The need for this emerged in:
https://bugs.python.org/issue36610#msg343948.
We currently use sendfile(2) syscall in high-level shutil.copyfile() on Linux and socket.sendfile() on UNIX. In addition this PR also tests shutil.copyfile() implementation on OSX which takes advantage of fcopyfile(2) syscall. The goal is to make sure "fast-copy" syscalls can handle files > 2G. On my Ubuntu 18.04 with SSD disk this introduces a 5 secs slowdown to the test run.

According to:
https://github.com/golang/go/issues/13892
...problems may arise on SunOS, so if a BB will turn red this is expected.

New changeset 5bcc6d89bcb622a6786fff632fabdcaf67dbb4e2 by Giampaolo Rodola in branch 'master':
bpo-37096: Add large-file tests for modules using sendfile(2) (GH-13676)
https://github.com/python/cpython/commit/5bcc6d89bcb622a6786fff632fabdcaf67dbb4e2

TestCopyfile fails on 32-bit system: bpo-38319.

After this change I get some disk space issues on the Fedora rawhide buildbot for the clang installed build only (and strangely enough not for the other jobs). There are currently around 9GB of free space there:

https://buildbot.python.org/all/#/builders/188/builds/1110

======================================================================
ERROR: test_tofromfile (test.test_array.DoubleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-rawhide-x86_64.clang-installed/build/target/lib/python3.9/test/test_array.py",
line 374, in test_tofromfile
    f.close()
OSError: [Errno 28] No space left on device

Sorry about that. I'm attaching a patch which skips those tests if there's not enough free disk space. If you confirm it works I'll make a PR.

Should we decorate the new files with @requires('largefile', '...')? Documentation:

    largefile - It is okay to run some test that may create huge
                files.  These tests can take a long time and may
                consume >2 GiB of disk space temporarily.

It may be interesting to add an option to regrtest to specify how much space can be used by tests, an option similar to -M/--memlimit which is for memory.

I don't recall if largefile is enabled by default on buildbots or not :-p

It seems that the -uall argument is passed to regrtest invocation for the buildbot run [0] which invokes the largefile tests (including all the resource intensive tests). However when configure is run you can see: checking whether to enable large file support... no

[0] https://github.com/python/cpython/blob/master/Lib/test/libregrtest/cmdline.py#L81

> checking whether to enable large file support... no

That's only at the C level to decide how to pass a file position.

It's unrelated to the regrtest "largefile" resource.

Alright added some more disk space at the buildbots, however it seems that it is not related to that. The current Fedora rawhide buildbot has 19GB of free space and the test is still failing.

I tested on the Fedora stable buildbot for which I reduced intentionally the free disk space to 14GB and it passed: https://buildbot.python.org/all/#/builders/233/builds/398

So something else might be at play here.

It seems that the test actually requires >4GB disk space, because it's copying a 2GB file from one place to another.

Also, it's using a temporary directory. On Fedora /tmp is memory-backed by default, it doesn't use regular disk space.

The test passes with a 8GB /tmp, but not a 6GB one.

That could suggest the test needs 3*2GB disk space for temporary files, plus something extra.

Can we reopen the issue?

Clearly this change modifies the expectations of free disk space for the temp files created by the tests.

Or at least clarify that those tests require more than 6gb of free disk space in /tmp for unix

Right now, "AMD64 Fedora Rawhide Clang 3.x" worker is broken: "C compiler cannot create executables"
https://bugs.python.org/issue39398

I close the issue. The test was fixed in bpo-39488:

commit b39fb8e847ac59b539ad7e93df91c1709815180e
Author: Giampaolo Rodola <g.rodola@gmail.com>
Date:   Wed Feb 5 18:20:52 2020 +0100

    bpo-39488: Skip test_largefile tests if not enough disk space (GH-18261)