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top: eliminate yet more gcc subscript resolution bloat

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This patch is inspired by the 'minimize numa overhead'
patch. It trades the use of subscripts for pointers to
avoid gcc repeated subscript offset calculation bloat.

Now, throughout the cpus_refresh function, a subscript
will be resolved just once & this will (dramatically?)
reduce the path-length taken for each and every frame!

For example, a non-optimized compilation could produce
400+ fewer machine instructions through pointer usage.

[ ok, optimized compiles only save 18+ instructions! ]

Lastly, any residual 'symmetry only' crap is now gone!

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2013-11-09 00:00:00 -06:00 committed by Craig Small
parent f12c0d5c6e
commit 89c2f28e39
1 changed files with 33 additions and 32 deletions
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65
top/top.c
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@ -2298,6 +2298,7 @@ static CPU_t *cpus_refresh (CPU_t *cpus) {
static FILE *fp = NULL;
static int siz, sav_slot = -1;
static char *buf;
CPU_t *sum_ptr; // avoid gcc subscript bloat
int i, num, tot_read;
#ifndef NUMA_DISABLE
int node;
@ -2342,76 +2343,76 @@ static CPU_t *cpus_refresh (CPU_t *cpus) {
#undef buffGRW
// remember from last time around
memcpy(&cpus[sumSLOT].sav, &cpus[sumSLOT].cur, sizeof(CT_t));
sum_ptr = &cpus[sumSLOT];
memcpy(&sum_ptr->sav, &sum_ptr->cur, sizeof(CT_t));
// then value the last slot with the cpu summary line
if (4 > sscanf(bp, "cpu %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu"
, &cpus[sumSLOT].cur.u, &cpus[sumSLOT].cur.n, &cpus[sumSLOT].cur.s
, &cpus[sumSLOT].cur.i, &cpus[sumSLOT].cur.w, &cpus[sumSLOT].cur.x
, &cpus[sumSLOT].cur.y, &cpus[sumSLOT].cur.z))
, &sum_ptr->cur.u, &sum_ptr->cur.n, &sum_ptr->cur.s
, &sum_ptr->cur.i, &sum_ptr->cur.w, &sum_ptr->cur.x
, &sum_ptr->cur.y, &sum_ptr->cur.z))
error_exit(N_txt(FAIL_statget_txt));
#ifndef CPU_ZEROTICS
cpus[sumSLOT].cur.tot = cpus[sumSLOT].cur.u + cpus[sumSLOT].cur.s
+ cpus[sumSLOT].cur.n + cpus[sumSLOT].cur.i + cpus[sumSLOT].cur.w
+ cpus[sumSLOT].cur.x + cpus[sumSLOT].cur.y + cpus[sumSLOT].cur.z;
sum_ptr->cur.tot = sum_ptr->cur.u + sum_ptr->cur.s
+ sum_ptr->cur.n + sum_ptr->cur.i + sum_ptr->cur.w
+ sum_ptr->cur.x + sum_ptr->cur.y + sum_ptr->cur.z;
/* if a cpu has registered substantially fewer tics than those expected,
we'll force it to be treated as 'idle' so as not to present misleading
percentages. */
cpus[sumSLOT].edge =
((cpus[sumSLOT].cur.tot - cpus[sumSLOT].sav.tot) / smp_num_cpus) / (100 / TICS_EDGE);
sum_ptr->edge =
((sum_ptr->cur.tot - sum_ptr->sav.tot) / smp_num_cpus) / (100 / TICS_EDGE);
#endif
#ifndef NUMA_DISABLE
// forget all of the prior node statistics (maybe)
if (CHKw(Curwin, View_CPUNOD))
memset(&cpus[sumSLOT + 1], 0, Numa_node_tot * sizeof(CPU_t));
memset(sum_ptr + 1, 0, Numa_node_tot * sizeof(CPU_t));
#endif
