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Add pg_memory_is_all_zeros() in memutils.h

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This new function tests if a memory region starting at a given location
for a defined length is made only of zeroes.  This unifies in a single
path the all-zero checks that were happening in a couple of places of
the backend code:
- For pgstats entries of relation, checkpointer and bgwriter, where
some "all_zeroes" variables were previously used with memcpy().
- For all-zero buffer pages in PageIsVerifiedExtended().

This new function uses the same forward scan as the check for all-zero
buffer pages, applying it to the three pgstats paths mentioned above.

Author: Bertrand Drouvot
Reviewed-by: Peter Eisentraut, Heikki Linnakangas, Peter Smith
Discussion: https://postgr.es/m/ZupUDDyf1hHI4ibn@ip-10-97-1-34.eu-west-3.compute.internal
This commit is contained in:
Michael Paquier
2024-11-01 11:35:46 +09:00
parent 49d6c7d8da
commit 07e9e28b56
5 changed files with 26 additions and 23 deletions
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13
src/backend/storage/page/bufpage.c
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@@ -89,10 +89,8 @@ PageIsVerifiedExtended(Page page, BlockNumber blkno, int flags)
{
PageHeader p = (PageHeader) page;
size_t *pagebytes;
int i;
bool checksum_failure = false;
bool header_sane = false;
bool all_zeroes = false;
uint16 checksum = 0;
/*
@@ -126,18 +124,9 @@ PageIsVerifiedExtended(Page page, BlockNumber blkno, int flags)
}
/* Check all-zeroes case */
all_zeroes = true;
pagebytes = (size_t *) page;
for (i = 0; i < (BLCKSZ / sizeof(size_t)); i++)
{
if (pagebytes[i] != 0)
{
all_zeroes = false;
break;
}
}
if (all_zeroes)
if (pg_memory_is_all_zeros(pagebytes, (BLCKSZ / sizeof(size_t))))
return true;
/*