Before this major redesign, the slabs interface likely
was our messiest 2nd generation attempt at opaqueness.
Beyond the standard 'new', 'ref' & 'unref', there were
a total of 12 exported functions. Now, there are four.
The 1st step was to remove several of those functions.
These were quick to go since they were not used (yet):
. procps_slabnode_count
. procps_slabnode_getname
. procps_slabnode_getstack
Then, the following were internalized so users needn't
be burdened with implementation details in the future:
. procps_slabinfo_read (renamed: read_slabinfo_failed)
. procps_slabnode_stacks_alloc (renamed: stacks_alloc)
Still others evolved into the minimal interface we had
strived for in the other upgraded 3rd generation APIs:
. procps_slabnode_get -----------> procps_slabinfo_get
. separate stack_alloc/fill --> procps_slabinfo_select
. separate stacks_alloc/fill ---> procps_slabinfo_reap
. procps_slabnode_stacks_sort --> procps_slabinfo_sort
------------------------------------------------------
Beyond those reductions, the major modifications were:
. This API tries to be as forgiving as possible and as
such won't throw errors when a caller request makes no
sense. For example, if a 'get' or 'select' requested a
SLABNODE item (with no current means to id that node),
results will be zero. By the same token, should 'reap'
include a global SLABS item (meaning those values will
be duplicated in *every* node stack) it'll be allowed.
. If the above behavior is undesired, a new #define of
ENFORCE_LOGICAL can be used to restrict certain items.
. Permission problems will now be caught at 'new' time
thanks to a priming 'read' call. That read also serves
to make DELTA values potentially useful at 1st access.
. Separate slab/slabnode enumerators were consolidated
into one, simplifying validation & the results struct.
. Several internal parameter checks were relaxed since
they were already checked by the caller. Besides if we
cannot trust our own code we might as well hang it up.
. That sort provision was made more efficient and will
offer the ascending choice, in addition to descending.
------------------------------------------------------
Lastly, some additional thoughts regarding the future:
. It would not be difficult to expand 'select' to also
accept a nodeid, or to clone it as 'select_node'. And,
should the same be extended to 'get', a results struct
could be returned instead of signed long accommodating
the extra data type(s) like a node name (string data).
. The 'get' function is not currently affected by that
define ENFORCE_LOGICAL. However, at some future point
perhaps -EINVAL would be more appropriate than a zero.
Signed-off-by: Jim Warner <james.warner@comcast.net>
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