// now value each separate cpu's tics...
for (i = 0; i < sumSLOT; i++) {
CPU_t *cpu_ptr = &cpus[i]; // avoid gcc subscript bloat
#ifdef PRETEND8CPUS
bp = buf;
#endif
bp = 1 + strchr(bp, '\n');
// remember from last time around
memcpy(&cpus[i].sav, &cpus[i].cur, sizeof(CT_t));
if (4 > sscanf(bp, "cpu%d %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu", &cpus[i].id
, &cpus[i].cur.u, &cpus[i].cur.n, &cpus[i].cur.s
, &cpus[i].cur.i, &cpus[i].cur.w, &cpus[i].cur.x
, &cpus[i].cur.y, &cpus[i].cur.z)) {
memmove(&cpus[i], &cpus[sumSLOT], sizeof(CPU_t));
memcpy(&cpu_ptr->sav, &cpu_ptr->cur, sizeof(CT_t));
if (4 > sscanf(bp, "cpu%d %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu", &cpu_ptr->id
, &cpu_ptr->cur.u, &cpu_ptr->cur.n, &cpu_ptr->cur.s
, &cpu_ptr->cur.i, &cpu_ptr->cur.w, &cpu_ptr->cur.x
, &cpu_ptr->cur.y, &cpu_ptr->cur.z)) {
memmove(cpu_ptr, sum_ptr, sizeof(CPU_t));
break; // tolerate cpus taken offline
}
#ifndef CPU_ZEROTICS
cpus[i].edge = cpus[sumSLOT].edge;
// this is for symmetry only, it's not currently required
cpus[i].cur.tot = cpus[sumSLOT].cur.tot;
cpu_ptr->edge = sum_ptr->edge;
#endif
#ifdef PRETEND8CPUS
cpus[i].id = i;
cpu_ptr->id = i;
#endif
#ifndef NUMA_DISABLE
/* henceforth, with just a little more arithmetic we can avoid
maintaining *any* node stats unless they're actually needed */
if (CHKw(Curwin, View_CPUNOD)
&& Numa_node_tot
&& -1 < (node = Numa_node_of_cpu(cpus[i].id))) {
&& -1 < (node = Numa_node_of_cpu(cpu_ptr->id))) {
// use our own pointer to avoid gcc subscript bloat
CPU_t *nod_ptr = &cpus[sumSLOT + 1 + node];
nod_ptr->cur.u += cpus[i].cur.u; nod_ptr->sav.u += cpus[i].sav.u;
nod_ptr->cur.n += cpus[i].cur.n; nod_ptr->sav.n += cpus[i].sav.n;
nod_ptr->cur.s += cpus[i].cur.s; nod_ptr->sav.s += cpus[i].sav.s;
nod_ptr->cur.i += cpus[i].cur.i; nod_ptr->sav.i += cpus[i].sav.i;
nod_ptr->cur.w += cpus[i].cur.w; nod_ptr->sav.w += cpus[i].sav.w;
nod_ptr->cur.x += cpus[i].cur.x; nod_ptr->sav.x += cpus[i].sav.x;
nod_ptr->cur.y += cpus[i].cur.y; nod_ptr->sav.y += cpus[i].sav.y;
nod_ptr->cur.z += cpus[i].cur.z; nod_ptr->sav.z += cpus[i].sav.z;
CPU_t *nod_ptr = sum_ptr + 1 + node;
nod_ptr->cur.u += cpu_ptr->cur.u; nod_ptr->sav.u += cpu_ptr->sav.u;
nod_ptr->cur.n += cpu_ptr->cur.n; nod_ptr->sav.n += cpu_ptr->sav.n;
nod_ptr->cur.s += cpu_ptr->cur.s; nod_ptr->sav.s += cpu_ptr->sav.s;
nod_ptr->cur.i += cpu_ptr->cur.i; nod_ptr->sav.i += cpu_ptr->sav.i;
nod_ptr->cur.w += cpu_ptr->cur.w; nod_ptr->sav.w += cpu_ptr->sav.w;
nod_ptr->cur.x += cpu_ptr->cur.x; nod_ptr->sav.x += cpu_ptr->sav.x;
nod_ptr->cur.y += cpu_ptr->cur.y; nod_ptr->sav.y += cpu_ptr->sav.y;
nod_ptr->cur.z += cpu_ptr->cur.z; nod_ptr->sav.z += cpu_ptr->sav.z;
#ifndef CPU_ZEROTICS
/* yep, we re-value this repeatedly for each cpu encountered, but we
can then avoid a prior loop to selectively initialize each node */
nod_ptr->edge = cpus[sumSLOT].edge;
nod_ptr->edge = sum_ptr->edge;
#endif
cpus[i].node = node;
cpu_ptr->node = node;
}
#endif
} // end: for each cpu