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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2007-09-25 22:11:48 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2007-09-25 22:11:48 +0000 |
| commit | 7a315a09dc0f7a1f903b89022a2a833c1719145b (patch) | |
| tree | 56bbb50df14a7caa843411446b291d2acbf117f9 /src/backend/storage/buffer/bufmgr.c | |
| parent | 6f5c38dcd0dfb391bcbaa683a96f4a62c574d95a (diff) | |
| download | postgresql-7a315a09dc0f7a1f903b89022a2a833c1719145b.tar.gz postgresql-7a315a09dc0f7a1f903b89022a2a833c1719145b.zip | |
Dept. of second thoughts: fix loop in BgBufferSync so that the exit when
bgwriter_lru_maxpages is exceeded leaves the loop variables in the
expected state. In the original coding, we'd fail to advance
next_to_clean, causing that buffer to be probably-uselessly rechecked next
time, and also have an off-by-one idea of the number of buffers scanned.
Diffstat (limited to 'src/backend/storage/buffer/bufmgr.c')
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 6ba935a09af..ce7c54deeec 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.225 2007/09/25 20:03:37 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.226 2007/09/25 22:11:48 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1324,10 +1324,17 @@ BgBufferSync(void) reusable_buffers = reusable_buffers_est; /* Execute the LRU scan */ - while (num_to_scan-- > 0 && reusable_buffers < upcoming_alloc_est) + while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est) { int buffer_state = SyncOneBuffer(next_to_clean, true); + if (++next_to_clean >= NBuffers) + { + next_to_clean = 0; + next_passes++; + } + num_to_scan--; + if (buffer_state & BUF_WRITTEN) { reusable_buffers++; @@ -1339,12 +1346,6 @@ BgBufferSync(void) } else if (buffer_state & BUF_REUSABLE) reusable_buffers++; - - if (++next_to_clean >= NBuffers) - { - next_to_clean = 0; - next_passes++; - } } BgWriterStats.m_buf_written_clean += num_written; @@ -1353,7 +1354,7 @@ BgBufferSync(void) elog(DEBUG1, "bgwriter: recent_alloc=%u smoothed=%.2f delta=%ld ahead=%d density=%.2f reusable_est=%d upcoming_est=%d scanned=%d wrote=%d reusable=%d", recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead, smoothed_density, reusable_buffers_est, upcoming_alloc_est, - bufs_to_lap - num_to_scan - 1, + bufs_to_lap - num_to_scan, num_written, reusable_buffers - reusable_buffers_est); #endif @@ -1366,7 +1367,7 @@ BgBufferSync(void) * scanning, which is helpful because a long memory isn't as desirable * on the density estimates. */ - strategy_delta = bufs_to_lap - num_to_scan - 1; + strategy_delta = bufs_to_lap - num_to_scan; recent_alloc = reusable_buffers - reusable_buffers_est; if (strategy_delta > 0 && recent_alloc > 0) { |