Hi Jeff,
The issue is more of repetition. On an 8-socket system, should a user really
be expected to type 'ndctl create-namespace' eight times vs. running 'ndctl
create-namespace --region=all' once? SAP HANA is an example app the requires
one namespace per region. Scripting is a viable solution, but that requires
somebody to write the script and do all the error checking & handling. Each
OEM/ISV/SysAdmin would have their own script. Pushing the logic to ndctl seems
to be a reasonable approach and let the user handle any errors returned by
ndctl.
The ndctl-man-page implies the 'ndctl create-namespace --region=all' feature
exists today:
-r, --region=
A regionX device name, or a region id number. The keyword all can be
specified to carry out the operation on every region in the system, optionally
filtered by bus id (see --bus= option).
-Steve
-----Original Message-----
From: Jeff Moyer [mailto:jmo...@redhat.com]
Sent: Wednesday, August 28, 2019 2:13 PM
To: Verma, Vishal L <vishal.l.ve...@intel.com>
Cc: linux-nvdimm@lists.01.org; Scargall, Steve <steve.scarg...@intel.com>;
Williams, Dan J <dan.j.willi...@intel.com>
Subject: Re: [ndctl RFC PATCH] ndctl/namespace: create namespaces greedily
Vishal Verma <vishal.l.ve...@intel.com> writes:
> When a --region=all option is supplied to ndctl-create-namespace, it
> happily ignores it, since create-namespace has historically only
> created one namespace per invocation.
>
> This can be cumbersome, so change create-namespace to create
> namespaces greedily. When --region=all is specified, or if a --region
> option is absent (same as 'all' from a filtering standpoint), create
> namespaces on all regions.
Cumbersome? Like, in the same way partitioning a disk is cumbersome? I don't
understand what the problem is, I guess. If you want N namespaces of the same
type/size/align, then script it. Why does there have to be a command for that?
I definitely think that changing the behavior of create-namespace is a
non-starter.
Cheers,
Jeff
>
> Note that this does has two important implications:
>
> 1. The user-facing behavior of create-namespace changes in a
> potentially surprising way. It may be undesirable for an unadorned
> 'ndctl create-namespace' command to suddenly start creating lots of
> namespaces.
>
> 2. Error handling becomes a bit inconsistent. As with all commands
> accepting an 'all' option, error reporting becomes a bit tenuous. With
> this change, we will continue to create namespaces so long as we don't
> hit an error, but if we do, we bail and exit. Because of the special
> ENOSPC detection and handling around this, it can be easy to construct
> a scenario where en existing namespace on the last region in the scan
> list happens to report an error exit, but if the existing namespace
> was in a region at the start of the scan list, it gets passed over as
> a "just try the next region"
>
> RFC comment: Maybe the solution is to keep the create-namespace
> semantics unchanged, and introduce a new command - 'create-namespaces'
> or 'create-names-ace-greedy' with the new behavior. I'm not sure if
> users will care deeply about either of the two points above, hence
> sending this as an RFC.
>
> Link: https://github.com/pmem/ndctl/issues/106
> Reported-by: Steve Scargal <steve.scarg...@intel.com>
> Cc: Jeff Moyer <jmo...@redhat.com>
> Cc: Dan Williams <dan.j.willi...@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.ve...@intel.com>
> ---
> ndctl/namespace.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/ndctl/namespace.c b/ndctl/namespace.c index
> af20a42..856ad82 100644
> --- a/ndctl/namespace.c
> +++ b/ndctl/namespace.c
> @@ -1365,9 +1365,12 @@ static int do_xaction_namespace(const char *namespace,
> rc = namespace_create(region);
> if (rc == -EAGAIN)
> continue;
> - if (rc == 0)
> - *processed = 1;
> - return rc;
> + if (rc == 0) {
> + (*processed)++;
> + continue;
> + } else {
> + return rc;
> + }
> }
> ndctl_namespace_foreach_safe(region, ndns, _n) {
> ndns_name = ndctl_namespace_get_devname(ndns);
> @@ -1487,6 +1490,8 @@ int cmd_create_namespace(int argc, const char **argv,
> struct ndctl_ctx *ctx)
> rc = do_xaction_namespace(NULL, ACTION_CREATE, ctx, &created);
> }
>
> + fprintf(stderr, "created %d namespace%s\n", created,
> + created == 1 ? "" : "s");
> if (rc < 0 || (!namespace && created < 1)) {
> fprintf(stderr, "failed to %s namespace: %s\n", namespace
> ? "reconfigure" : "create", strerror(-rc));
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