Re: FunctionCallN improvement.

Tom Lane wrote:
> Neil Conway <neilc(at)samurai(dot)com> writes:
> > I agree; I think the macro is a nice improvement to readability.
>
> But a dead loss for performance, since it does a MemSet *and* some other
> operations. What's worse, it changes a word-aligned MemSet into a
> non-aligned one, knocking out all the optimizations therein.

Thanks for your advice.
I change MemSet to for-loop in this macro.

I think FunctionCallInfoData is large to initialize it by using MemSet.
MemSet is very fast in most cases. However, when it only has to
initialize a part of large structure, it might be faster to initialize
the few members directly.

I made the test program to measure the effect of this macro.
The test program was:
---------------------------------------------------------------------------
#include "postgres.h"
#include "fmgr.h"
#include <stdio.h>

/*
* Initialize minimum fields of FunctionCallInfoData that must be
* initialized.
*/
#define InitFunctionCallInfoData(Fcinfo, Flinfo, Nargs) \
do { \
int i_; \
(Fcinfo)->flinfo = Flinfo; \
(Fcinfo)->context = NULL; \
(Fcinfo)->resultinfo = NULL; \
(Fcinfo)->isnull = false; \
(Fcinfo)->nargs = Nargs; \
for(i_ = 0; i_ < Nargs; i_++) (Fcinfo)->argnull[i_] = false; \
} while(0)

/*
* dummyFunc is to control excessive optimization.
* When this function is not called from loop, the initialization of
* FunctionCallInfoData might move outside of the loop by gcc.
*/
void dummyFunc(FunctionCallInfoData *fcinfo, int cnt)
{
fcinfo->arg[0] = Int32GetDatum(cnt);
}

void TestMemSet(int cnt, int nargs)
{
FunctionCallInfoData fcinfo;

printf("test MemSet: %d\n", cnt);

for(; cnt; cnt--) {
MemSet(&fcinfo, 0, sizeof(fcinfo));
dummyFunc(&fcinfo, cnt);
}
}

void TestMacro(int cnt, int nargs)
{
FunctionCallInfoData fcinfo;

printf("test Macro: %d\n", cnt);

for(; cnt; cnt--) {
InitFunctionCallInfoData(&fcinfo, NULL, nargs);
dummyFunc(&fcinfo, cnt);
}
}

int main(int argc, char **argv)
{
int test_cnt;
int nargs;

if(argc != 4) {
printf("usage: fmgrtest -memset|-macro test_cnt nargs\n");
return 1;
}
test_cnt = atoi(argv[2]);
nargs = atoi(argv[3]);

if(strcmp(argv[1], "-memset") == 0) TestMemSet(test_cnt, nargs);
if(strcmp(argv[1], "-macro") == 0) TestMacro(test_cnt, nargs);

return 0;
}
---------------------------------------------------------------------------

It was compiled like so:
gcc -O2 -o test_fmgr -I ${PGSRC}/src/include/ test_fmgr.c

Executed the test of MemSet:
time ./test_fmgr -memset 10000000 9

Executed the test of Macro that uses for loop:
time ./test_fmgr -macro 10000000 9

Results:
(1)linux Kernel 2.4.9 (Pentium III 800MHz, gcc-3.4.1)
MemSet real 0m1.486s, user 0m1.480s, sys 0m0.000s
Macro(nargs=9) real 0m0.606s, user 0m0.600s, sys 0m0.000s
Macro(nargs=3) real 0m0.375s, user 0m0.370s, sys 0m0.000s
Macro(nargs=2) real 0m0.298s, user 0m0.290s, sys 0m0.000s
(*)In the test of MemSet, nargs is not related.

(2)Solaris8 (Ultra SPARC III 750MHz, gcc-2.95.3)
MemSet real 2.0s, user 2.0s, sys 0.0s
Macro(nargs=9) real 0.7s, user 0.7s, sys 0.0s
Macro(nargs=3) real 0.3s, user 0.3s, sys 0.0s
Macro(nargs=2) real 0.2s, user 0.2s, sys 0.0s

The effect of this macro can be seen in the application that outputs
a lot of data such as psql and pg_dump. These applications enlarge
the load of FunctionCall3.

This is a result of pg_dump.
Environment: linux Kernel 2.4.9, Pentium III 800MHz,
PostgreSQL 8.0.1, gcc-3.4.1, compile option: -O2,
My database have about 400,000 tuples.
Results(time pg_dump > dump.sql):
Original code: real 0m5.369s, user 0m0.600s, sys 0m0.120s
Using this macro in fmgr.c: real 0m5.061s, user 0m0.550s, sys 0m0.120s

I think this macro is improvement to readability and performance.

regards,

---
A.Ogawa ( a_ogawa(at)hi-ho(dot)ne(dot)jp )