On Wed, Jun 29, 2022 at 3:39 PM Maxim Kuvyrkov <maxim.kuvyr...@linaro.org>
wrote:

> To add to David's answer, here is the logic that enables ccache in
> Linaro-maintained buildbots:
> https://git.linaro.org/ci/dockerfiles.git/tree/tcwg-base/tcwg-llvmbot/run.sh#n48
> .
>

Nice trick!

>
> We have experimented with using zorg's CCACHE settings a few years back,
> and it turned out to be more robust to configure ccache at the level of
> default system (well, container) compiler.
>
> One thing to check is whether default 5GB cache limit fits us well.  IIUC,
> flang builds are particularly big, and they may overflow the cache size.
>

Oh yeah, anything under 20GB is likely doomed, in particular if you share
the cache across configs (like one machine building gcc and clang).

Can you try to print cache statistics? Maybe tweak the job to clear the
stats before the job and print them after each build?


>
> --
> Maxim Kuvyrkov
> https://www.linaro.org
>
> > On 29 Jun 2022, at 16:33, David Spickett <david.spick...@linaro.org>
> wrote:
> >
> > While it's not visible in the zorg config we are using ccache. Except
> > we do it by setting the compiler to a script that runs the expected
> > clang/gcc via ccache. We can certainly look at using the ccache enable
> > in zorg instead (for the first attempt it was easier to do it in a way
> > we could control on our end).
> >
> > Looking at the our flang bots overall 2 hours seems to be the average
> > (out of tree is an outlier), I don't know anything about non Linaro
> > flang bots. We will check if there is some obvious bottleneck here but
> > we have resource constraints that limit how fast we can go even with
> > perfect caching. Are there any other bots you were interested in? We
> > can check those too.
> >
> > What build times were you expecting to see? It is useful for us to
> > know what expectations are even if, unfortunately, we don't meet them
> > at this time.
>

flang-x86_64-knl-linux seems to to average 15-20min here, which is more
like I would expect.

Even there they could go much faster: we could avoid building the world and
only build flang and the test dependencies. Right now the bottleneck is
linking all of the LLVM tools that aren't relevant for testing flang.

Compare with the way I set up the MLIR bots:
https://lab.llvm.org/buildbot/#/builders/61/builds/28582
The build step here is exclusively building the binaries needed for running
`check-mlir` and nothing more.

MLIR is smaller than flang, but we're still having a turnaround of 3-5 min
when the cache is hot.


-- 
Mehdi




> >
> > Thanks,
> > David Spickett.
> >
> >
> > On Tue, 28 Jun 2022 at 18:05, Mehdi AMINI <joker....@gmail.com> wrote:
> >>
> >> Hi,
> >>
> >> I noticed that bots like flang-aarch64-latest-gcc are quite slow and
> could
> >> benefit from enabling ccache. Could you make it available on the system
> so
> >> it could be turned on for all these builds?
> >>
> >> Thanks,
> >>
> >> --
> >> Mehdi
> >> _______________________________________________
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>
>
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