Re: LogwrtResult contended spinlock

Hi

On 2024-Jun-29, Alexander Lakhin wrote:

> ----------------------------------- stderr -----------------------------------
> TRAP: failed Assert("TYPEALIGN(8, (uintptr_t)(&currval)) ==
> (uintptr_t)(&currval)"), File: "...\src\include\port/atomics.h", Line: 597,
> PID: 7556
> child process was terminated by exception 0xC0000409

Oh. This is the new assertion in pg_atomic_monotonic_advance_u64() and
therefore the only possible culprit could be logInsertResult in
XLogCtlData. Does it work if you do this?

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8dcdf5a764..e581488d57 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -468,7 +468,7 @@ typedef struct XLogCtlData
XLogRecPtr lastSegSwitchLSN;

/* These are accessed using atomics -- info_lck not needed */
- pg_atomic_uint64 logInsertResult; /* last byte + 1 inserted to buffers */
+ pg_atomic_uint64 logInsertResult pg_attribute_aligned(8); /* last byte + 1 inserted to buffers */
pg_atomic_uint64 logWriteResult; /* last byte + 1 written out */
pg_atomic_uint64 logFlushResult; /* last byte + 1 flushed */

Thanks

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"Use it up, wear it out, make it do, or do without"