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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r14-1568] libstdc++: Also use sendfile for big files Date: Tue, 6 Jun 2023 11:35:52 +0000 (GMT) [thread overview] Message-ID: <20230606113552.A4B1C385802F@sourceware.org> (raw) https://gcc.gnu.org/g:f80a8b42296265bb868a48592a2bd1fdaa2a3d8a commit r14-1568-gf80a8b42296265bb868a48592a2bd1fdaa2a3d8a Author: Jannik Glückert <jannik.glueckert@gmail.com> Date: Mon Mar 6 20:52:08 2023 +0100 libstdc++: Also use sendfile for big files 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 libstdc++-v3/ChangeLog: * acinclude.m4 (_GLIBCXX_HAVE_LSEEK): Define. * config.h.in: Regenerate. * configure: Regenerate. * src/filesystem/ops-common.h (copy_file_sendfile): Define new function for sendfile logic. Loop to support large files. Skip zero-length files. (do_copy_file): Use it. Signed-off-by: Jannik Glückert <jannik.glueckert@gmail.com> Diff: --- libstdc++-v3/acinclude.m4 | 51 ++++++++----- libstdc++-v3/config.h.in | 3 + libstdc++-v3/configure | 127 ++++++++++++++++++++++--------- libstdc++-v3/src/filesystem/ops-common.h | 73 +++++++++++------- 4 files changed, 170 insertions(+), 84 deletions(-) diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4 index 6ae141b8c20..1920444e5cd 100644 --- a/libstdc++-v3/acinclude.m4 +++ b/libstdc++-v3/acinclude.m4 @@ -4956,6 +4956,7 @@ 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 @@ -5091,25 +5092,6 @@ dnl if test $glibcxx_cv_fchmodat = yes; then AC_DEFINE(_GLIBCXX_USE_FCHMODAT, 1, [Define if fchmodat is available in <sys/stat.h>.]) fi -dnl - AC_CACHE_CHECK([for sendfile that can copy files], - glibcxx_cv_sendfile, [dnl - case "${target_os}" in - gnu* | linux* | solaris* | uclinux*) - GCC_TRY_COMPILE_OR_LINK( - [#include <sys/sendfile.h>], - [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 <sys/sendfile.h>.]) - fi dnl AC_CACHE_CHECK([for link], glibcxx_cv_link, [dnl @@ -5122,6 +5104,18 @@ dnl if test $glibcxx_cv_link = yes; then AC_DEFINE(HAVE_LINK, 1, [Define if link is available in <unistd.h>.]) fi +dnl + AC_CACHE_CHECK([for lseek], + glibcxx_cv_lseek, [dnl + GCC_TRY_COMPILE_OR_LINK( + [#include <unistd.h>], + [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 <unistd.h>.]) + fi dnl AC_CACHE_CHECK([for readlink], glibcxx_cv_readlink, [dnl @@ -5158,6 +5152,25 @@ dnl if test $glibcxx_cv_truncate = yes; then AC_DEFINE(HAVE_TRUNCATE, 1, [Define if truncate is available in <unistd.h>.]) fi +dnl + AC_CACHE_CHECK([for sendfile that can copy files], + glibcxx_cv_sendfile, [dnl + case "${target_os}" in + gnu* | linux* | solaris* | uclinux*) + GCC_TRY_COMPILE_OR_LINK( + [#include <sys/sendfile.h>], + [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 <sys/sendfile.h>.]) + fi dnl AC_CACHE_CHECK([for fdopendir], glibcxx_cv_fdopendir, [dnl diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in index 5a95853cbbe..99ce682670e 100644 --- a/libstdc++-v3/config.h.in +++ b/libstdc++-v3/config.h.in @@ -254,6 +254,9 @@ /* Define to 1 if you have the `logl' function. */ #undef HAVE_LOGL +/* Define if lseek is available in <unistd.h>. */ +#undef HAVE_LSEEK + /* Define to 1 if you have the <machine/endian.h> header file. */ #undef HAVE_MACHINE_ENDIAN_H diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure index 70d169cf64b..50a7c30665b 100755 --- a/libstdc++-v3/configure +++ b/libstdc++-v3/configure @@ -71005,29 +71005,27 @@ $as_echo "$glibcxx_cv_fchmodat" >&6; } $as_echo "#define _GLIBCXX_USE_FCHMODAT 1" >>confdefs.h fi - { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sendfile that can copy files" >&5 -$as_echo_n "checking for sendfile that can copy files... " >&6; } -if ${glibcxx_cv_sendfile+:} false; then : + { $as_echo "$as_me:${as_lineno-$LINENO}: checking for link" >&5 +$as_echo_n "checking for link... " >&6; } +if ${glibcxx_cv_link+:} false; then : $as_echo_n "(cached) " >&6 else - case "${target_os}" in - gnu* | linux* | solaris* | uclinux*) - if test x$gcc_no_link = xyes; then + if test x$gcc_no_link = xyes; then cat confdefs.h - <<_ACEOF >conftest.