Re: [PoC] Improve dead tuple storage for lazy vacuum

On Fri, Feb 24, 2023 at 3:41 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
wrote:
>
> In v29 vacuum took twice as long (286 s vs. 573 s)?

Not sure what happened there, and clearly I was looking at the wrong number
:/
I scripted the test for reproducibility and ran it three times. Also
included some variations (attached):

UUID times look comparable here, so no speedup or regression:

master:
system usage: CPU: user: 216.05 s, system: 35.81 s, elapsed: 634.22 s
system usage: CPU: user: 173.71 s, system: 31.24 s, elapsed: 599.04 s
system usage: CPU: user: 171.16 s, system: 30.21 s, elapsed: 583.21 s

v29:
system usage: CPU: user: 93.47 s, system: 40.92 s, elapsed: 594.10 s
system usage: CPU: user: 99.58 s, system: 44.73 s, elapsed: 606.80 s
system usage: CPU: user: 96.29 s, system: 42.74 s, elapsed: 600.10 s

Then, I tried sequential integers, which is a much more favorable access
pattern in general, and the new tid storage shows substantial improvement:

master:
system usage: CPU: user: 100.39 s, system: 7.79 s, elapsed: 121.57 s
system usage: CPU: user: 104.90 s, system: 8.81 s, elapsed: 124.24 s
system usage: CPU: user: 95.04 s, system: 7.55 s, elapsed: 116.44 s

v29:
system usage: CPU: user: 24.57 s, system: 8.53 s, elapsed: 61.07 s
system usage: CPU: user: 23.18 s, system: 8.25 s, elapsed: 58.99 s
system usage: CPU: user: 23.20 s, system: 8.98 s, elapsed: 66.86 s

That's fast enough that I thought an improvement would show up even with
standard WAL logging (no separate attachment, since it's a trivial change).
Seems a bit faster:

master:
system usage: CPU: user: 152.27 s, system: 11.76 s, elapsed: 216.86 s
system usage: CPU: user: 137.25 s, system: 11.07 s, elapsed: 213.62 s
system usage: CPU: user: 149.48 s, system: 12.15 s, elapsed: 220.96 s

v29:
system usage: CPU: user: 40.88 s, system: 15.99 s, elapsed: 170.98 s
system usage: CPU: user: 41.33 s, system: 15.45 s, elapsed: 166.75 s
system usage: CPU: user: 41.51 s, system: 18.20 s, elapsed: 203.94 s

There is more we could test here, but I feel better about these numbers.

In the next few days, I'll resume style review and list the remaining
issues we need to address.

--
John Naylor
EDB: http://www.enterprisedb.com