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library: minimize the use of 'cleanup_stacks' routines

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Some parts of our newlib implementation are the result
of functions which have been propagated from module to
module. In particular, those 'cleanup_stacks' routines
are all similar & likely originated in the <pids> api.

In that interface there was a need to free dynamically
acquired memory before the result structure was reused
to satisfy subsequent 'get', 'select' or 'reap' calls.
This, in turn, led to a concept of 'dirty' stacks with
the need to call one of two 'cleanup_stack' functions.

None of the remaining interfaces deal with such memory
yet they each had their own 'cleanup_stack' functions.
Those functions were responsible for resetting each of
the result unions to zero, excluding any 'noop' items.

The bottom line is that for all interfaces, repetitive
calls would require iterating through the stack(s) two
separate times: once to 'cleanup' another to 'assign'.

With this commit we will reduce iterations to just the
'assign' routine. A reset to zero will be accomplished
in the 'extra' item set routine (which is the only one
actually requiring any reset). All other items will be
reinitialized automatically by a new current set value
or upon reallocation when an items compliment changes.

In the <pids> interface, any freeing of dynamic memory
could have been accomplished by adding that 'freefunc'
check to the 'assign' function. However, that requires
an Item_table test with every item. Instead, we'll now
satisfy such needs as the very first step in those set
functions responsible for dynamically acquired memory.

[ the <pids> api retains 2 'cleanup_stack' functions ]
[ to accommodate stack(s) 'reset' & to serve 'unref' ]

Lastly, all the 'itemize_stack' functions were tweaked
by eliminating an unnecessary initialization of result
unions. That objective was already accomplished by the
calloc() in a 'stacks_alloc' function or the remaining
'cleanup_stack' routine found in the <pids> interface.

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2019-05-22 00:00:00 -05:00
committed by Craig Small
parent 22a3bcbd6d
commit 40883a0b85
6 changed files with 33 additions and 221 deletions
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38
proc/vmstat.c
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@ -203,7 +203,6 @@ struct stacks_extent {
struct vmstat_info {
int refcount;
int vmstat_fd;
int dirty_stacks;
struct vmstat_hist hist;
int numitems;
enum vmstat_item *items;
@ -224,8 +223,8 @@ struct vmstat_info {
// delta assignment
#define HST_set(e,x) setDECL(e) { R->result.sl_int = ( H->new . x - H->old. x ); }
setDECL(noop) { (void)R; (void)H; }
setDECL(extra) { (void)R; (void)H; }
setDECL(noop) { (void)R; (void)H; }
setDECL(extra) { (void)H; R->result.ul_int = 0; }
REG_set(ALLOCSTALL_DMA, allocstall_dma)
REG_set(ALLOCSTALL_DMA32, allocstall_dma32)
@ -844,34 +843,6 @@ static inline void vmstat_assign_results (
} // end: vmstat_assign_results
static inline void vmstat_cleanup_stack (
struct vmstat_result *this)
{
for (;;) {
if (this->item >= VMSTAT_logical_end)
break;
if (this->item > VMSTAT_noop)
this->result.ul_int = 0;
++this;
}
} // end: vmstat_cleanup_stack
static inline void vmstat_cleanup_stacks_all (
struct vmstat_info *info)
{
struct stacks_extent *ext = info->extents;
int i;
while (ext) {
for (i = 0; ext->stacks[i]; i++)
vmstat_cleanup_stack(ext->stacks[i]->head);
ext = ext->next;
};
info->dirty_stacks = 0;
} // end: vmstat_cleanup_stacks_all
static void vmstat_extents_free_all (
struct vmstat_info *info)
{
@ -893,7 +864,6 @@ static inline struct vmstat_result *vmstat_itemize_stack (
for (i = 0; i < depth; i++) {
p->item = items[i];
p->result.ul_int = 0;
++p;
}
return p_sav;
@ -1369,13 +1339,9 @@ PROCPS_EXPORT struct vmstat_stack *procps_vmstat_select (
&& (!vmstat_stacks_alloc(info, 1)))
return NULL;
if (info->dirty_stacks)
vmstat_cleanup_stacks_all(info);
if (vmstat_read_failed(info))
return NULL;
vmstat_assign_results(info->extents->stacks[0], &info->hist);
info->dirty_stacks = 1;
return info->extents->stacks[0];
} // end: procps_vmstat_select