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Re: Compiler speed (vanilla vs. LTO, PGO and LTO+PGO)
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Markus Trippelsdorf <markus at trippelsdorf dot de>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, gcc_mailinglist at abwesend dot de, gcc-help at gcc dot gnu dot org, gcc at gcc dot gnu dot org
- Date: Tue, 26 Mar 2013 12:13:26 +0100
- Subject: Re: Compiler speed (vanilla vs. LTO, PGO and LTO+PGO)
- References: <trinity-46d93944-181a-4a69-836d-b1cd693c2d5c-1364154786327 at msvc024> <20130325070650 dot GA12504 at x4> <20130325125652 dot GB12504 at x4> <CAFiYyc0aYmpHewjRmHKRQARjKVb9ZHEhmqyYgJ5ewgO5Wjj4kQ at mail dot gmail dot com> <20130325132442 dot GD12504 at x4> <CAFiYyc2W2gkKqX9t7X09yXxsyeXL1uDugRjEweDE0y_u5VwnOg at mail dot gmail dot com> <20130325153423 dot GE12504 at x4>
> Yes, the binary size is 8-10% smaller. Unfortunately there are no performance
> improvements.
>
> LTO+PGO-disable-plugin:
> -rwxr-xr-x 1 markus markus 15025568 Mar 25 15:49 cc1
> -rwxr-xr-x 1 markus markus 16198584 Mar 25 15:49 cc1plus
> -rwxr-xr-x 1 markus markus 13907328 Mar 25 15:49 lto1
> -rwxr-xr-x 4 markus markus 492360 Mar 25 15:49 c++
> -rwxr-xr-x 1 markus markus 488240 Mar 25 15:49 cpp
> -rwxr-xr-x 3 markus markus 488216 Mar 25 15:49 gcc
>
> Firefox:
> LTO+PGO-disable-plugin: 4590.55s user 273.70s system 343% cpu 23:34.65 total
>
> kernel:
> LTO+PGO-disable-plugin:
> 344.11s user 23.59s system 322% cpu 1:54.08 total 340.94s user 23.65s system 326% cpu 1:51.56 total 339.66s user 23.41s system 329% cpu 1:50.09 total
Interesting, I was able to get faste LTO+PGO compile times than non-LTO,PGO.
I however did testng only on combine.c compliation, so not very scientific.
There are some cases FDO information is not streamed well in all cases. I will
post patch for that later today. Perhaps it will make situation bit better.
Honza