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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a67f41cdbcsm575107285a.133.2024.08.27.12.44.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Aug 2024 12:44:39 -0700 (PDT) Date: Tue, 27 Aug 2024 15:44:37 -0400 From: Peter Xu To: Fabiano Rosas Cc: qemu-devel@nongnu.org, "Maciej S . Szmigiero" , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v6 19/19] migration/multifd: Add documentation for multifd methods Message-ID: References: <20240827174606.10352-1-farosas@suse.de> <20240827174606.10352-20-farosas@suse.de> <87mskxx0ck.fsf@suse.de> <87jzg1wza0.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87jzg1wza0.fsf@suse.de> 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Aug 27, 2024 at 04:17:59PM -0300, Fabiano Rosas wrote: > Peter Xu writes: > > > On Tue, Aug 27, 2024 at 03:54:51PM -0300, Fabiano Rosas wrote: > >> Peter Xu writes: > >> > >> > On Tue, Aug 27, 2024 at 02:46:06PM -0300, Fabiano Rosas wrote: > >> >> 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 > >> >> --- > >> >> Note that the doc is not symmetrical among send/recv because the recv > >> >> side is still wonky. It doesn't give the packet to the hooks, which > >> >> forces the p->normal, p->zero, etc. to be processed at the top level > >> >> of the threads, where no client-specific information should be. > >> >> --- > >> >> migration/multifd.h | 76 +++++++++++++++++++++++++++++++++++++++++---- > >> >> 1 file changed, 70 insertions(+), 6 deletions(-) > >> >> > >> >> diff --git a/migration/multifd.h b/migration/multifd.h > >> >> index 13e7a88c01..ebb17bdbcf 100644 > >> >> --- a/migration/multifd.h > >> >> +++ b/migration/multifd.h > >> >> @@ -229,17 +229,81 @@ typedef struct { > >> >> } MultiFDRecvParams; > >> >> > >> >> 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 > >> > > >> > Pure thoughts: wonder whether we can assert(p->iov) that after the hook > >> > returns in code to match this line. > >> > >> Not worth the extra instructions in my opinion. It would crash > >> immediately once the thread touches p->iov anyway. > > > > It might still be good IMHO to have that assert(), not only to abort > > earlier, but also as a code-styled comment. Your call when resend. > > > > PS: feel free to queue existing patches into your own tree without > > resending the whole series! > > > >> > >> > > >> >> + * 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. May be empty. > >> > > >> > Hmm, if we require p->iov allocation per-ops, then they must free it here? > >> > I wonder whether we leaked it in most compressors. > >> > >> Sorry, this one shouldn't have that text. > > > > I still want to double check with you: we leaked iov[] in most compressors > > here, or did I overlook something? > > They have their own send_cleanup function where p->iov is freed. Oh, so I guess I just accidentally stumbled upon multifd_uadk_send_cleanup() when looking.. I thought I looked a few more but now when I check most of them are indeed there but looks like uadk is missing that. I think it might still be a good idea to assert(iov==NULL) after the cleanup.. -- Peter Xu