On Tue, Oct 22, 2024 at 02:54:57PM -0500, Nathan Bossart wrote: > My colleague Salvatore Dipietro (CC'd) sent me a couple of profiles that > showed an enormous amount of s_lock() time going to the > __sync_lock_test_and_set() call in the AArch64 implementation of tas(). > Upon closer inspection, I noticed that we don't implement a custom > TAS_SPIN() for this architecture, so I quickly hacked together the attached > patch and ran a couple of benchmarks that stressed the spinlock code. I > found no discussion about TAS_SPIN() on ARM in the archives, but I did > notice that the initial AArch64 support was added [0] before x86_64 started > using a non-locking test [1]. > > These benchmarks are for a c8g.24xlarge running a select-only pgbench with > 256 clients and pg_stat_statements.track_planning enabled. > > without the patch: > > [...] > > tps = 74135.100891 (without initial connection time) > > with the patch: > > [...] > > tps = 549462.785554 (without initial connection time)
Are there any objections to proceeding with this change? So far, it's been tested on a c8g.24xlarge and an Apple M3 (which seems to be too small to show any effect). If anyone has access to a larger ARM machine, additional testing would be greatly appreciated. I think it would be unfortunate if this slipped to v19. -- nathan
