postgrespro.git / summary / log / commit / refs

commit    1fbb6c93df30801f83c6804ab7befde3cdefe677
Author:   Jeff Davis <jdavis@postgresql.org>
Date:     Sun Jun 07 16:14:24 2020 +0000

    Fix platform-specific performance regression in logtape.c.
    
    Commit 24d85952 made a change that indirectly caused a performance
    regression by triggering a change in the way GCC optimizes memcpy() on
    some platforms.
    
    The behavior seemed to contradict a GCC document, so I filed a report:
    
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95556
    
    This patch implements a narrow workaround which eliminates the
    regression I observed. The workaround is benign enough that it seems
    unlikely to cause a different regression on another platform.
    
    Discussion: https://postgr.es/m/99b2eab335c1592c925d8143979c8e9e81e1575f.camel@j-davis.com


 src/backend/utils/sort/logtape.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backend/utils/sort/logtape.c b/src/backend/utils/sort/logtape.c
index 666a7c0e81..4984f8ce50 100644
--- a/src/backend/utils/sort/logtape.c
+++ b/src/backend/utils/sort/logtape.c
@@ -782,7 +782,7 @@ LogicalTapeWrite(LogicalTapeSet *lts, int tapenum,
 	Assert(lt->buffer_size == BLCKSZ);
 	while (size > 0)
 	{
-		if (lt->pos >= TapeBlockPayloadSize)
+		if (lt->pos >= (int) TapeBlockPayloadSize)
 		{
 			/* Buffer full, dump it out */
 			long		nextBlockNumber;


[parent: aa7927698acb]