On Fri, Feb 17, 2023 at 09:31:14AM -0800, Andres Freund wrote: > On 2023-02-17 16:19:46 +0900, Michael Paquier wrote: >> But it looks like I misunderstood what this quote meant compared to >> what v3 does. It is true that v3 sets iov_len and iov_base more than >> needed when writing sizes larger than BLCKSZ. > > I don't think it does for writes larger than BLCKSZ, it just does more for > writes larger than PG_IKOV_MAX * BLCKSZ. But in those cases CPU time is going > to be spent elsewhere.
Yep. >> Seems like you think that it is not really going to matter much to track >> which iovecs have been already initialized during the first loop on >> pg_pwritev_with_retry() to keep the code shorter? > > Yes. I'd bet that, in the unlikely case you're going to see any difference at > all, unconditionally initializing is going to win. > > Right now we memset() 8KB, and iterate over 32 IOVs, unconditionally, on every > call. Even if we could do some further optimizations of what I did in the > patch, you can initialize needed IOVs repeatedly a *lot* of times, before it > shows up... > > I'm inclined to go with my version, with the argument order swapped to > Bharath's order. Okay. That's fine by me. -- Michael
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