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Thu, 5 May 2022 08:05:43 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.128]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6A9C614A4FAD; Thu, 5 May 2022 08:05:41 +0000 (UTC) Date: Thu, 5 May 2022 09:05:38 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Leonardo Bras Cc: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini , Elena Ufimtseva , Jagannathan Raman , John G Johnson , Juan Quintela , "Dr. David Alan Gilbert" , Eric Blake , Markus Armbruster , Fam Zheng , Peter Xu , qemu-devel@nongnu.org, qemu-block@nongnu.org Subject: Re: [PATCH v11 2/7] QIOChannelSocket: Implement io_writev zero copy flag & io_flush for CONFIG_LINUX Message-ID: References: <20220504191835.791580-1-leobras@redhat.com> <20220504191835.791580-3-leobras@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220504191835.791580-3-leobras@redhat.com> User-Agent: Mutt/2.1.5 (2021-12-30) X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 Received-SPF: pass client-ip=170.10.133.74; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-74.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, May 04, 2022 at 04:18:31PM -0300, Leonardo Bras wrote: > For CONFIG_LINUX, implement the new zero copy flag and the optional callback > io_flush on QIOChannelSocket, but enables it only when MSG_ZEROCOPY > feature is available in the host kernel, which is checked on > qio_channel_socket_connect_sync() > > qio_channel_socket_flush() was implemented by counting how many times > sendmsg(...,MSG_ZEROCOPY) was successfully called, and then reading the > socket's error queue, in order to find how many of them finished sending. > Flush will loop until those counters are the same, or until some error occurs. > > Notes on using writev() with QIO_CHANNEL_WRITE_FLAG_ZERO_COPY: > 1: Buffer > - As MSG_ZEROCOPY tells the kernel to use the same user buffer to avoid copying, > some caution is necessary to avoid overwriting any buffer before it's sent. > If something like this happen, a newer version of the buffer may be sent instead. > - If this is a problem, it's recommended to call qio_channel_flush() before freeing > or re-using the buffer. > > 2: Locked memory > - When using MSG_ZERCOCOPY, the buffer memory will be locked after queued, and > unlocked after it's sent. > - Depending on the size of each buffer, and how often it's sent, it may require > a larger amount of locked memory than usually available to non-root user. > - If the required amount of locked memory is not available, writev_zero_copy > will return an error, which can abort an operation like migration, > - Because of this, when an user code wants to add zero copy as a feature, it > requires a mechanism to disable it, so it can still be accessible to less > privileged users. > > Signed-off-by: Leonardo Bras > Reviewed-by: Peter Xu > Reviewed-by: Daniel P. Berrangé > Reviewed-by: Juan Quintela > --- > include/io/channel-socket.h | 2 + > io/channel-socket.c | 120 ++++++++++++++++++++++++++++++++++-- > 2 files changed, 118 insertions(+), 4 deletions(-) > > diff --git a/include/io/channel-socket.h b/include/io/channel-socket.h > index e747e63514..513c428fe4 100644 > --- a/include/io/channel-socket.h > +++ b/include/io/channel-socket.h > @@ -47,6 +47,8 @@ struct QIOChannelSocket { > socklen_t localAddrLen; > struct sockaddr_storage remoteAddr; > socklen_t remoteAddrLen; > + ssize_t zero_copy_queued; > + ssize_t zero_copy_sent; > }; > > > diff --git a/io/channel-socket.c b/io/channel-socket.c > index 696a04dc9c..ae756ce166 100644 > --- a/io/channel-socket.c > +++ b/io/channel-socket.c > @@ -25,9 +25,25 @@ > #include "io/channel-watch.h" > #include "trace.h" > #include "qapi/clone-visitor.h" > +#ifdef CONFIG_LINUX > +#include > +#include > +#endif > > #define SOCKET_MAX_FDS 16 > > +/* > + * Zero-copy defines bellow are included to avoid breaking builds on systems > + * that don't support MSG_ZEROCOPY, while keeping the functions more readable > + * (without a lot of ifdefs). > + */ > +#ifndef MSG_ZEROCOPY > +#define MSG_ZEROCOPY 0x4000000 > +#endif > +#ifndef SO_ZEROCOPY > +#define SO_ZEROCOPY 60 > +#endif Please put these behind CONFIG_LINUX to make it clear to readers that this is entirely Linux specific > + > SocketAddress * > qio_channel_socket_get_local_address(QIOChannelSocket *ioc, > Error **errp) > @@ -54,6 +70,8 @@ qio_channel_socket_new(void) > > sioc = QIO_CHANNEL_SOCKET(object_new(TYPE_QIO_CHANNEL_SOCKET)); > sioc->fd = -1; > + sioc->zero_copy_queued = 0; > + sioc->zero_copy_sent = 0; > > ioc = QIO_CHANNEL(sioc); > qio_channel_set_feature(ioc, QIO_CHANNEL_FEATURE_SHUTDOWN); > @@ -153,6 +171,16 @@ int qio_channel_socket_connect_sync(QIOChannelSocket *ioc, > return -1; > } > > +#ifdef CONFIG_LINUX > + int ret, v = 1; > + ret = setsockopt(fd, SOL_SOCKET, SO_ZEROCOPY, &v, sizeof(v)); > + if (ret == 0) { > + /* Zero copy available on host */ > + qio_channel_set_feature(QIO_CHANNEL(ioc), > + QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY); > + } > +#endif > + > return 0; > } > > @@ -533,6 +561,7 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc, > char control[CMSG_SPACE(sizeof(int) * SOCKET_MAX_FDS)]; > size_t fdsize = sizeof(int) * nfds; > struct cmsghdr *cmsg; > + int sflags = 0; > > memset(control, 0, CMSG_SPACE(sizeof(int) * SOCKET_MAX_FDS)); > > @@ -557,15 +586,27 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc, > memcpy(CMSG_DATA(cmsg), fds, fdsize); > } > > + if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) { > + sflags = MSG_ZEROCOPY; > + } Also should be behind CONFIG_LINUX > + > retry: > - ret = sendmsg(sioc->fd, &msg, 0); > + ret = sendmsg(sioc->fd, &msg, sflags); > if (ret <= 0) { > - if (errno == EAGAIN) { > + switch (errno) { > + case EAGAIN: > return QIO_CHANNEL_ERR_BLOCK; > - } > - if (errno == EINTR) { > + case EINTR: > goto retry; > + case ENOBUFS: > + if (sflags & MSG_ZEROCOPY) { > + error_setg_errno(errp, errno, > + "Process can't lock enough memory for using MSG_ZEROCOPY"); > + return -1; > + } > + break; And this ENOBUGS case behind CONFIG_LINUX > } > + > error_setg_errno(errp, errno, > "Unable to write to socket"); > return -1; > @@ -659,6 +700,74 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc, > } > #endif /* WIN32 */ > > + > +#ifdef CONFIG_LINUX > +static int qio_channel_socket_flush(QIOChannel *ioc, > + Error **errp) > +{ > + QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc); > + struct msghdr msg = {}; > + struct sock_extended_err *serr; > + struct cmsghdr *cm; > + char control[CMSG_SPACE(sizeof(*serr))]; > + int received; > + int ret = 1; > + > + msg.msg_control = control; > + msg.msg_controllen = sizeof(control); > + memset(control, 0, sizeof(control)); > + > + while (sioc->zero_copy_sent < sioc->zero_copy_queued) { > + received = recvmsg(sioc->fd, &msg, MSG_ERRQUEUE); > + if (received < 0) { > + switch (errno) { > + case EAGAIN: > + /* Nothing on errqueue, wait until something is available */ > + qio_channel_wait(ioc, G_IO_ERR); > + continue; > + case EINTR: > + continue; > + default: > + error_setg_errno(errp, errno, > + "Unable to read errqueue"); > + return -1; > + } > + } > + > + cm = CMSG_FIRSTHDR(&msg); > + if (cm->cmsg_level != SOL_IP && > + cm->cmsg_type != IP_RECVERR) { > + error_setg_errno(errp, EPROTOTYPE, > + "Wrong cmsg in errqueue"); > + return -1; > + } > + > + serr = (void *) CMSG_DATA(cm); > + if (serr->ee_errno != SO_EE_ORIGIN_NONE) { > + error_setg_errno(errp, serr->ee_errno, > + "Error on socket"); > + return -1; > + } > + if (serr->ee_origin != SO_EE_ORIGIN_ZEROCOPY) { > + error_setg_errno(errp, serr->ee_origin, > + "Error not from zero copy"); > + return -1; > + } > + > + /* No errors, count successfully finished sendmsg()*/ > + sioc->zero_copy_sent += serr->ee_data - serr->ee_info + 1; > + > + /* If any sendmsg() succeeded using zero copy, return 0 at the end */ > + if (serr->ee_code != SO_EE_CODE_ZEROCOPY_COPIED) { > + ret = 0; > + } > + } > + > + return ret; > +} > + > +#endif /* CONFIG_LINUX */ > + > static int > qio_channel_socket_set_blocking(QIOChannel *ioc, > bool enabled, > @@ -789,6 +898,9 @@ static void qio_channel_socket_class_init(ObjectClass *klass, > ioc_klass->io_set_delay = qio_channel_socket_set_delay; > ioc_klass->io_create_watch = qio_channel_socket_create_watch; > ioc_klass->io_set_aio_fd_handler = qio_channel_socket_set_aio_fd_handler; > +#ifdef CONFIG_LINUX > + ioc_klass->io_flush = qio_channel_socket_flush; > +#endif > } > > static const TypeInfo qio_channel_socket_info = { > -- > 2.36.0 > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|