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
