On March 25, 2016 1:04:13 PM GMT+01:00, Robert Haas <robertmh...@gmail.com> wrote: >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.
Last time I proposed that it got shut down. I agree it'd be a good idea, it's really hard to find alignment issues. -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