$ac_ext /* end confdefs.h. */ -#include <sys/sendfile.h> +#include <unistd.h> int main () { -sendfile(1, 2, (off_t*)0, sizeof 1); +link("", ""); ; return 0; } _ACEOF if ac_fn_cxx_try_compile "$LINENO"; then : - glibcxx_cv_sendfile=yes + glibcxx_cv_link=yes else - glibcxx_cv_sendfile=no + glibcxx_cv_link=no fi rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext else @@ -71036,40 +71034,35 @@ else fi cat confdefs.h - <<_ACEOF >conftest.$ac_ext /* end confdefs.h. */ -#include <sys/sendfile.h> +#include <unistd.h> int main () { -sendfile(1, 2, (off_t*)0, sizeof 1); +link("", ""); ; return 0; } _ACEOF if ac_fn_cxx_try_link "$LINENO"; then : - glibcxx_cv_sendfile=yes + glibcxx_cv_link=yes else - glibcxx_cv_sendfile=no + glibcxx_cv_link=no fi rm -f core conftest.err conftest.$ac_objext \ conftest$ac_exeext conftest.$ac_ext fi - ;; - *) - glibcxx_cv_sendfile=no - ;; - esac fi -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_sendfile" >&5 -$as_echo "$glibcxx_cv_sendfile" >&6; } - if test $glibcxx_cv_sendfile = yes; then +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_link" >&5 +$as_echo "$glibcxx_cv_link" >&6; } + if test $glibcxx_cv_link = yes; then -$as_echo "#define _GLIBCXX_USE_SENDFILE 1" >>confdefs.h +$as_echo "#define HAVE_LINK 1" >>confdefs.h fi - { $as_echo "$as_me:${as_lineno-$LINENO}: checking for link" >&5 -$as_echo_n "checking for link... " >&6; } -if ${glibcxx_cv_link+:} false; then : + { $as_echo "$as_me:${as_lineno-$LINENO}: checking for lseek" >&5 +$as_echo_n "checking for lseek... " >&6; } +if ${glibcxx_cv_lseek+:} false; then : $as_echo_n "(cached) " >&6 else if test x$gcc_no_link = xyes; then @@ -71079,15 +71072,15 @@ else int main () { -link("", ""); +lseek(1, 0, SEEK_SET); ; return 0; } _ACEOF if ac_fn_cxx_try_compile "$LINENO"; then : - glibcxx_cv_link=yes + glibcxx_cv_lseek=yes else - glibcxx_cv_link=no + glibcxx_cv_lseek=no fi rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext else @@ -71100,26 +71093,26 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext int main () { -link("", ""); +lseek(1, 0, SEEK_SET); ; return 0; } _ACEOF if ac_fn_cxx_try_link "$LINENO"; then : - glibcxx_cv_link=yes + glibcxx_cv_lseek=yes else - glibcxx_cv_link=no + glibcxx_cv_lseek=no fi rm -f core conftest.err conftest.$ac_objext \ conftest$ac_exeext conftest.$ac_ext fi fi -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_link" >&5 -$as_echo "$glibcxx_cv_link" >&6; } - if test $glibcxx_cv_link = yes; then +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_lseek" >&5 +$as_echo "$glibcxx_cv_lseek" >&6; } + if test $glibcxx_cv_lseek = yes; then -$as_echo "#define HAVE_LINK 1" >>confdefs.h +$as_echo "#define HAVE_LSEEK 1" >>confdefs.h fi { $as_echo "$as_me:${as_lineno-$LINENO}: checking for readlink" >&5 @@ -71286,6 +71279,68 @@ $as_echo "$glibcxx_cv_truncate" >&6; } $as_echo "#define HAVE_TRUNCATE 1" >>confdefs.h + fi + { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sendfile that can copy files" >&5 +$as_echo_n "checking for sendfile that can copy files... " >&6; } +if ${glibcxx_cv_sendfile+:} false; then : + $as_echo_n "(cached) " >&6 +else + case "${target_os}" in + gnu* | linux* | solaris* | uclinux*) + if test x$gcc_no_link = xyes; then + cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ +#include <sys/sendfile.h> +int +main () +{ +sendfile(1, 2, (off_t*)0, sizeof 1); + ; + return 0; +} +_ACEOF +if ac_fn_cxx_try_compile "$LINENO"; then : + glibcxx_cv_sendfile=yes +else + glibcxx_cv_sendfile=no +fi +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext +else + if test x$gcc_no_link = xyes; then + as_fn_error $? "Link tests are not allowed after GCC_NO_EXECUTABLES." "$LINENO" 5 +fi +cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ +#include <sys/sendfile.h> +int +main () +{ +sendfile(1, 2, (off_t*)0, sizeof 1); + ; + return 0; +} +_ACEOF +if ac_fn_cxx_try_link "$LINENO"; then : + glibcxx_cv_sendfile=yes +else + glibcxx_cv_sendfile=no +fi +rm -f core conftest.err conftest.$ac_objext \ + conftest$ac_exeext conftest.$ac_ext +fi + ;; + *) + glibcxx_cv_sendfile=no + ;; + esac + +fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_sendfile" >&5 +$as_echo "$glibcxx_cv_sendfile" >&6; } + if test $glibcxx_cv_sendfile = yes && test $glibcxx_cv_lseek = yes; then + +$as_echo "#define _GLIBCXX_USE_SENDFILE 1" >>confdefs.h + fi { $as_echo "$as_me:${as_lineno-$LINENO}: checking for fdopendir" >&5 $as_echo_n "checking for fdopendir... " >&6; } diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h index c95511b5c95..36444388208 100644 --- a/libstdc++-v3/src/filesystem/ops-common.h +++ b/libstdc++-v3/src/filesystem/ops-common.h @@ -51,6 +51,7 @@ # include <ext/stdio_filebuf.h> # ifdef _GLIBCXX_USE_SENDFILE # include <sys/sendfile.h> // sendfile +# include <unistd.h> // lseek # endif #endif @@ -358,6 +359,34 @@ _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 = EINVAL; + return false; + } + size_t bytes_left = length; + off_t offset = 0; + ssize_t bytes_copied; + do + { + bytes_copied = ::sendfile(fd_out, fd_in, &offset, bytes_left); + bytes_left -= bytes_copied; + } + while (bytes_left > 0 && bytes_copied > 0); + if (bytes_copied < 0) + { + ::lseek(fd_out, 0, SEEK_SET); + return false; + } + return true; + } +#endif bool do_copy_file(const char_type* from, const char_type* to, std::filesystem::copy_options_existing_file options, @@ -498,16 +527,22 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM return false; } - size_t count = from_st->st_size; + bool has_copied = false; + #if defined _GLIBCXX_USE_SENDFILE && ! defined _GLIBCXX_FILESYSTEM_IS_WINDOWS - off_t offset = 0; - ssize_t n = ::sendfile(out.fd, in.fd, &offset, count); - if (n < 0 && errno != ENOSYS && errno != EINVAL) + if (!has_copied) + has_copied = copy_file_sendfile(in.fd, out.fd, from_st->st_size); + if (!has_copied) { - ec.assign(errno, std::generic_category()); - return false; + if (errno != ENOSYS && errno != EINVAL) + { + ec.assign(errno, std::generic_category()); + return false; + } } - if ((size_t)n == count) +#endif + + if (has_copied) { if (!out.close() || !in.close()) { @@ -517,9 +552,6 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM ec.clear(); return true; } - else if (n > 0) - count -= n; -#endif // _GLIBCXX_USE_SENDFILE using std::ios; __gnu_cxx::stdio_filebuf<char> sbin(in.fd, ios::in|ios::binary); @@ -530,29 +562,12 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM if (sbout.is_open()) out.fd = -1; -#ifdef _GLIBCXX_USE_SENDFILE - if (n != 0) - { - if (n < 0) - n = 0; - - const auto p1 = sbin.pubseekoff(n, ios::beg, ios::in); - const auto p2 = sbout.pubseekoff(n, ios::beg, ios::out); - - const std::streampos errpos(std::streamoff(-1)); - if (p1 == errpos || p2 == errpos) - { - ec = std::make_error_code(std::errc::io_error); - return false; - } - } -#endif - - if (count && !(std::ostream(&sbout) << &sbin)) + if (from_st->st_size && !(std::ostream(&sbout) << &sbin)) { ec = std::make_error_code(std::errc::io_error); return false; } + if (!sbout.close() || !sbin.close()) { ec.assign(errno, std::generic_category());
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