Re: Streaming I/O, vectored I/O (WIP)

On Tue, Mar 12, 2024 at 11:39 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> + actual_nblocks = operation->nblocks = *nblocks = i + 1;
> (Dilip: I think we should break after this?)

In the next loop, i < actual_nblocks is false so the loop terminates.
But yeah that was a bit obscure, so I have added an explicit break.

Here also is a new version also of the streaming_read.c patch.  This
is based on feedback from the bitmap heap scan thread, where Tomas and
Melanie noticed some problems when comparing effective_io_concurrency
= 0 and 1 against master.  The attached random.sql exercises a bunch
of random scans with different settings, and random.txt shows the
resulting system calls, unpatched vs patched.  Looking at it that way,
I was able to tweak the coding until I had the same behaviour as
master, except with fewer system calls wherever possible due to
coalescing or suppressing sequential advice.