diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/aio/read_stream.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/src/backend/storage/aio/read_stream.c b/src/backend/storage/aio/read_stream.c index 99e44ed99fe..04bdb5e6d4b 100644 --- a/src/backend/storage/aio/read_stream.c +++ b/src/backend/storage/aio/read_stream.c @@ -447,13 +447,17 @@ read_stream_begin_impl(int flags, /* * Choose the maximum number of buffers we're prepared to pin. We try to - * pin fewer if we can, though. We clamp it to at least io_combine_limit - * so that we can have a chance to build up a full io_combine_limit sized - * read, even when max_ios is zero. 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. + * pin fewer if we can, though. We add one so that we can make progress + * even if max_ios is set to 0 (see also further down). For max_ios > 0, + * this also allows an extra full I/O's worth of buffers: after an I/O + * 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. */ - max_pinned_buffers = Max(max_ios * 4, io_combine_limit); + max_pinned_buffers = (max_ios + 1) * io_combine_limit; max_pinned_buffers = Min(max_pinned_buffers, PG_INT16_MAX - io_combine_limit - 1); @@ -725,7 +729,7 @@ read_stream_next_buffer(ReadStream *stream, void **per_buffer_data) stream->ios[stream->oldest_io_index].buffer_index == oldest_buffer_index) { int16 io_index = stream->oldest_io_index; - int16 distance; + int32 distance; /* wider temporary value, clamped below */ /* Sanity check that we still agree on the buffers. */ Assert(stream->ios[io_index].op.buffers == |