[PATCH] (Re: Splitting up 27_io/basic_istream/ignore/wchar_t/94749.cc (takes too long))

[Hans-Peter Nilsson <hp@axis.com>]

Thank you for your consideration.  (Or is that phrase only used negatively?)

> From: Jonathan Wakely <jwakely@redhat.com>
> Date: Fri, 9 Jun 2023 21:40:15 +0100

> test01, test02, test03 and test04 should run almost instantly. On my system
> they take about 5 microseconds each. So I don't think splitting those up
> will help.

Right.

> I thought it would help to avoid re-allocating the buffer and zeroing it
> again. If we reuse the same buffer, then we just have to loop until we
> overflow the 32-bit counter. That would make the whole test run much
> faster, which would reduce the total time for a testsuite run. Splitting
> the file up into smaller files would not decrease the total time, only
> decrease the time for that single test so it doesn't time out.
> 
> I've attached a patch that does that. I makes very little difference for
> me, probably because allocating zero-filled pages isn't actually expensive
> on linux. Maybe it will make a differene for your simulator though?

Nope, just some five seconds down (from about 10min 21s).

> You could also try reducing the size of the buffer:
> +#ifdef SIMULATOR_TEST
> +  static const streamsize bufsz = 16 << limits::digits10;
> +#else
>   static const streamsize bufsz = 2048 << limits::digits10;
> +#endif

Was that supposed to be with or without the patch?  Anyway;
both: 606s.  Only smaller bufsz: 614s.  (All numbers subject
to usual system jitter.)

> test06 is the really slow part, that takes 10+ seconds for me. But that
> entire function should already be skipped for simulators.

Yep, we may have been here before...  I certainly get a
deja-vu feeling here, but visiting old email conversations
of ours, it seems I easily conflate several similar ones.
I see that here, test06 was always #ifndef SIMULATOR_TEST.

> We can probably skip test05 for simulators too, none of the code it tests
> is platform-specific, so as long as it's being tested on x86 we don't
> really need to test it on cris-elf too.

Thanks.  Let's do that, then.  The similar s/wchar_t/char/
test clocks in at "only" 3m30s, but I suggest treating it
the same, if nothing else than for symmetry.

Ok as below?

-- >8 --
Subject: [PATCH] testsuite: Cut down 27_io/basic_istream/.../94749.cc for
 simulators

The test wchar_t/94749.cc can take about 10 minutes on some
simulator/host combinations with char/94749.cc at a third of
that time.  The cause is test05 which is quite heavy and
includes wrapping a 32-bit counter.  Run it only for native
setups.

	* testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc (main)
	[! SIMULATOR_TEST]: Also exclude running test05.
	* testsuite/27_io/basic_istream/ignore/char/94749.cc: Ditto.
---
 libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/94749.cc | 2 +-
 .../testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/94749.cc b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/94749.cc
index 6416863983b7..9160995c05ec 100644
--- a/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/94749.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/94749.cc
@@ -221,8 +221,8 @@ main()
   test02();
   test03();
   test04();
-  test05();
 #ifndef SIMULATOR_TEST
+  test05();
   test06();
 #endif
 }
diff --git a/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc
index 65e0a326c109..a5b9eb71a389 100644
--- a/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/94749.cc
@@ -221,8 +221,8 @@ main()
   test02();
   test03();
   test04();
-  test05();
 #ifndef SIMULATOR_TEST
+  test05();
   test06();
 #endif
 }
-- 
2.30.2