Re: Test to dump and restore objects left behind by regression

On Fri, Mar 21, 2025 at 8:13 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>
> I passed PROVE_FLAGS="--timer -v" to get the timings and run under
> --format=directory.
>
> Without new test:
> ok    23400 ms ( 0.00 usr  0.00 sys +  2.84 cusr  1.53 csys =  4.37 CPU)
> ok    23409 ms ( 0.00 usr  0.01 sys +  2.81 cusr  1.53 csys =  4.35 CPU)
>
>
> With new test, under --format=directory:
> -j2 (parallel, default gzip compression)
> ok    27517 ms ( 0.00 usr  0.00 sys +  3.92 cusr  1.86 csys =  5.78 CPU)
> ok    27772 ms ( 0.01 usr  0.00 sys +  3.96 cusr  1.86 csys =  5.83 CPU)
> ok    27654 ms ( 0.00 usr  0.00 sys +  3.81 cusr  1.94 csys =  5.75 CPU)
> ok    27663 ms ( 0.00 usr  0.00 sys +  4.11 cusr  1.71 csys =  5.82 CPU)
>
> -j2 --compress=0
> ok    27710 ms ( 0.00 usr  0.00 sys +  3.79 cusr  1.86 csys =  5.65 CPU)
> ok    27567 ms ( 0.01 usr  0.00 sys +  3.67 cusr  1.96 csys =  5.64 CPU)
> ok    27582 ms ( 0.00 usr  0.00 sys +  3.60 cusr  1.90 csys =  5.50 CPU)
> ok    27519 ms ( 0.01 usr  0.00 sys +  3.71 cusr  1.80 csys =  5.52 CPU)
>
> -j2 --compress=zstd
> ok    27240 ms ( 0.01 usr  0.00 sys +  3.65 cusr  2.10 csys =  5.76 CPU)
> ok    27301 ms ( 0.01 usr  0.00 sys +  3.77 cusr  1.97 csys =  5.75 CPU)
>
> -j2 --compress=zstd:1
> ok    27695 ms ( 0.01 usr  0.00 sys +  3.66 cusr  2.05 csys =  5.72 CPU)
> ok    27671 ms ( 0.01 usr  0.00 sys +  3.76 cusr  1.95 csys =  5.72 CPU)
>
> --compress=zstd:1 (no parallelism)
> ok    28417 ms ( 0.01 usr  0.00 sys +  3.90 cusr  1.75 csys =  5.66 CPU)
> ok    28388 ms ( 0.00 usr  0.00 sys +  3.74 cusr  1.81 csys =  5.55 CPU)
>
> --compress=zstd (no parallelism)
> ok    28310 ms ( 0.00 usr  0.01 sys +  3.81 cusr  1.83 csys =  5.65 CPU)
> ok    28277 ms ( 0.01 usr  0.00 sys +  3.71 cusr  1.87 csys =  5.59 CPU)
>
>
> So apparently, zstd if available is a bit better than gzip and
> parallelism is better than no.  But the differences are small -- half a
> second or so.  The total increase in runtime in the best case is about
> four seconds.  In all cases I used the same parallelism in pg_restore
> than pg_dump; not sure if that could cause a difference.

I used the same parallelism in pg_restore and pg_dump too. And your
numbers seem to be similar to mine; slightly less than 20% slowdown.
But is that slowdown acceptable? From the earlier discussions, it
seems the answer is No. Haven't heard otherwise.

-- 
Best Wishes,
Ashutosh Bapat