Hi, On 2018-02-27 16:03:17 -0500, Robert Haas wrote: > On Wed, Feb 7, 2018 at 1:41 PM, Andres Freund <and...@anarazel.de> wrote: > > Well, it's more than just systems like that - for 64bit atomics we > > sometimes do fall back to spinlock based atomics on 32bit systems, even > > if they support 32 bit atomics. > > I built with -m32 on my laptop and tried "select aid, count(*) from > pgbench_accounts group by 1 having count(*) > 1" on pgbench at scale > factor 100 with pgbench_accounts_pkey dropped and > max_parallel_workers_per_gather set to 10 on (a) commit > 0b5e33f667a2042d7022da8bef31a8be5937aad1 (I know this is a little old, > but I think it doesn't matter), (b) same plus > shm-mq-less-spinlocks-v3, and (c) same plus shm-mq-less-spinlocks-v3 > and shm-mq-reduce-receiver-latch-set-v2. > > (a) 16563.790 ms, 16625.257 ms, 16496.062 ms > (b) 17217.051 ms, 17157.745 ms, 17225.755 ms [median to median +3.9% vs. (a)] > (c) 15491.947 ms, 15455.840 ms, 15452.649 ms [median to median -7.0% > vs. (a), -10.2% vs (b)] > > Do you think that's a problem? If it is, what do you think we should > do about it? It seems to me that it's probably OK because (1) with > both patches we still come out ahead and (2) 32-bit systems will > presumably continue to become rarer as time goes on, but you might > disagree.
No, I think this is fairly reasonable. A fairly extreme usecase on a 32 bit machine regressing a bit, while gaining peformance in other case? That works for me. > OK, I'll try to check how feasible that would be. cool. Greetings, Andres Freund
