Allow using huge TLB pages on Linux (MAP_HUGETLB)

Enterprise / PostgreSQL - Heikki Linnakangas [iki.fi] - 29 January 2014 06:08 UTC

This patch adds an option, huge_tlb_pages, which allows requesting the shared memory segment to be allocated using huge pages, by using the MAP_HUGETLB flag in mmap(). This can improve performance.

The default is 'try', which means that we will attempt using huge pages, and fall back to non-huge pages if it doesn't work. Currently, only Linux has MAP_HUGETLB. On other platforms, the default 'try' behaves the same as 'off'.

In the passing, don't try to round the mmap() size to a multiple of pagesize. mmap() doesn't require that, and there's no particular reason for PostgreSQL to do that either. When using MAP_HUGETLB, however, round the request size up to nearest 2MB boundary. This is to work around a bug in some Linux kernel versions, but also to avoid wasting memory, because the kernel will round the size up anyway.

Many people were involved in writing this patch, including Christian Kruse, Richard Poole, Abhijit Menon-Sen, reviewed by Peter Geoghegan, Andres Freund and me.

1a3458b Allow using huge TLB pages on Linux (MAP_HUGETLB)
doc/src/sgml/config.sgml | 37 +++++++
src/backend/port/sysv_shmem.c | 135 ++++++++++++++++++-------
src/backend/port/win32_shmem.c | 5 +
src/backend/utils/misc/guc.c | 33 ++++++
src/backend/utils/misc/postgresql.conf.sample | 2 +
src/include/storage/pg_shmem.h | 10 ++
6 files changed, 183 insertions(+), 39 deletions(-)

Upstream: git.postgresql.org

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