Hi, Victor
On Thu, Jan 16, 2020 at 10:11 AM Victor Leschuk <vleschuk@xxxxxxxxx> wrote:
>
> Grepping bottleneck is not cpu, but IO. Maybe it is more reasonable to
> use not online_cpus() but online_cpus()*2?
I also tried this approach, but the tests I ran with online_cpus() * 2
only showed slowdowns. The results can be seen in the commit message:
> On Thu, Jan 16, 2020 at 5:41 AM Matheus Tavares
> <matheus.bernardino@xxxxxx> wrote:
> >
[...]
> > The following measurements correspond to the
> > mean elapsed times for 30 git-grep executions in chromium's
> > repository[1] with a 95% confidence interval (each set of 30 were
> > performed after 2 warmup runs). Regex 1 is 'abcd[02]' and Regex 2 is
> > '(static|extern) (int|double) \*'.
> >
> > | Working tree | Object Store
> > ------|-------------------------------|--------------------------------
> > #ths | Regex 1 | Regex 2 | Regex 1 | Regex 2
> > ------|---------------|---------------|----------------|---------------
> > 32 | 2.92s ± 0.01 | 3.72s ± 0.21 | 5.36s ± 0.01 | 6.07s ± 0.01
> > 16 | 2.84s ± 0.01 | 3.57s ± 0.21 | 5.05s ± 0.01 | 5.71s ± 0.01
> > > 8 | 2.53s ± 0.00 | 3.24s ± 0.21 | 4.86s ± 0.01 | 5.48s ± 0.01
> > 4 | 2.43s ± 0.02 | 3.22s ± 0.20 | 5.22s ± 0.02 | 6.03s ± 0.02
> > 2 | 3.06s ± 0.20 | 4.52s ± 0.01 | 7.52s ± 0.01 | 9.06s ± 0.01
> > 1 | 6.16s ± 0.01 | 9.25s ± 0.02 | 14.10s ± 0.01 | 17.22s ± 0.01
> >
> > The above tests were performed in a desktop running Debian 10.0 with
> > Intel(R) Xeon(R) CPU E3-1230 V2 (4 cores w/ hyper-threading), 32GB of
> > RAM and a 7200 rpm, SATA 3.1 HDD.
> >
> > Bellow, the tests were repeated for a machine with SSD: a Manjaro laptop
> > with Intel(R) i7-7700HQ (4 cores w/ hyper-threading) and 16GB of RAM:
> >
> > | Working tree | Object Store
> > ------|--------------------------------|--------------------------------
> > #ths | Regex 1 | Regex 2 | Regex 1 | Regex 2
> > ------|---------------|----------------|----------------|---------------
> > 32 | 3.29s ± 0.21 | 4.30s ± 0.01 | 6.30s ± 0.01 | 7.30s ± 0.02
> > 16 | 3.19s ± 0.20 | 4.14s ± 0.02 | 5.91s ± 0.01 | 6.83s ± 0.01
> > > 8 | 2.90s ± 0.04 | 3.82s ± 0.20 | 5.70s ± 0.02 | 6.53s ± 0.01
> > 4 | 2.84s ± 0.02 | 3.77s ± 0.20 | 6.19s ± 0.02 | 7.18s ± 0.02
> > 2 | 3.73s ± 0.21 | 5.57s ± 0.02 | 9.28s ± 0.01 | 11.22s ± 0.01
> > 1 | 7.48s ± 0.02 | 11.36s ± 0.03 | 17.75s ± 0.01 | 21.87s ± 0.08
I deliberately used somehow complex regexes for these tests. So I
decided to do one more test with a very simple fixed string ("abc"),
allowing git-grep to spend less time in the cpu-bound regex searching.
The results can be seen bellow (the metodology is the same as described
above and the machine is the Manjaro laptop, for which online_cpus()
returns 8):
#ths | Working Three | Object Store
------|----------------|---------------
16 | 3.22s ± 0.20 | 5.96s ± 0.06
8 | 2.92s ± 0.01 | 5.73s ± 0.02
