diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/aio/read_stream.c | 7 | ||||
| -rw-r--r-- | src/backend/utils/misc/postgresql.conf.sample | 4 | ||||
| -rw-r--r-- | src/include/port/pg_iovec.h | 8 |
3 files changed, 12 insertions, 7 deletions
diff --git a/src/backend/storage/aio/read_stream.c b/src/backend/storage/aio/read_stream.c index d65fa07b44c..45bdf819d57 100644 --- a/src/backend/storage/aio/read_stream.c +++ b/src/backend/storage/aio/read_stream.c @@ -515,9 +515,10 @@ read_stream_begin_impl(int flags, * finishes we don't want to have to wait for its buffers to be consumed * before starting a new one. * - * Be careful not to allow int16 to overflow (even though that's not - * possible with the current GUC range limits), allowing also for the - * spare entry and the overflow space. + * Be careful not to allow int16 to overflow. That is possible with the + * current GUC range limits, so this is an artificial limit of ~32k + * buffers and we'd need to adjust the types to exceed that. We also have + * to allow for the spare entry and the overflow space. */ max_pinned_buffers = (max_ios + 1) * io_combine_limit; max_pinned_buffers = Min(max_pinned_buffers, diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 66bda60f4ca..6abd1baeac8 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -200,9 +200,9 @@ #backend_flush_after = 0 # measured in pages, 0 disables #effective_io_concurrency = 16 # 1-1000; 0 disables prefetching #maintenance_io_concurrency = 16 # 1-1000; 0 disables prefetching -#io_max_combine_limit = 128kB # usually 1-32 blocks (depends on OS) +#io_max_combine_limit = 128kB # usually 1-128 blocks (depends on OS) # (change requires restart) -#io_combine_limit = 128kB # usually 1-32 blocks (depends on OS) +#io_combine_limit = 128kB # usually 1-128 blocks (depends on OS) #io_method = worker # worker, sync (change requires restart) #io_max_concurrency = -1 # Max number of IOs that one process diff --git a/src/include/port/pg_iovec.h b/src/include/port/pg_iovec.h index d9891d3805d..df40c7208be 100644 --- a/src/include/port/pg_iovec.h +++ b/src/include/port/pg_iovec.h @@ -33,8 +33,12 @@ struct iovec #endif -/* Define a reasonable maximum that is safe to use on the stack. */ -#define PG_IOV_MAX Min(IOV_MAX, 32) +/* + * Define a reasonable maximum that is safe to use on the stack in arrays of + * struct iovec and other small types. The operating system could limit us to + * a number as low as 16, but most systems have 1024. + */ +#define PG_IOV_MAX Min(IOV_MAX, 128) /* * Like preadv(), but with a prefix to remind us of a side-effect: on Windows |