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Add huge_page_size setting for use on Linux.

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This allows the huge page size to be set explicitly.  The default is 0,
meaning it will use the system default, as before.

Author: Odin Ugedal <odin@ugedal.com>
Discussion: https://postgr.es/m/20200608154639.20254-1-odin%40ugedal.com
This commit is contained in:
Thomas Munro
2020-07-17 14:33:00 +12:00
parent d66b23b032
commit d2bddc2500
6 changed files with 141 additions and 38 deletions
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62
src/backend/port/sysv_shmem.c
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@ -32,6 +32,7 @@
#endif
#include "miscadmin.h"
#include "port/pg_bitutils.h"
#include "portability/mem.h"
#include "storage/dsm.h"
#include "storage/fd.h"
@ -448,7 +449,7 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
#ifdef MAP_HUGETLB
/*
* Identify the huge page size to use.
* Identify the huge page size to use, and compute the related mmap flags.
*
* Some Linux kernel versions have a bug causing mmap() to fail on requests
* that are not a multiple of the hugepage size. Versions without that bug
@ -464,25 +465,13 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
* hugepage sizes, we might want to think about more invasive strategies,
* such as increasing shared_buffers to absorb the extra space.
*
* Returns the (real or assumed) page size into *hugepagesize,
* Returns the (real, assumed or config provided) page size into *hugepagesize,
* and the hugepage-related mmap flags to use into *mmap_flags.
*
* Currently *mmap_flags is always just MAP_HUGETLB. Someday, on systems
* that support it, we might OR in additional bits to specify a particular
* non-default huge page size.
*/
static void
GetHugePageSize(Size *hugepagesize, int *mmap_flags)
{
/*
* If we fail to find out the system's default huge page size, assume it
* is 2MB. This will work fine when the actual size is less. If it's
* more, we might get mmap() or munmap() failures due to unaligned
* requests; but at this writing, there are no reports of any non-Linux
* systems being picky about that.
*/
*hugepagesize = 2 * 1024 * 1024;
*mmap_flags = MAP_HUGETLB;
Size default_hugepagesize = 0;
/*
* System-dependent code to find out the default huge page size.
@ -491,6 +480,7 @@ GetHugePageSize(Size *hugepagesize, int *mmap_flags)
* nnnn kB". Ignore any failures, falling back to the preset default.
*/
#ifdef __linux__
{
FILE *fp = AllocateFile("/proc/meminfo", "r");
char buf[128];
@ -505,7 +495,7 @@ GetHugePageSize(Size *hugepagesize, int *mmap_flags)
{
if (ch == 'k')
{
*hugepagesize = sz * (Size) 1024;
default_hugepagesize = sz * (Size) 1024;
break;
}
/* We could accept other units besides kB, if needed */
@ -515,6 +505,44 @@ GetHugePageSize(Size *hugepagesize, int *mmap_flags)
}
}
#endif /* __linux__ */
if (huge_page_size != 0)
{
/* If huge page size is requested explicitly, use that. */
*hugepagesize = (Size) huge_page_size * 1024;
}
else if (default_hugepagesize != 0)
{
/* Otherwise use the system default, if we have it. */
*hugepagesize = default_hugepagesize;
}
else
{
/*
* If we fail to find out the system's default huge page size, or no
* huge page size is requested explicitly, assume it is 2MB. This will
* work fine when the actual size is less. If it's more, we might get
* mmap() or munmap() failures due to unaligned requests; but at this
* writing, there are no reports of any non-Linux systems being picky
* about that.
*/
*hugepagesize = 2 * 1024 * 1024;
}
*mmap_flags = MAP_HUGETLB;
/*
* On recent enough Linux, also include the explicit page size, if
* necessary.
*/
#if defined(MAP_HUGE_MASK) && defined(MAP_HUGE_SHIFT)
if (*hugepagesize != default_hugepagesize)
{
int shift = pg_ceil_log2_64(*hugepagesize);
*mmap_flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
}
#endif
}
#endif /* MAP_HUGETLB */
@ -583,7 +611,7 @@ CreateAnonymousSegment(Size *size)
"(currently %zu bytes), reduce PostgreSQL's shared "
"memory usage, perhaps by reducing shared_buffers or "
"max_connections.",
*size) : 0));
allocsize) : 0));
}
*size = allocsize;