postgres.git / summary / log / commit / refs

commit    09f8bb5b3617269eb750b395fb561a2e532af221
Author:   Teodor Sigaev <teodor@sigaev.ru>
Date:     Mon Mar 20 15:49:41 2017 +0000

    Revert unintentional change in increasing usage count during pin of buffers,
    this makes buffer access strategy have no effect.
    Change was a part of commit 48354581a49c30f5757c203415aa8412d85b0f70 during 9.6
    release cycle, so backpath to 9.6
    
    Reported-by: Jim Nasby
    Author: Alexander Korotkov
    Reviewed-by: Jim Nasby, Andres Freund
    
    https://commitfest.postgresql.org/13/1029/


 src/backend/storage/buffer/bufmgr.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index a67fff69728..3a300305ecd 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1595,9 +1595,21 @@ PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
 			/* increase refcount */
 			buf_state += BUF_REFCOUNT_ONE;
 
-			/* increase usagecount unless already max */
-			if (BUF_STATE_GET_USAGECOUNT(buf_state) != BM_MAX_USAGE_COUNT)
-				buf_state += BUF_USAGECOUNT_ONE;
+			if (strategy == NULL)
+			{
+				/* Default case: increase usagecount unless already max. */
+				if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
+					buf_state += BUF_USAGECOUNT_ONE;
+			}
+			else
+			{
+				/*
+				 * Ring buffers shouldn't evict others from pool.  Thus we
+				 * don't make usagecount more than 1.
+				 */
+				if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
+					buf_state += BUF_USAGECOUNT_ONE;
+			}
 
 			if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
 											   buf_state))


[parent: 09079b72b7fd]