From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Lo16L-0001CA-Kn for qemu-devel@nongnu.org; Sun, 29 Mar 2009 15:55:25 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Lo16G-0001Bi-7e for qemu-devel@nongnu.org; Sun, 29 Mar 2009 15:55:24 -0400 Received: from [199.232.76.173] (port=37842 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Lo16G-0001Bf-3O for qemu-devel@nongnu.org; Sun, 29 Mar 2009 15:55:20 -0400 Received: from verein.lst.de ([213.95.11.210]:56582) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_3DES_EDE_CBC_SHA1:24) (Exim 4.60) (envelope-from ) id 1Lo16F-0004wb-E6 for qemu-devel@nongnu.org; Sun, 29 Mar 2009 15:55:19 -0400 Received: from verein.lst.de (localhost [127.0.0.1]) by verein.lst.de (8.12.3/8.12.3/Debian-7.1) with ESMTP id n2TJtHIF001340 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO) for ; Sun, 29 Mar 2009 21:55:17 +0200 Received: (from hch@localhost) by verein.lst.de (8.12.3/8.12.3/Debian-6.6) id n2TJtHqM001338 for qemu-devel@nongnu.org; Sun, 29 Mar 2009 21:55:17 +0200 Date: Sun, 29 Mar 2009 21:55:17 +0200 From: Christoph Hellwig Message-ID: <20090329195517.GD1215@lst.de> References: <20090329195346.GA625@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090329195346.GA625@lst.de> Subject: [Qemu-devel] [PATCH 4/5] native preadv/pwritev support Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org This ties up the preadv/pwritev syscalls to qemu if they are declared in unistd.h. This is the case currently on at least NetBSD and OpenBSD and will hopefully soon be the case on Linux. Thanks to Blue Swirl and Gerd Hoffmann for the configure autodetection of preadv/pwritev. Signed-off-by: Christoph Hellwig Index: qemu/posix-aio-compat.c =================================================================== --- qemu.orig/posix-aio-compat.c 2009-03-29 21:51:17.540004569 +0200 +++ qemu/posix-aio-compat.c 2009-03-29 21:51:17.849130422 +0200 @@ -33,6 +33,12 @@ static int cur_threads = 0; static int idle_threads = 0; static TAILQ_HEAD(, qemu_paiocb) request_list; +#ifdef HAVE_PREADV +static int preadv_present = 1; +#else +static int preadv_present = 0; +#endif + static void die2(int err, const char *what) { fprintf(stderr, "%s failed: %s\n", what, strerror(err)); @@ -87,6 +93,36 @@ static size_t handle_aiocb_ioctl(struct return ret; } +#ifdef HAVE_PREADV + +static ssize_t +qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset) +{ + return preadv(fd, iov, nr_iov, offset); +} + +static ssize_t +qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset) +{ + return pwritev(fd, iov, nr_iov, offset); +} + +#else + +static ssize_t +qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset) +{ + return -ENOSYS; +} + +static ssize_t +qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset) +{ + return -ENOSYS; +} + +#endif + /* * Check if we need to copy the data in the aiocb into a new * properly aligned buffer. @@ -104,6 +140,29 @@ static int aiocb_needs_copy(struct qemu_ return 0; } +static size_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb) +{ + size_t offset = 0; + ssize_t len; + + do { + if (aiocb->aio_type == QEMU_PAIO_WRITE) + len = qemu_pwritev(aiocb->aio_fildes, + aiocb->aio_iov, + aiocb->aio_niov, + aiocb->aio_offset + offset); + else + len = qemu_preadv(aiocb->aio_fildes, + aiocb->aio_iov, + aiocb->aio_niov, + aiocb->aio_offset + offset); + } while (len == -1 && errno == EINTR); + + if (len == -1) + return -errno; + return len; +} + static size_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf) { size_t offset = 0; @@ -140,12 +199,34 @@ static size_t handle_aiocb_rw(struct qem size_t nbytes; char *buf; - if (!aiocb_needs_copy(aiocb) && aiocb->aio_niov == 1) { + if (!aiocb_needs_copy(aiocb)) { /* * If there is just a single buffer, and it is properly aligned * we can just use plain pread/pwrite without any problems. */ - return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base); + if (aiocb->aio_niov == 1) + return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base); + + /* + * We have more than one iovec, and all are properly aligned. + * + * Try preadv/pwritev first and fall back to linearizing the + * buffer if it's not supported. + */ + if (preadv_present) { + nbytes = handle_aiocb_rw_vector(aiocb); + if (nbytes == aiocb->aio_nbytes) + return nbytes; + if (nbytes < 0 && nbytes != -ENOSYS) + return nbytes; + preadv_present = 0; + } + + /* + * XXX(hch): short read/write. no easy way to handle the reminder + * using these interfaces. For now retry using plain + * pread/pwrite? + */ } /* Index: qemu/configure =================================================================== --- qemu.orig/configure 2009-03-29 21:47:22.357005638 +0200 +++ qemu/configure 2009-03-29 21:52:23.924005232 +0200 @@ -1095,6 +1095,19 @@ if $cc $ARCH_CFLAGS -o $TMPE $TMPC > /de fi ########################################## +# preadv probe +cat > $TMPC < +#include +#include +int main(void) { preadv; } +EOF +preadv=no +if $cc $ARCH_CFLAGS -o $TMPE $TMPC > /dev/null 2> /dev/null ; then + preadv=yes +fi + +########################################## # fdt probe if test "$fdt" = "yes" ; then fdt=no @@ -1207,6 +1220,7 @@ echo "AIO support $aio" echo "Install blobs $blobs" echo "KVM support $kvm" echo "fdt support $fdt" +echo "preadv support $preadv" if test $sdl_too_old = "yes"; then echo "-> Your SDL version is too old - please upgrade to have SDL support" @@ -1506,6 +1520,9 @@ fi if test "$iovec" = "yes" ; then echo "#define HAVE_IOVEC 1" >> $config_h fi +if test "$preadv" = "yes" ; then + echo "#define HAVE_PREADV 1" >> $config_h +fi if test "$fdt" = "yes" ; then echo "#define HAVE_FDT 1" >> $config_h echo "FDT_LIBS=-lfdt" >> $config_mak