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grow the tmps (mortal) stack exponentially rather than linearly

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As with the value stack and the save stack, this gives us constant
amortized growth per element.

After this patch the profiler shows the "SvPV_shrink_to_cur(sv)"
and "sv = sv_2mortal(newSV(80))" calls in do_readline as the
hotspots for the io unheated test case, using 55% of the measured
time in total.

Fixes #21654
This commit is contained in:
Tony Cook 2023-11-23 14:22:03 +11:00
parent 7fbd97b4e8
commit fea90cfbe1
1 changed files with 6 additions and 2 deletions
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8
scope.c
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@ -246,8 +246,12 @@ Perl_tmps_grow_p(pTHX_ SSize_t ix)
{
SSize_t extend_to = ix;
#ifndef STRESS_REALLOC
if (ix - PL_tmps_max < 128)
extend_to += (PL_tmps_max < 512) ? 128 : 512;
SSize_t grow_size = PL_tmps_max < 512 ? 128 : PL_tmps_max / 2;
if (extend_to > SSize_t_MAX - grow_size - 1)
/* trigger memwrap message or fail allocation */
extend_to = SSize_t_MAX-1;
else
extend_to += grow_size;
#endif
Renew(PL_tmps_stack, extend_to + 1, SV*);
PL_tmps_max = extend_to + 1;