Hi, On 2024-12-19 17:29:12 -0500, Andres Freund wrote: > > Not about patch itself, but questions about related stack functionality: > > ---------------------------------------------------------------------------------------------------- > > > > > > 7. Is pg_stat_aios still on the table or not ? (AIO 2021 had it). Any hints > > on how to inspect real I/O calls requested to review if the code is issuing > > sensible calls: there's no strace for uring, or do you stick to DEBUG3 or > > perhaps using some bpftrace / xfsslower is the best way to go ? > > I think we still want something like it, but I don't think it needs to be in > the initial commits.
After I got this question from Thomas as well, I started hacking one up. What information would you like to see? Here's what I currently have: ┌─[ RECORD 1 ]───┬────────────────────────────────────────────────┐ │ pid │ 358212 │ │ io_id │ 2050 │ │ io_generation │ 4209 │ │ state │ COMPLETED_SHARED │ │ operation │ read │ │ offset │ 509083648 │ │ length │ 262144 │ │ subject │ smgr │ │ iovec_data_len │ 32 │ │ raw_result │ 262144 │ │ result │ OK │ │ error_desc │ (null) │ │ subject_desc │ blocks 1372864..1372895 in file "base/5/16388" │ │ flag_sync │ f │ │ flag_localmem │ f │ │ flag_buffered │ t │ ├─[ RECORD 2 ]───┼────────────────────────────────────────────────┤ │ pid │ 358212 │ │ io_id │ 2051 │ │ io_generation │ 4199 │ │ state │ IN_FLIGHT │ │ operation │ read │ │ offset │ 511967232 │ │ length │ 262144 │ │ subject │ smgr │ │ iovec_data_len │ 32 │ │ raw_result │ (null) │ │ result │ UNKNOWN │ │ error_desc │ (null) │ │ subject_desc │ blocks 1373216..1373247 in file "base/5/16388" │ │ flag_sync │ f │ │ flag_localmem │ f │ │ flag_buffered │ t │ I didn't think that pg_stat_* was quite the right namespace, given that it shows not stats, but the currently ongoing IOs. I am going with pg_aios for now, but I don't particularly like that. I think we'll want a pg_stat_aio as well, tracking things like: - how often the queue to IO workes was full - how many times we submitted IO to the kernel (<= #ios with io_uring) - how many times we asked the kernel for events (<= #ios with io_uring) - how many times we had to wait for in-flight IOs before issuing more IOs Greetings, Andres Freund
