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bh=QCMu/h0Uagcfb4ObsHyaNRe66JC3h0/VZ/U7Orz2xOU=; b=i+7kKx3ckhTOhNzCHix+P/Q8v2shZJKPNqhrif8/bGDFbM6iTz1iInWfZWGKYK21Uca0MU ySc29LaTFtim5jL65oGaRgGPT4aiyOL0AjX8xm4G2ieZWG8JM1QzSNsGFUVYiaYKw7Cm/m smIwLFYkyXSMwQZgNCyqui3okDt9IQk= X-MC-Unique: hZP7jx5fNCCqUNBLQ28FHw-1 From: peterx@redhat.com To: qemu-devel@nongnu.org Cc: Hao Xiang , Bryan Zhang , Fabiano Rosas , peterx@redhat.com, Avihai Horon , Yuan Liu , Prasad Pandit Subject: [PATCH v2 18/23] migration/multifd: Rewrite multifd_queue_page() Date: Fri, 2 Feb 2024 18:28:52 +0800 Message-ID: <20240202102857.110210-19-peterx@redhat.com> In-Reply-To: <20240202102857.110210-1-peterx@redhat.com> References: <20240202102857.110210-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.292, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1706869925397100003 Content-Type: text/plain; charset="utf-8" From: Peter Xu The current multifd_queue_page() is not easy to read and follow. It is not good with a few reasons: - No helper at all to show what exactly does a condition mean; in short, readability is low. - Rely on pages->ramblock being cleared to detect an empty queue. It's slightly an overload of the ramblock pointer, per Fabiano [1], which I also agree. - Contains a self recursion, even if not necessary.. Rewrite this function. We add some comments to make it even clearer on what it does. [1] https://lore.kernel.org/r/87wmrpjzew.fsf@suse.de Signed-off-by: Peter Xu Reviewed-by: Fabiano Rosas --- migration/multifd.c | 56 ++++++++++++++++++++++++++++++--------------- 1 file changed, 37 insertions(+), 19 deletions(-) diff --git a/migration/multifd.c b/migration/multifd.c index 35d4e8ad1f..4ab8e6eff2 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -506,35 +506,53 @@ static bool multifd_send_pages(void) return true; } =20 +static inline bool multifd_queue_empty(MultiFDPages_t *pages) +{ + return pages->num =3D=3D 0; +} + +static inline bool multifd_queue_full(MultiFDPages_t *pages) +{ + return pages->num =3D=3D pages->allocated; +} + +static inline void multifd_enqueue(MultiFDPages_t *pages, ram_addr_t offse= t) +{ + pages->offset[pages->num++] =3D offset; +} + /* Returns true if enqueue successful, false otherwise */ bool multifd_queue_page(RAMBlock *block, ram_addr_t offset) { - MultiFDPages_t *pages =3D multifd_send_state->pages; - bool changed =3D false; + MultiFDPages_t *pages; + +retry: + pages =3D multifd_send_state->pages; =20 - if (!pages->block) { + /* If the queue is empty, we can already enqueue now */ + if (multifd_queue_empty(pages)) { pages->block =3D block; + multifd_enqueue(pages, offset); + return true; } =20 - if (pages->block =3D=3D block) { - pages->offset[pages->num] =3D offset; - pages->num++; - - if (pages->num < pages->allocated) { - return true; + /* + * Not empty, meanwhile we need a flush. It can because of either: + * + * (1) The page is not on the same ramblock of previous ones, or, + * (2) The queue is full. + * + * After flush, always retry. + */ + if (pages->block !=3D block || multifd_queue_full(pages)) { + if (!multifd_send_pages()) { + return false; } - } else { - changed =3D true; - } - - if (!multifd_send_pages()) { - return false; - } - - if (changed) { - return multifd_queue_page(block, offset); + goto retry; } =20 + /* Not empty, and we still have space, do it! */ + multifd_enqueue(pages, offset); return true; } =20 --=20 2.43.0