diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/buffer/freelist.c | 46 |
1 files changed, 44 insertions, 2 deletions
diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..e1f8e5e97bd 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -555,8 +555,50 @@ GetAccessStrategy(BufferAccessStrategyType btype) return NULL; case BAS_BULKREAD: - ring_size_kb = 256; - break; + { + int ring_max_kb; + + /* + * The ring always needs to be large enough to allow some + * separation in time between providing a buffer to the user + * of the strategy and that buffer being reused. Otherwise the + * user's pin will prevent reuse of the buffer, even without + * concurrent activity. + * + * We also need to ensure the ring always is large enough for + * SYNC_SCAN_REPORT_INTERVAL, as noted above. + * + * Thus we start out a minimal size and increase the size + * further if appropriate. + */ + ring_size_kb = 256; + + /* + * There's no point in a larger ring if we won't be allowed to + * pin sufficiently many buffers. But we never limit to less + * than the minimal size above. + */ + ring_max_kb = GetPinLimit() * (BLCKSZ / 1024); + ring_max_kb = Max(ring_size_kb, ring_max_kb); + + /* + * We would like the ring to additionally have space for the + * the configured degree of IO concurrency. While being read + * in, buffers can obviously not yet be reused. + * + * Each IO can be up to io_combine_limit blocks large, and we + * want to start up to effective_io_concurrency IOs. + * + * Note that effective_io_concurrency may be 0, which disables + * AIO. + */ + ring_size_kb += (BLCKSZ / 1024) * + io_combine_limit * effective_io_concurrency; + + if (ring_size_kb > ring_max_kb) + ring_size_kb = ring_max_kb; + break; + } case BAS_BULKWRITE: ring_size_kb = 16 * 1024; break; |