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Does it help to wait before reattaching?

Revert the map/unmap dance I tried in commit73042b8; that helpsnot at all.Instead, speculate that the unwanted allocation is being done onanother thread, and thus timing variations explain the apparentunpredictability. Temporarily add a 1-second sleep before theVirtualFree call, in hopes that any such other threads willquiesce and not jog our elbow.This is obviously not a desirable long-term fix, but as a means ofinvestigation it seems useful.Discussion:https://postgr.es/m/25495.1524517820@sss.pgh.pa.us

1 parent73042b8 commit2307868Copy full SHA for 2307868

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src/backend/port
- win32_shmem.c

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`‎src/backend/port/win32_shmem.c`

Lines changed: 4 additions & 15 deletions

Original file line number	Diff line number	Diff line change
`@@ -456,22 +456,11 @@ PGSharedMemoryReAttach(void)`
`456`	`456`	`/* Ensure buf is big enough that it won't grow mid-operation */`
`457`	`457`	`initStringInfo(&buf);`
`458`	`458`	`enlargeStringInfo(&buf,128*1024);`
	`459`	`+/* ... and let's just be sure all that space is committed */`
	`460`	`+memset(buf.data,0,buf.maxlen);`
`459`	`461`
`460`		`-dumpmem(&buf,"beginning PGSharedMemoryReAttach");`
`461`		`-`
`462`		`-hdr= (PGShmemHeader*)MapViewOfFileEx(UsedShmemSegID,FILE_MAP_READ \|FILE_MAP_WRITE,0,0,0,NULL);`
`463`		`-if (hdr)`
`464`		`-{`
`465`		`-if (!UnmapViewOfFile(hdr))`
`466`		`-elog(LOG,"could not unmap temporary view of shared memory: error code %lu",`
`467`		`-GetLastError());`
`468`		`-}`
`469`		`-else`
`470`		`-{`
`471`		`-/* This isn't fatal, just unpromising ... */`
`472`		`-elog(LOG,"could not attach to shared memory (key=%p) at any address: error code %lu",`
`473`		`-UsedShmemSegID,GetLastError());`
`474`		`-}`
	`462`	`+/* Test: see if this lets the process address space quiesce */`
	`463`	`+pg_usleep(1000000L);`
`475`	`464`
`476`	`465`	`dumpmem(&buf,"before VirtualFree");`
`477`	`466`

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Commit2307868

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`‎src/backend/port/win32_shmem.c`

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