc,
> ctx->bsize = result.uint_32;
> ctx->got_bsize = true;
> break;
> + case Opt_rasize:
> + /*
> + * readahead size realistically should never need to be
> + * less than 1M (CIFS_DEFAULT_IOSIZE) or greater than 32M
> + * (perhaps an exception should be considered in the
> + * for the case of a large number of channels
> + * when multichannel is negotiated) since that would lead
> + * to plenty of parallel I/O in flight to the server.
> + * Note that smaller read ahead sizes would
> + * hurt performance of common tools like cp and scp
> + * which often trigger sequential i/o with read ahead
> + */
> + if ((result.uint_32 > (8 * SMB3_DEFAULT_IOSIZE)) ||
> + (result.uint_32 < CIFS_DEFAULT_IOSIZE)) {
> + cifs_errorf(fc, "%s: Invalid rasize %d vs. %d\n",
> + __func__, result.uint_32, SMB3_DEFAULT_IOSIZE);
> + goto cifs_parse_mount_err;
> + }
> + ctx->rasize = result.uint_32;
> + break;
> case Opt_rsize:
> ctx->rsize = result.uint_32;
> ctx->got_rsize = true;
> @@ -1377,7 +1398,9 @@ int smb3_init_fs_context(struct fs_context *fc)
> ctx->cred_uid = current_uid();
> ctx->linux_uid = current_uid();
> ctx->linux_gid = current_gid();
> - ctx->bsize = 1024 * 1024; /* can improve cp performance significantly */
> + /* By default 4MB read ahead size, 1MB block size */
> + ctx->bsize = CIFS_DEFAULT_IOSIZE; /* can improve cp performance
> significantly */
> + ctx->rasize = SMB3_DEFAULT_IOSIZE; /* can improve sequential read ahead */
>
> /*
> * default to SFM style remapping of seven reserved characters
> diff --git a/fs/cifs/fs_context.h b/fs/cifs/fs_context.h
> index 56d7a75e2390..2a71c8e411ac 100644
> --- a/fs/cifs/fs_context.h
> +++ b/fs/cifs/fs_context.h
> @@ -120,6 +120,7 @@ enum cifs_param {
> Opt_dirmode,
> Opt_min_enc_offload,
> Opt_blocksize,
> + Opt_rasize,
> Opt_rsize,
> Opt_wsize,
> Opt_actimeo,
> @@ -235,6 +236,7 @@ struct smb3_fs_context {
> /* reuse existing guid for multichannel */
> u8 client_guid[SMB2_CLIENT_GUID_SIZE];
> unsigned int bsize;
> + unsigned int rasize;
> unsigned int rsize;
> unsigned int wsize;
> unsigned int min_offload;
>
> --
> Thanks,
>
> Steve
--
Thanks,
Steve
