[PATCH v2] Consolidate Linux readahead() implementations
Yury Norov
ynorov@caviumnetworks.com
Mon Sep 26 22:27:00 GMT 2016
On Mon, Sep 26, 2016 at 02:14:29PM -0700, Adhemerval Zanella wrote:
> Hi some comments below.
>
> On 25/09/2016 04:37, Yury Norov wrote:
> > There are 4 different implementations of readahead() in glibc:
> > - arm and mips32 use one located under sysdeps/unix/sysv/linux/arm;
> > - powerpc32 and wordsize64 has 2 another implementations in their
> > syscalls.list;
> > - and there's generic implementation under sysdeps/unix/sysv/linux for
> > other ports.
> >
> > With the [1] it's possible to consolidate all of them except tile32
> > under sysdeps/unix/sysv/linux. Tile32 like other 32-bit ports passes
> > offset in a pair of registers, but doesn't need register alignment,
> > though has __ASSUME_ALIGNED_REGISTER_PAIRS enabled. So it should be
> > handled as exception.
> >
> > [1] https://sourceware.org/ml/libc-alpha/2016-09/msg00452.html
> >
> > v2:
> > - remove powerpc and wordsize64 implementations;
> > - remove __ASSUME_READAHEAD_ALIGN option;
> > - add exception for tile32.
> > v1: https://sourceware.org/ml/libc-alpha/2016-09/msg00469.html
> >
> > 2016-09-25: Yury Norov <ynorov@caviumnetworks.com>
> >
> > * sysdeps/unix/sysv/linux/mips/mips32/readahead.c: Delete.
> > * sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list: Delete
> > readahead generation.
> > * sysdeps/unix/sysv/linux/wordsize-64/syscalls.list: Likewise.
> > * sysdeps/unix/sysv/linux/readahead.c: Consolidate implementation.
> > * sysdeps/unix/sysv/linux/tile/readahead.c: New file for
> > exceptional readahead() implementation.
> >
> > Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
> > CC: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> > CC: Florian Weimer <fw@deneb.enyo.de>
> > ---
> > sysdeps/unix/sysv/linux/arm/readahead.c | 37 ----------------------
> > sysdeps/unix/sysv/linux/mips/mips32/readahead.c | 1 -
> > .../sysv/linux/powerpc/powerpc32/syscalls.list | 3 --
> > sysdeps/unix/sysv/linux/readahead.c | 6 ++--
> > sysdeps/unix/sysv/linux/tile/readahead.c | 26 +++++++++++++++
> > sysdeps/unix/sysv/linux/wordsize-64/syscalls.list | 1 -
> > 6 files changed, 28 insertions(+), 46 deletions(-)
> > delete mode 100644 sysdeps/unix/sysv/linux/arm/readahead.c
> > delete mode 100644 sysdeps/unix/sysv/linux/mips/mips32/readahead.c
> > create mode 100644 sysdeps/unix/sysv/linux/tile/readahead.c
> >
> > diff --git a/sysdeps/unix/sysv/linux/arm/readahead.c b/sysdeps/unix/sysv/linux/arm/readahead.c
> > deleted file mode 100644
> > index 9824e6f..0000000
> > --- a/sysdeps/unix/sysv/linux/arm/readahead.c
> > +++ /dev/null
> > @@ -1,37 +0,0 @@
> > -/* Provide kernel hint to read ahead.
> > - Copyright (C) 2002-2016 Free Software Foundation, Inc.
> > - This file is part of the GNU C Library.
> > -
> > - The GNU C Library is free software; you can redistribute it and/or
> > - modify it under the terms of the GNU Lesser General Public
> > - License as published by the Free Software Foundation; either
> > - version 2.1 of the License, or (at your option) any later version.
> > -
> > - The GNU C Library is distributed in the hope that it will be useful,
> > - but WITHOUT ANY WARRANTY; without even the implied warranty of
> > - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > - Lesser General Public License for more details.
