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bh=sce7HrNOhUJdDp6p96pcte9MF5aX4MoQc31iYnuuyEw=; b=5XzDkxLFNRwDNXKE4x3sT3YlET0P/M/Zl847cCGkjm6SA1lwBQRymdxEQFrBjDFx5Dj/36 Fi9GqjSTkYp0c9Bw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id A66CC13991; Fri, 3 May 2024 20:49:34 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PkzKG95NNWaHCQAAD6G6ig (envelope-from ); Fri, 03 May 2024 20:49:34 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org, berrange@redhat.com, armbru@redhat.com, Claudio Fontana , Jim Fehlig , Eric Blake Subject: Re: [PATCH 4/9] migration: Add direct-io parameter In-Reply-To: References: <20240426142042.14573-1-farosas@suse.de> <20240426142042.14573-5-farosas@suse.de> Date: Fri, 03 May 2024 17:49:32 -0300 Message-ID: <871q6ioc2r.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Action: no action X-Rspamd-Queue-Id: 293F733CFA X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-6.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; DWL_DNSWL_MED(-2.00)[suse.de:dkim]; 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)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 Fri, Apr 26, 2024 at 11:20:37AM -0300, Fabiano Rosas wrote: >> Add the direct-io migration parameter that tells the migration code to >> use O_DIRECT when opening the migration stream file whenever possible. >> >> This is currently only used with the mapped-ram migration that has a >> clear window guaranteed to perform aligned writes. >> >> Acked-by: Markus Armbruster >> Signed-off-by: Fabiano Rosas >> --- >> include/qemu/osdep.h | 2 ++ >> migration/migration-hmp-cmds.c | 11 +++++++++++ >> migration/options.c | 30 ++++++++++++++++++++++++++++++ >> migration/options.h | 1 + >> qapi/migration.json | 18 +++++++++++++++--- >> util/osdep.c | 9 +++++++++ >> 6 files changed, 68 insertions(+), 3 deletions(-) >> >> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h >> index c7053cdc2b..645c14a65d 100644 >> --- a/include/qemu/osdep.h >> +++ b/include/qemu/osdep.h >> @@ -612,6 +612,8 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive); >> bool qemu_has_ofd_lock(void); >> #endif >> >> +bool qemu_has_direct_io(void); >> + >> #if defined(__HAIKU__) && defined(__i386__) >> #define FMT_pid "%ld" >> #elif defined(WIN64) >> diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c >> index 7e96ae6ffd..8496a2b34e 100644 >> --- a/migration/migration-hmp-cmds.c >> +++ b/migration/migration-hmp-cmds.c >> @@ -397,6 +397,13 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict) >> monitor_printf(mon, "%s: %s\n", >> MigrationParameter_str(MIGRATION_PARAMETER_MODE), >> qapi_enum_lookup(&MigMode_lookup, params->mode)); >> + >> + if (params->has_direct_io) { >> + monitor_printf(mon, "%s: %s\n", >> + MigrationParameter_str( >> + MIGRATION_PARAMETER_DIRECT_IO), >> + params->direct_io ? "on" : "off"); >> + } > > This will be the first parameter to optionally display here. I think it's > a sign of misuse of has_direct_io field.. > > IMHO has_direct_io should be best to be kept as "whether direct_io field is > valid" and that's all of it. It hopefully shouldn't contain more > information than that, or otherwise it'll be another small challenge we > need to overcome when we can remove all these has_* fields, and can also be > easily overlooked. I don't think I understand why we have those has_* fields. I thought my usage of 'params->has_direct_io = qemu_has_direct_io()' was the correct one, i.e. checking whether QEMU has any support for that parameter. Can you help me out here? > > IMHO what we should do is assert has_direct_io==true here too, meanwhile... > >> } >> >> qapi_free_MigrationParameters(params); >> @@ -690,6 +697,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict) >> p->has_mode = true; >> visit_type_MigMode(v, param, &p->mode, &err); >> break; >> + case MIGRATION_PARAMETER_DIRECT_IO: >> + p->has_direct_io = true; >> + visit_type_bool(v, param, &p->direct_io, &err); >> + break; >> default: >> assert(0); >> } >> diff --git a/migration/options.c b/migration/options.c >> index 239f5ecfb4..ae464aa4f2 100644 >> --- a/migration/options.c >> +++ b/migration/options.c >> @@ -826,6 +826,22 @@ int migrate_decompress_threads(void) >> return s->parameters.decompress_threads; >> } >> >> +bool migrate_direct_io(void) >> +{ >> + MigrationState *s = migrate_get_current(); >> + >> + /* For now O_DIRECT is only supported with mapped-ram */ >> + if (!s->capabilities[MIGRATION_CAPABILITY_MAPPED_RAM]) { >> + return false; >> + } >> + >> + if (s->parameters.has_direct_io) { >> + return s->parameters.direct_io; >> + } >> + >> + return false; >> +} >> + >> uint64_t migrate_downtime_limit(void) >> { >> MigrationState *s = migrate_get_current(); >> @@ -1061,6 +1077,11 @@ MigrationParameters *qmp_query_migrate_parameters(Error **errp) >> params->has_zero_page_detection = true; >> params->zero_page_detection = s->parameters.zero_page_detection; >> >> + if (s->parameters.has_direct_io) { >> + params->has_direct_io = true; >> + params->direct_io = s->parameters.direct_io; >> + } >> + >> return params; >> } >> >> @@ -1097,6 +1118,7 @@ void migrate_params_init(MigrationParameters *params) >> params->has_vcpu_dirty_limit = true; >> params->has_mode = true; >> params->has_zero_page_detection = true; >> + params->has_direct_io = qemu_has_direct_io(); >> } >> >> /* >> @@ -1416,6 +1438,10 @@ static void migrate_params_test_apply(MigrateSetParameters *params, >> if (params->has_zero_page_detection) { >> dest->zero_page_detection = params->zero_page_detection; >> } >> + >> + if (params->has_direct_io) { >> + dest->direct_io = params->direct_io; > > .. do proper check here to make sure the current QEMU is built with direct > IO support, then fail QMP migrate-set-parameters otherwise when someone > tries to enable it on a QEMU that doesn't support it. I'm already checking at migrate_params_init() with qemu_has_direct_io(). But ok, you want to move it here... Is this function the correct one instead of migrate_params_check()? I see these TODO comments mentioning QAPI_CLONE(), we can't clone the object if this one parameter needs special treatment. I might be getting all this wrong, bear with me. > > Always displaying direct_io parameter also helps when we simply want to > check qemu version and whether it supports this feature in general. > Makes sense. >> + } >> } >> >> static void migrate_params_apply(MigrateSetParameters *params, Error **errp) >> @@ -1570,6 +1596,10 @@ static void migrate_params_apply(MigrateSetParameters *params, Error **errp) >> if (params->has_zero_page_detection) { >> s->parameters.zero_page_detection = params->zero_page_detection; >> } >> + >> + if (params->has_direct_io) { >> + s->parameters.direct_io = params->direct_io; >> + } >> } >> >> void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp) >> diff --git a/migration/options.h b/migration/options.h >> index ab8199e207..aa5509cd2a 100644 >> --- a/migration/options.h >> +++ b/migration/options.h >> @@ -76,6 +76,7 @@ uint8_t migrate_cpu_throttle_increment(void); >> uint8_t migrate_cpu_throttle_initial(void); >> bool migrate_cpu_throttle_tailslow(void); >> int migrate_decompress_threads(void); >> +bool migrate_direct_io(void); >> uint64_t migrate_downtime_limit(void); >> uint8_t migrate_max_cpu_throttle(void); >> uint64_t migrate_max_bandwidth(void); >> diff --git a/qapi/migration.json b/qapi/migration.json >> index 8c65b90328..1a8a4b114c 100644 >> --- a/qapi/migration.json >> +++ b/qapi/migration.json >> @@ -914,6 +914,9 @@ >> # See description in @ZeroPageDetection. Default is 'multifd'. >> # (since 9.0) >> # >> +# @direct-io: Open migration files with O_DIRECT when possible. This >> +# requires that the @mapped-ram capability is enabled. (since 9.1) > > Here it seems to imply setting direct-io=true will fail if mapped-ram not > enabled, but in reality it's fine, it'll just be ignored. I think that's > the right thing to do to reduce correlation effects between params/caps > (otherwise, when unset mapped-ram cap, we'll need to double check again to > unset direct-io too; just cumbersome). > > I suggest we state the fact, that this field is ignored when mapped-ram > capability is not enabled, rather than "requires mapped-ram". Same to all > the rest two places in qapi doc. > Ok. >> +# >> # Features: >> # >> # @deprecated: Member @block-incremental is deprecated. Use >> @@ -948,7 +951,8 @@ >> { 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] }, >> 'vcpu-dirty-limit', >> 'mode', >> - 'zero-page-detection'] } >> + 'zero-page-detection', >> + 'direct-io'] } >> >> ## >> # @MigrateSetParameters: >> @@ -1122,6 +1126,9 @@ >> # See description in @ZeroPageDetection. Default is 'multifd'. >> # (since 9.0) >> # >> +# @direct-io: Open migration files with O_DIRECT when possible. This >> +# requires that the @mapped-ram capability is enabled. (since 9.1) >> +# >> # Features: >> # >> # @deprecated: Member @block-incremental is deprecated. Use >> @@ -1176,7 +1183,8 @@ >> 'features': [ 'unstable' ] }, >> '*vcpu-dirty-limit': 'uint64', >> '*mode': 'MigMode', >> - '*zero-page-detection': 'ZeroPageDetection'} } >> + '*zero-page-detection': 'ZeroPageDetection', >> + '*direct-io': 'bool' } } >> >> ## >> # @migrate-set-parameters: >> @@ -1354,6 +1362,9 @@ >> # See description in @ZeroPageDetection. Default is 'multifd'. >> # (since 9.0) >> # >> +# @direct-io: Open migration files with O_DIRECT when possible. This >> +# requires that the @mapped-ram capability is enabled. (since 9.1) >> +# >> # Features: >> # >> # @deprecated: Member @block-incremental is deprecated. Use >> @@ -1405,7 +1416,8 @@ >> 'features': [ 'unstable' ] }, >> '*vcpu-dirty-limit': 'uint64', >> '*mode': 'MigMode', >> - '*zero-page-detection': 'ZeroPageDetection'} } >> + '*zero-page-detection': 'ZeroPageDetection', >> + '*direct-io': 'bool' } } >> >> ## >> # @query-migrate-parameters: >> diff --git a/util/osdep.c b/util/osdep.c >> index e996c4744a..d0227a60ab 100644 >> --- a/util/osdep.c >> +++ b/util/osdep.c >> @@ -277,6 +277,15 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive) >> } >> #endif >> >> +bool qemu_has_direct_io(void) >> +{ >> +#ifdef O_DIRECT >> + return true; >> +#else >> + return false; >> +#endif >> +} >> + >> static int qemu_open_cloexec(const char *name, int flags, mode_t mode) >> { >> int ret; >> -- >> 2.35.3 >>