Hi, On 2026-01-13 00:58:49 +0100, Tomas Vondra wrote: > On 1/10/26 02:42, Andres Freund wrote: > > psql -Xq -c 'SELECT pg_buffercache_evict_all();' -c 'SELECT numa_node, > > sum(size) FROM pg_shmem_allocations_numa GROUP BY 1;' && perf stat > > --per-socket -M memory_bandwidth_read,memory_bandwidth_write -a psql -c > > 'SELECT sum(abalance) FROM pgbench_accounts;'
> And then I initialized pgbench with scale that is much larger than > shared buffers, but fits into RAM. So cached, but definitely > NB/4. And > then I ran > > select * from pgbench_accounts offset 1000000000; > > which does a sequential scan with the circular buffer you mention abobe Did you try it with the query I suggested? One plausible reason why you did not see an effect with your query is that with a huge offset you actually never deform the tuple, which is an important and rather latency sensitive path. Greetings, Andres Freund