> > -
> > - You should have received a copy of the GNU Lesser General Public
> > - License along with the GNU C Library. If not, see
> > - <http://www.gnu.org/licenses/>. */
> > -
> > -#include <errno.h>
> > -#include <fcntl.h>
> > -#include <sys/types.h>
> > -#include <endian.h>
> > -
> > -#include <sysdep.h>
> > -#include <sys/syscall.h>
> > -
> > -
> > -ssize_t
> > -__readahead (int fd, off64_t offset, size_t count)
> > -{
> > - return INLINE_SYSCALL (readahead, 5, fd, 0,
> > - __LONG_LONG_PAIR ((off_t) (offset >> 32),
> > - (off_t) (offset & 0xffffffff)),
> > - count);
> > -}
> > -
> > -weak_alias (__readahead, readahead)
> > diff --git a/sysdeps/unix/sysv/linux/mips/mips32/readahead.c b/sysdeps/unix/sysv/linux/mips/mips32/readahead.c
> > deleted file mode 100644
> > index 80170c3..0000000
> > --- a/sysdeps/unix/sysv/linux/mips/mips32/readahead.c
> > +++ /dev/null
> > @@ -1 +0,0 @@
> > -#include <sysdeps/unix/sysv/linux/arm/readahead.c>
> > diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list b/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list
> > index 451d508..487bdd0 100644
> > --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list
> > +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list
> > @@ -7,8 +7,5 @@ lchown - lchown i:sii __lchown lchown@@GLIBC_2.0 chown@GLIBC_2.0
> > oldgetrlimit EXTRA getrlimit i:ip __old_getrlimit getrlimit@GLIBC_2.0
> > setrlimit - setrlimit i:ip __setrlimit setrlimit@GLIBC_2.0 setrlimit@@GLIBC_2.2
> >
> > -# Due to 64bit alignment there is a dummy second parameter
> > -readahead - readahead i:iiiii __readahead readahead
> > -
> > prlimit64 EXTRA prlimit64 i:iipp prlimit64
> > fanotify_mark EXTRA fanotify_mark i:iiiiis fanotify_mark
> > diff --git a/sysdeps/unix/sysv/linux/readahead.c b/sysdeps/unix/sysv/linux/readahead.c
> > index 92e5428..ced289b 100644
> > --- a/sysdeps/unix/sysv/linux/readahead.c
> > +++ b/sysdeps/unix/sysv/linux/readahead.c
> > @@ -29,10 +29,8 @@
> > ssize_t
> > __readahead (int fd, off64_t offset, size_t count)
> > {
> > - return INLINE_SYSCALL (readahead, 4, fd,
> > - __LONG_LONG_PAIR ((off_t) (offset >> 32),
> > - (off_t) (offset & 0xffffffff)),
> > - count);
> > + return INLINE_SYSCALL_CALL (readahead, fd, __ALIGNMENT_ARG
> > + SYSCALL_LL64 (offset), count);
> > }
> > #else
> > ssize_t
> > diff --git a/sysdeps/unix/sysv/linux/tile/readahead.c b/sysdeps/unix/sysv/linux/tile/readahead.c
> > new file mode 100644
> > index 0000000..05d7822
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/tile/readahead.c
> > @@ -0,0 +1,26 @@
> > +/* Provide kernel hint to read ahead.
> > + Copyright (C) 2002-2016 Free Software Foundation, Inc.
> > + This file is part of the GNU C Library.
> > +
> > + The GNU C Library is free software; you can redistribute it and/or
> > + modify it under the terms of the GNU Lesser General Public
> > + License as published by the Free Software Foundation; either
> > + version 2.1 of the License, or (at your option) any later version.
> > +
> > + The GNU C Library is distributed in the hope that it will be useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + Lesser General Public License for more details.
> > +
> > + You should have received a copy of the GNU Lesser General Public
> > + License along with the GNU C Library; if not, see
> > + <http://www.gnu.org/licenses/>. */
> > +
> > +#include <sysdep.h>
> > +
> > +#ifndef _LP64
> > +# undef __ALIGNMENT_ARG
> > +# define __ALIGNMENT_ARG
> > +#endif
> > +
> > +#include <sysdeps/unix/sysv/linux/readahead.c>
>
> I think my assumption where one can safely redefine __ALIGNMENT_ARG seems
> to be wrong. It due sysdep.h headers are included multiple times and
> without guards, so building for tile I am seeing:
>
> In file included from ../sysdeps/unix/sysv/linux/generic/sysdep.h:22:0,
> from ../sysdeps/unix/sysv/linux/tile/sysdep.h:21,
> from ../sysdeps/unix/sysv/linux/readahead.c:23,
> from ../sysdeps/unix/sysv/linux/tile/readahead.c:26:
> ../sysdeps/unix/sysv/linux/sysdep.h:33:0: warning: "__ALIGNMENT_ARG" redefined
> #define __ALIGNMENT_ARG 0,
> ^
> ../sysdeps/unix/sysv/linux/tile/readahead.c:23:0: note: this is the location of the previous definition
> # define __ALIGNMENT_ARG
>
> Based on this your first approach for using __ASSUME seems the most
> straightforward solution (sorry for the noise).
>
Ok, I'll send v3 with __ASSUME_READAHEAD_NO_ALIGN option.
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