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Szmigiero" , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v6 19/19] migration/multifd: Add documentation for multifd methods In-Reply-To: References: <20240827174606.10352-1-farosas@suse.de> <20240827174606.10352-20-farosas@suse.de> <87mskxx0ck.fsf@suse.de> <87jzg1wza0.fsf@suse.de> Date: Tue, 27 Aug 2024 17:22:32 -0300 Message-ID: <87zfoxogvr.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 35739219EF X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_TLS_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MID_RHS_MATCH_FROM(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:dkim,suse.de:mid,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, 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 Peter Xu writes: > 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.. Yeah, this is a bit worrying. The reason this has not shown on valgrind or the asan that Peter ran recently is that uadk, qpl and soon qat are never enabled in a regular build. I have myself introduced compilation errors in those files that I only caught by accident at a later point (before sending to the ml). > > 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.. Should we maybe just free p->iov at the top level then?