On Fri, Mar 25, 2016 at 3:05 AM, Andres Freund <and...@anarazel.de> wrote: > On 2015-11-12 19:59:54 +0000, Robert Haas wrote: >> Move each SLRU's lwlocks to a separate tranche. >> >> This makes it significantly easier to identify these lwlocks in >> LWLOCK_STATS or Trace_lwlocks output. It's also arguably better >> from a modularity standpoint, since lwlock.c no longer needs to >> know anything about the LWLock needs of the higher-level SLRU >> facility. >> >> Ildus Kurbangaliev, reviewd by Álvaro Herrera and by me. > > Before this commit the lwlocks were cacheline aligned, but that's not > the case anymore afterwards; afaics. I think that should be fixed? I > guess it'd be good to avoid duplicating the code for aligning, so maybe > we ought to add a ShmemAllocAligned or something?
Does it actually matter? I wouldn't have thought the I/O locks had enough traffic for it to make any difference. But in any case I think the right solution is probably this: --- a/src/backend/storage/ipc/shmem.c +++ b/src/backend/storage/ipc/shmem.c @@ -173,7 +173,7 @@ ShmemAlloc(Size size) /* * ensure all space is adequately aligned. */ - size = MAXALIGN(size); + size = CACHELINEALIGN(size); Assert(ShmemSegHdr != NULL); It's stupid that we keep spending time and energy figuring out which shared memory data structures require alignment and which ones don't. Let's just align them *all* and be done with it. The memory cost shouldn't be more than a few kB. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers