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bh=vfkl4rJMoX4v/Kru1ixqosWtzfnZu4p/EcgbmkHIoEo=; b=CIWqX8/7211SEYEpXRhnUWxCv9wy2zdyrP71bu98w6t835K/zVGE/x5TL3bbiTfOqBbqty 7QtePh7eJZRunaq9omald09ub25yapu473kWM9bNMCoqYsOP3q1hT9RHhrs1lcMJ1kkZUB qIwAiqRG7Slj10mbwFd2B5J4pHY03UA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1724857021; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vfkl4rJMoX4v/Kru1ixqosWtzfnZu4p/EcgbmkHIoEo=; b=6o0Lzt2lteYOr+YgPYgH/6yW5p/eNlrxc4E0IM/tSisr8bs9z9dwXMEVOPAGiHgaWuXnic gO5b2TNBbKdtBGCg== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PATCH v7 4/4] migration/multifd: Add documentation for multifd methods Date: Wed, 28 Aug 2024 11:56:50 -0300 Message-Id: <20240828145650.15879-5-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20240828145650.15879-1-farosas@suse.de> References: <20240828145650.15879-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spamd-Result: default: False [-2.80 / 50.00]; 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charset="utf-8" Add documentation clarifying the usage of the multifd methods. The general idea is that the client code calls into multifd to trigger send/recv of data and multifd then calls these hooks back from the worker threads at opportune moments so the client can process a portion of the data. Suggested-by: Peter Xu Signed-off-by: Fabiano Rosas Reviewed-by: Peter Xu --- migration/multifd.h | 76 +++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 70 insertions(+), 6 deletions(-) diff --git a/migration/multifd.h b/migration/multifd.h index 13e7a88c01..3bb96e9558 100644 --- a/migration/multifd.h +++ b/migration/multifd.h @@ -229,17 +229,81 @@ typedef struct { } MultiFDRecvParams; =20 typedef struct { - /* Setup for sending side */ + /* + * The send_setup, send_cleanup, send_prepare are only called on + * the QEMU instance at the migration source. + */ + + /* + * Setup for sending side. Called once per channel during channel + * setup phase. + * + * Must allocate p->iov. If packets are in use (default), one + * extra iovec must be allocated for the packet header. Any memory + * allocated in this hook must be released at send_cleanup. + * + * p->write_flags may be used for passing flags to the QIOChannel. + * + * p->compression_data may be used by compression methods to store + * compression data. + */ int (*send_setup)(MultiFDSendParams *p, Error **errp); - /* Cleanup for sending side */ + + /* + * Cleanup for sending side. Called once per channel during + * channel cleanup phase. + */ void (*send_cleanup)(MultiFDSendParams *p, Error **errp); - /* Prepare the send packet */ + + /* + * Prepare the send packet. Called as a result of multifd_send() + * on the client side, with p pointing to the MultiFDSendParams of + * a channel that is currently idle. + * + * Must populate p->iov with the data to be sent, increment + * p->iovs_num to match the amount of iovecs used and set + * p->next_packet_size with the amount of data currently present + * in p->iov. + * + * Must indicate whether this is a compression packet by setting + * p->flags. + * + * As a last step, if packets are in use (default), must prepare + * the packet by calling multifd_send_fill_packet(). + */ int (*send_prepare)(MultiFDSendParams *p, Error **errp); - /* Setup for receiving side */ + + /* + * The recv_setup, recv_cleanup, recv are only called on the QEMU + * instance at the migration destination. + */ + + /* + * Setup for receiving side. Called once per channel during + * channel setup phase. May be empty. + * + * May allocate data structures for the receiving of data. May use + * p->iov. Compression methods may use p->compress_data. + */ int (*recv_setup)(MultiFDRecvParams *p, Error **errp); - /* Cleanup for receiving side */ + + /* + * Cleanup for receiving side. Called once per channel during + * channel cleanup phase. May be empty. + */ void (*recv_cleanup)(MultiFDRecvParams *p); - /* Read all data */ + + /* + * Data receive method. Called as a result of multifd_recv() on + * the client side, with p pointing to the MultiFDRecvParams of a + * channel that is currently idle. Only called if there is data + * available to receive. + * + * Must validate p->flags according to what was set at + * send_prepare. + * + * Must read the data from the QIOChannel p->c. + */ int (*recv)(MultiFDRecvParams *p, Error **errp); } MultiFDMethods; =20 --=20 2.35.3