Re: Shared memory changes in 9.4?

Uh, this patch was never applied. Do we want it?

---------------------------------------------------------------------------

On Thu, Jun 12, 2014 at 03:39:14PM +0200, Christoph Berg wrote:
> Re: Andres Freund 2014-06-12 <20140612094112(dot)GZ8406(at)alap3(dot)anarazel(dot)de>
> > > * Make initdb determine the best shm type for this platform and write
> > > it into postgresql.conf as it does now.
> > > * If no dynamic_shared_memory_type is found in the config, default to
> > > "none".
> > > * Modify the three identical error messages concerned about shm
> > > segments to include the shm type instead of always just saying
> > > "FATAL: could not open shared memory segment"
> > > * Add a HINT to the POSIX error message:
> > > "HINT: This might indicate that /dev/shm is not mounted, or its
> > > permissions do not allow the database user to create files there"
> >
> > Sounds like a sane plan to me.
>
> Here are two patches, one that implements the annotated error
> messages, and one that selects none as default.
>
> It might also make sense to add a Note that POSIX depends on /dev/shm,
> and also a Note that dynamic_shared_memory_type is not related to
> the shared_buffers shm segments, which I didn't include here.
>
> Christoph
> --
> cb(at)df7cb(dot)de | http://www.df7cb.de/

> diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
> new file mode 100644
> index 0819641..780e3a5
> *** a/src/backend/storage/ipc/dsm_impl.c
> --- b/src/backend/storage/ipc/dsm_impl.c
> *************** dsm_impl_posix(dsm_op op, dsm_handle han
> *** 289,296 ****
> if (errno != EEXIST)
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not open shared memory segment \"%s\": %m",
> ! name)));
> return false;
> }
>
> --- 289,299 ----
> if (errno != EEXIST)
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not open POSIX shared memory segment \"%s\": %m",
> ! name),
> ! errhint("This error usually means that /dev/shm is not mounted, or its "
> ! "permissions do not allow the database user to create files "
> ! "there.")));
> return false;
> }
>
> *************** dsm_impl_posix(dsm_op op, dsm_handle han
> *** 313,319 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 316,322 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat POSIX shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_posix(dsm_op op, dsm_handle han
> *** 332,338 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not resize shared memory segment %s to %zu bytes: %m",
> name, request_size)));
> return false;
> }
> --- 335,341 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not resize POSIX shared memory segment %s to %zu bytes: %m",
> name, request_size)));
> return false;
> }
> *************** dsm_impl_posix(dsm_op op, dsm_handle han
> *** 358,364 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 361,367 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap POSIX shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_posix(dsm_op op, dsm_handle han
> *** 382,388 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 385,391 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map POSIX shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_sysv(dsm_op op, dsm_handle hand
> *** 512,518 ****
> errno = save_errno;
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not get shared memory segment: %m")));
> }
> return false;
> }
> --- 515,521 ----
> errno = save_errno;
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not get System V shared memory segment: %m")));
> }
> return false;
> }
> *************** dsm_impl_sysv(dsm_op op, dsm_handle hand
> *** 530,536 ****
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 533,539 ----
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap System V shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_sysv(dsm_op op, dsm_handle hand
> *** 540,546 ****
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not remove shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 543,549 ----
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not remove System V shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_sysv(dsm_op op, dsm_handle hand
> *** 556,562 ****
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 559,565 ----
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat System V shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_sysv(dsm_op op, dsm_handle hand
> *** 577,583 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 580,586 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map System V shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_windows(dsm_op op, dsm_handle h
> *** 645,651 ****
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 648,654 ----
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap Windows shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_windows(dsm_op op, dsm_handle h
> *** 655,661 ****
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not remove shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 658,664 ----
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not remove Windows shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_windows(dsm_op op, dsm_handle h
> *** 691,697 ****
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not create shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 694,700 ----
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not create Windows shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_windows(dsm_op op, dsm_handle h
> *** 718,724 ****
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not open shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 721,727 ----
> _dosmaperr(GetLastError());
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not open Windows shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_windows(dsm_op op, dsm_handle h
> *** 739,745 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 742,748 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map Windows shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_windows(dsm_op op, dsm_handle h
> *** 763,769 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 766,772 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat Windows shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 808,814 ****
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 811,817 ----
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap mmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 818,824 ****
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not remove shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 821,827 ----
> {
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not remove mmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 832,838 ****
> if (errno != EEXIST)
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not open shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 835,841 ----
> if (errno != EEXIST)
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not open mmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 856,862 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 859,865 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not stat mmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 875,881 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not resize shared memory segment %s to %zu bytes: %m",
> name, request_size)));
> return false;
> }
> --- 878,884 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not resize mmap shared memory segment %s to %zu bytes: %m",
> name, request_size)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 923,929 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not resize shared memory segment %s to %zu bytes: %m",
> name, request_size)));
> return false;
> }
> --- 926,932 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not resize mmap shared memory segment %s to %zu bytes: %m",
> name, request_size)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 950,956 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 953,959 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not unmap mmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> *************** dsm_impl_mmap(dsm_op op, dsm_handle hand
> *** 974,980 ****
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map shared memory segment \"%s\": %m",
> name)));
> return false;
> }
> --- 977,983 ----
>
> ereport(elevel,
> (errcode_for_dynamic_shared_memory(),
> ! errmsg("could not map mmap shared memory segment \"%s\": %m",
> name)));
> return false;
> }

> diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
> new file mode 100644
> index 697cf99..db52c77
> *** a/doc/src/sgml/config.sgml
> --- b/doc/src/sgml/config.sgml
> *************** include 'filename'
> *** 1416,1429 ****
> <literal>windows</> (for Windows shared memory), <literal>mmap</>
> (to simulate shared memory using memory-mapped files stored in the
> data directory), and <literal>none</> (to disable this feature).
> ! Not all values are supported on all platforms; the first supported
> ! option is the default for that platform. The use of the
> ! <literal>mmap</> option, which is not the default on any platform,
> is generally discouraged because the operating system may write
> modified pages back to disk repeatedly, increasing system I/O load;
> however, it may be useful for debugging, when the
> <literal>pg_dynshmem</> directory is stored on a RAM disk, or when
> other shared memory facilities are not available.
> </para>
> </listitem>
> </varlistentry>
> --- 1416,1432 ----
> <literal>windows</> (for Windows shared memory), <literal>mmap</>
> (to simulate shared memory using memory-mapped files stored in the
> data directory), and <literal>none</> (to disable this feature).
> ! Not all values are supported on all platforms.
> ! The use of the <literal>mmap</> option
> is generally discouraged because the operating system may write
> modified pages back to disk repeatedly, increasing system I/O load;
> however, it may be useful for debugging, when the
> <literal>pg_dynshmem</> directory is stored on a RAM disk, or when
> other shared memory facilities are not available.
> + <application>initdb</> will select a suitable setting for the system.
> + The default, when not configured explicitely in
> + <filename>postgresql.conf</>, is to disable the use of dynamic shared
> + memory.
> </para>
> </listitem>
> </varlistentry>
> diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
> new file mode 100644
> index 1d094f0..e73f6c1
> *** a/src/backend/utils/misc/guc.c
> --- b/src/backend/utils/misc/guc.c
> *************** static struct config_enum ConfigureNames
> *** 3453,3459 ****
> NULL
> },
> &dynamic_shared_memory_type,
> ! DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE, dynamic_shared_memory_options,
> NULL, NULL, NULL
> },
>
> --- 3453,3459 ----
> NULL
> },
> &dynamic_shared_memory_type,
> ! DSM_IMPL_NONE, dynamic_shared_memory_options,
> NULL, NULL, NULL
> },
>
> diff --git a/src/include/storage/dsm_impl.h b/src/include/storage/dsm_impl.h
> new file mode 100644
> index 6e2a013..aa3487a
> *** a/src/include/storage/dsm_impl.h
> --- b/src/include/storage/dsm_impl.h
> ***************
> *** 26,41 ****
> */
> #ifdef WIN32
> #define USE_DSM_WINDOWS
> - #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_WINDOWS
> #else
> #ifdef HAVE_SHM_OPEN
> #define USE_DSM_POSIX
> - #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_POSIX
> #endif
> #define USE_DSM_SYSV
> - #ifndef DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE
> - #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_SYSV
> - #endif
> #define USE_DSM_MMAP
> #endif
>
> --- 26,36 ----

>
> --
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--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +