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When these packages are released as part of Go 1.18,
Go 1.16 will no longer be supported, so we can remove
the +build tags in these files.
Ran go fix -fix=buildtag std cmd and then reverted the bootstrapDirs
as defined in src/cmd/dist/buildtool.go, which need to continue
to build with Go 1.4 for now.
Also reverted src/vendor and src/cmd/vendor, which will need
to be updated in their own repos first.
Manual changes in runtime/pprof/mprof_test.go to adjust line numbers.
For #41184.
Change-Id: Ic0f93f7091295b6abc76ed5cd6e6746e1280861e
Reviewed-on: https://go-review.googlesource.com/c/go/+/344955
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
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Linux 4.5 introduced (and Linux 5.3 refined) the copy_file_range
system call, which allows file systems the opportunity to implement
copy acceleration techniques. This commit adds support for
copy_file_range(2) to the os package.
Introduce a new ReadFrom method on *os.File, which makes *os.File
implement the io.ReaderFrom interface. If dst and src are both files,
this enables io.Copy(dst, src) to call dst.ReadFrom(src), which, in
turn, will call copy_file_range(2) if possible. If copy_file_range(2)
is not supported by the host kernel, or if either of dst or src
refers to a non-regular file, ReadFrom falls back to the regular
io.Copy code path.
Add internal/poll.CopyFileRange, which acquires locks on the
appropriate poll.FDs and performs the actual work, as well as
internal/syscall/unix.CopyFileRange, which wraps the copy_file_range
system call itself at the lowest level.
Rework file layout in internal/syscall/unix to accomodate the
additional system call numbers needed for copy_file_range.
Merge these definitions with the ones used by getrandom(2) into
sysnum_linux_$GOARCH.go files.
A note on additional optimizations: if dst and src both refer to pipes
in the invocation dst.ReadFrom(src), we could, in theory, use the
existing splice(2) code in package internal/poll to splice directly
from src to dst. Attempting this runs into trouble with the poller,
however. If we call splice(src, dst) and see EAGAIN, we cannot know
if it came from src not being ready for reading or dst not being
ready for writing. The write end of src and the read end of dst are
not under our control, so we cannot reliably use the poller to wait
for readiness. Therefore, it seems infeasible to use the new ReadFrom
method to splice between pipes directly. In conclusion, for now, the
only optimization enabled by the new ReadFrom method on *os.File is
the copy_file_range optimization.
Fixes #36817.
Change-Id: I696372639fa0cdf704e3f65414f7321fc7d30adb
Reviewed-on: https://go-review.googlesource.com/c/go/+/229101
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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