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Stop providing branch prediction information

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The __builtin_expect() can be used to provide the compiler with branch
prediction information.  The Gcc manual says[1] on the subject:

    In general, you should prefer to use actual profile feedback for
    this (-fprofile-arcs), as programmers are notoriously bad at
    predicting how their programs actually perform.

Stop using __builtin_expect() and ISC_LIKELY() and ISC_UNLIKELY() macros
to provide the branch prediction information as the performance testing
shows that named performs better when the __builtin_expect() is not
being used.

1. https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-_005f_005fbuiltin_005fexpect
This commit is contained in:
Ondřej Surý
2021-10-14 10:33:24 +02:00
parent 80fedf9231
commit e603983ec9
25 changed files with 114 additions and 180 deletions
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4
lib/dns/message.c
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@@ -835,7 +835,7 @@ dns_message_findtype(const dns_name_t *name, dns_rdatatype_t type,
curr = ISC_LIST_PREV(curr, link))
{
if (curr->type == type && curr->covers == covers) {
if (ISC_UNLIKELY(rdataset != NULL)) {
if (rdataset != NULL) {
*rdataset = curr;
}
return (ISC_R_SUCCESS);
@@ -2450,7 +2450,7 @@ dns_message_findname(dns_message_t *msg, dns_section_t section,
/*
* And now look for the type.
*/
if (ISC_UNLIKELY(type == dns_rdatatype_any)) {
if (type == dns_rdatatype_any) {
return (ISC_R_SUCCESS);
}