This iteration improves error handling for copy_file_range,
particularly around undocumented error codes in earlier kernel
versions.
Additionally this fixes the userspace copy fallback to handle
zero-length files such as in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108178.
Lastly, the case "src gets resized during the copy loop" is now
considered and will return true once the loop hits EOF (this is the
only situation, aside from a zero-length src, where sendfile and
copy_file_range return 0).
Best
Jannik
From b55eb8dccaa44f07d8acbe6294326a46c920b04f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jannik=20Gl=C3=BCckert?=
Date: Mon, 6 Mar 2023 20:52:08 +0100
Subject: [PATCH 1/2] libstdc++: also use sendfile for big files
MIME-Version: 1.0
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we were previously only using sendfile for files smaller than 2GB, as
sendfile needs to be called repeatedly for files bigger than that.
some quick numbers, copying a 16GB file, average of 10 repetitions:
old:
real: 13.4s
user: 0.14s
sys : 7.43s
new:
real: 8.90s
user: 0.00s
sys : 3.68s
Additionally, this fixes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108178
libstdc++-v3/ChangeLog:
* acinclude.m4 (_GLIBCXX_HAVE_LSEEK): define
* config.h.in: Regenerate.
* configure: Regenerate.
* src/filesystem/ops-common.h: enable sendfile for files
>2GB in std::filesystem::copy_file, skip zero-length files
Signed-off-by: Jannik Glückert
---
libstdc++-v3/acinclude.m4| 51 +
libstdc++-v3/config.h.in | 3 +
libstdc++-v3/configure | 127 ---
libstdc++-v3/src/filesystem/ops-common.h | 86 ---
4 files changed, 175 insertions(+), 92 deletions(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 5136c0571e8..85a09a5a869 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4583,6 +4583,7 @@ dnl _GLIBCXX_USE_FCHMOD
dnl _GLIBCXX_USE_FCHMODAT
dnl _GLIBCXX_USE_SENDFILE
dnl HAVE_LINK
+dnl HAVE_LSEEK
dnl HAVE_READLINK
dnl HAVE_SYMLINK
dnl
@@ -4718,25 +4719,6 @@ dnl
if test $glibcxx_cv_fchmodat = yes; then
AC_DEFINE(_GLIBCXX_USE_FCHMODAT, 1, [Define if fchmodat is available in .])
fi
-dnl
- AC_CACHE_CHECK([for sendfile that can copy files],
-glibcxx_cv_sendfile, [dnl
-case "${target_os}" in
- gnu* | linux* | solaris* | uclinux*)
- GCC_TRY_COMPILE_OR_LINK(
- [#include ],
- [sendfile(1, 2, (off_t*)0, sizeof 1);],
- [glibcxx_cv_sendfile=yes],
- [glibcxx_cv_sendfile=no])
- ;;
- *)
- glibcxx_cv_sendfile=no
- ;;
-esac
- ])
- if test $glibcxx_cv_sendfile = yes; then
-AC_DEFINE(_GLIBCXX_USE_SENDFILE, 1, [Define if sendfile is available in .])
- fi
dnl
AC_CACHE_CHECK([for link],
glibcxx_cv_link, [dnl
@@ -4749,6 +4731,18 @@ dnl
if test $glibcxx_cv_link = yes; then
AC_DEFINE(HAVE_LINK, 1, [Define if link is available in .])
fi
+dnl
+ AC_CACHE_CHECK([for lseek],
+glibcxx_cv_lseek, [dnl
+GCC_TRY_COMPILE_OR_LINK(
+ [#include ],
+ [lseek(1, 0, SEEK_SET);],
+ [glibcxx_cv_lseek=yes],
+ [glibcxx_cv_lseek=no])
+ ])
+ if test $glibcxx_cv_lseek = yes; then
+AC_DEFINE(HAVE_LSEEK, 1, [Define if lseek is available in .])
+ fi
dnl
AC_CACHE_CHECK([for readlink],
glibcxx_cv_readlink, [dnl
@@ -4785,6 +4779,25 @@ dnl
if test $glibcxx_cv_truncate = yes; then
AC_DEFINE(HAVE_TRUNCATE, 1, [Define if truncate is available in .])
fi
+dnl
+ AC_CACHE_CHECK([for sendfile that can copy files],
+glibcxx_cv_sendfile, [dnl
+case "${target_os}" in
+ gnu* | linux* | solaris* | uclinux*)
+ GCC_TRY_COMPILE_OR_LINK(
+ [#include ],
+ [sendfile(1, 2, (off_t*)0, sizeof 1);],
+ [glibcxx_cv_sendfile=yes],
+ [glibcxx_cv_sendfile=no])
+ ;;
+ *)
+ glibcxx_cv_sendfile=no
+ ;;
+esac
+ ])
+ if test $glibcxx_cv_sendfile = yes && test $glibcxx_cv_lseek = yes; then
+AC_DEFINE(_GLIBCXX_USE_SENDFILE, 1, [Define if sendfile is available in .])
+ fi
dnl
AC_CACHE_CHECK([for fdopendir],
glibcxx_cv_fdopendir, [dnl
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index abbfca43e5c..9e1b1d41dc5 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -51,6 +51,7 @@
# include
# ifdef _GLIBCXX_USE_SENDFILE
# include // sendfile
+# include // lseek
# endif
#endif
@@ -358,6 +359,32 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
}
#ifdef NEED_DO_COPY_FILE
+#if defined _GLIBCXX_USE_SENDFILE && ! defined _GLIBCXX_FILESYSTEM_IS_WINDOWS
+ bool
+ copy_file_sendfile(int fd_in, int fd_out, size_t length) noexcept
+ {
+// a zero-length file is either empty, or not copyable by this syscall
+// return early to avoid the syscall cost
+if (length == 0)
+ {
+errno
