Cleanup of pg_numa.c

This moves/renames some of the functions defined in pg_numa.c:

* pg_numa_get_pagesize() is renamed to pg_get_shmem_pagesize(), and
  moved to src/backend/storage/ipc/shmem.c. The new name better reflects
  that the page size is not related to NUMA, and it's specifically about
  the page size used for the main shared memory segment.

* move pg_numa_available() to src/backend/storage/ipc/shmem.c, i.e. into
  the backend (which more appropriate for functions callable from SQL).
  While at it, improve the comment to explain what page size it returns.

* remove unnecessary includes from src/port/pg_numa.c, adding
  unnecessary dependencies (src/port should be suitable for frontent).
  These were either leftovers or unnecessary thanks to the other changes
  in this commit.

This eliminates unnecessary dependencies on backend symbols, which we
don't want in src/port.

Reported-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
https://postgr.es/m/CALdSSPi5fj0a7UG7Fmw2cUD1uWuckU_e8dJ+6x-bJEokcSXzqA@mail.gmail.com

contrib/pg_buffercache/pg_buffercache_pages.c

@@ -343,7 +343,7 @@ pg_buffercache_numa_pages(PG_FUNCTION_ARGS)
 		 * This information is needed before calling move_pages() for NUMA
 		 * node id inquiry.
 		 */
-		os_page_size = pg_numa_get_pagesize();
+		os_page_size = pg_get_shmem_pagesize();
 
 		/*
 		 * The pages and block size is expected to be 2^k, so one divides the

src/backend/storage/ipc/shmem.c

@@ -93,6 +93,8 @@ static HTAB *ShmemIndex = NULL; /* primary index hashtable for shmem */
 /* To get reliable results for NUMA inquiry we need to "touch pages" once */
 static bool firstNumaTouch = true;
 
+Datum		pg_numa_available(PG_FUNCTION_ARGS);
+
 /*
  *	InitShmemAccess() --- set up basic pointers to shared memory.
  */
@@ -615,7 +617,7 @@ pg_get_shmem_allocations_numa(PG_FUNCTION_ARGS)
 	 * This information is needed before calling move_pages() for NUMA memory
 	 * node inquiry.
 	 */
-	os_page_size = pg_numa_get_pagesize();
+	os_page_size = pg_get_shmem_pagesize();
 
 	/*
 	 * Allocate memory for page pointers and status based on total shared
@@ -727,3 +729,39 @@ pg_get_shmem_allocations_numa(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * Determine the memory page size used for the shared memory segment.
+ *
+ * If the shared segment was allocated using huge pages, returns the size of
+ * a huge page. Otherwise returns the size of regular memory page.
+ *
+ * This should be used only after the server is started.
+ */
+Size
+pg_get_shmem_pagesize(void)
+{
+	Size		os_page_size;
+#ifdef WIN32
+	SYSTEM_INFO sysinfo;
+
+	GetSystemInfo(&sysinfo);
+	os_page_size = sysinfo.dwPageSize;
+#else
+	os_page_size = sysconf(_SC_PAGESIZE);
+#endif
+
+	Assert(IsUnderPostmaster);
+	Assert(huge_pages_status != HUGE_PAGES_UNKNOWN);
+
+	if (huge_pages_status == HUGE_PAGES_ON)
+		GetHugePageSize(&os_page_size, NULL);
+
+	return os_page_size;
+}
+
+Datum
+pg_numa_available(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_BOOL(pg_numa_init() != -1);
+}

src/include/port/pg_numa.h

@@ -14,12 +14,9 @@
 #ifndef PG_NUMA_H
 #define PG_NUMA_H
 
-#include "fmgr.h"
-
 extern PGDLLIMPORT int pg_numa_init(void);
 extern PGDLLIMPORT int pg_numa_query_pages(int pid, unsigned long count, void **pages, int *status);
 extern PGDLLIMPORT int pg_numa_get_max_node(void);
-extern PGDLLIMPORT Size pg_numa_get_pagesize(void);
 
 #ifdef USE_LIBNUMA
 

src/include/storage/shmem.h

@@ -41,6 +41,8 @@ extern void *ShmemInitStruct(const char *name, Size size, bool *foundPtr);
 extern Size add_size(Size s1, Size s2);
 extern Size mul_size(Size s1, Size s2);
 
+extern PGDLLIMPORT Size pg_get_shmem_pagesize(void);
+
 /* ipci.c */
 extern void RequestAddinShmemSpace(Size size);
 

src/port/pg_numa.c

@@ -13,17 +13,10 @@
  *-------------------------------------------------------------------------
  */
 
-#include "postgres.h"
+#include "c.h"
 #include <unistd.h>
 
-#ifdef WIN32
-#include <windows.h>
-#endif
-
-#include "fmgr.h"
-#include "miscadmin.h"
 #include "port/pg_numa.h"
-#include "storage/pg_shmem.h"
 
 /*
  * At this point we provide support only for Linux thanks to libnuma, but in
@@ -36,8 +29,6 @@
 #include <numa.h>
 #include <numaif.h>
 
-Datum		pg_numa_available(PG_FUNCTION_ARGS);
-
 /* libnuma requires initialization as per numa(3) on Linux */
 int
 pg_numa_init(void)
@@ -66,8 +57,6 @@ pg_numa_get_max_node(void)
 
 #else
 
-Datum		pg_numa_available(PG_FUNCTION_ARGS);
-
 /* Empty wrappers */
 int
 pg_numa_init(void)
@@ -89,32 +78,3 @@ pg_numa_get_max_node(void)
 }
 
 #endif
-
-Datum
-pg_numa_available(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_BOOL(pg_numa_init() != -1);
-}
-
-/* This should be used only after the server is started */
-Size
-pg_numa_get_pagesize(void)
-{
-	Size		os_page_size;
-#ifdef WIN32
-	SYSTEM_INFO sysinfo;
-
-	GetSystemInfo(&sysinfo);
-	os_page_size = sysinfo.dwPageSize;
-#else
-	os_page_size = sysconf(_SC_PAGESIZE);
-#endif
-
-	Assert(IsUnderPostmaster);
-	Assert(huge_pages_status != HUGE_PAGES_UNKNOWN);
-
-	if (huge_pages_status == HUGE_PAGES_ON)
-		GetHugePageSize(&os_page_size, NULL);
-
-	return os_page_size;
-}