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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id n68-20020a1c2747000000b0038e6b4d5395sm70839wmn.16.2022.04.28.07.08.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Apr 2022 07:08:46 -0700 (PDT) Date: Thu, 28 Apr 2022 15:08:44 +0100 From: "Dr. David Alan Gilbert" To: Leonardo Bras Subject: Re: [PATCH v10 0/7] MSG_ZEROCOPY + multifd Message-ID: References: <20220426230654.637939-1-leobras@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220426230654.637939-1-leobras@redhat.com> User-Agent: Mutt/2.2.1 (2022-02-19) Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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: , Cc: Elena Ufimtseva , John G Johnson , Jagannathan Raman , qemu-block@nongnu.org, Juan Quintela , qemu-devel@nongnu.org, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Peter Xu , Markus Armbruster , Paolo Bonzini , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Fam Zheng , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Leonardo Bras (leobras@redhat.com) wrote: > This patch series intends to enable MSG_ZEROCOPY in QIOChannel, and make > use of it for multifd migration performance improvement, by reducing cpu > usage. > > Patch #1 creates new callbacks for QIOChannel, allowing the implementation > of zero copy writing. > > Patch #2 implements io_writev flags and io_flush() on QIOChannelSocket, > making use of MSG_ZEROCOPY on Linux. > > Patch #3 adds a "zero_copy_send" migration property, only available with > CONFIG_LINUX, and compiled-out in any other architectures. > This migration property has to be enabled before multifd migration starts. > > Patch #4 adds a helper function that allows to see if TLS is going to be used. > This helper will be later used in patch #5. > > Patch #5 changes multifd_send_sync_main() so it returns int instead of void. > The return value is used to understand if any error happened in the function, > allowing migration to possible fail earlier. > > Patch #6 implements an workaround: The behavior introduced in d48c3a0445 is > hard to deal with in zerocopy, so a workaround is introduced to send the > header in a different syscall, without MSG_ZEROCOPY. > > Patch #7 Makes use of QIOChannelSocket zero_copy implementation on > nocomp multifd migration. Queued. > Results: > In preliminary tests, the resource usage of __sys_sendmsg() reduced 15 times, > and the overall migration took 13-22% less time, based in synthetic cpu > workload. > > In further tests, it was noted that, on multifd migration with 8 channels: > - On idle hosts, migration time reduced in 10% to 21%. > - On hosts busy with heavy cpu stress (1 stress thread per cpu, but > not cpu-pinned) migration time reduced in ~25% by enabling zero-copy. > - On hosts with heavy cpu-pinned workloads (1 stress thread per cpu, > cpu-pinned), migration time reducted in ~66% by enabling zero-copy. Nice. > Above tests setup: > - Sending and Receiving hosts: > - CPU : Intel(R) Xeon(R) Platinum 8276L CPU @ 2.20GHz (448 CPUS) > - Network card: E810-C (100Gbps) > - >1TB RAM > - QEMU: Upstream master branch + This patchset > - Linux: Upstream v5.15 That configuration is particularly interesting because while it's a big machine with lots of cores, the individual cores are clocked relatively slowly; also having lots of cores probably means they're all fighting over memory bandwidth, so the less copies the better. Dave > - VM configuration: > - 28 VCPUs > - 512GB RAM > > > --- > Changes since v9: > - Patch #6 got simplified and improved (thanks Daniel) > - Patch #7 got better comments (thanks Peter Xu) > > Changes since v8: > - Inserted two new patches #5 & #6, previous patch #5 is now #7. > - Workaround an optimization introduced in d48c3a0445 > - Removed unnecessary assert in qio_channel_writev_full_all > > Changes since v7: > - Migration property renamed from zero-copy to zero-copy-send > - A few early tests added to help misconfigurations to fail earlier > - qio_channel_full*_flags() renamed back to qio_channel_full*() > - multifd_send_sync_main() reverted back to not receiving a flag, > so it always sync zero-copy when enabled. > - Improve code quality on a few points > > Changes since v6: > - Remove io_writev_zero_copy(), and makes use of io_writev() new flags > to achieve the same results. > - Rename io_flush_zero_copy() to io_flush() > - Previous patch #2 became too small, so it was squashed in previous > patch #3 (now patch #2) > > Changes since v5: > - flush_zero_copy now returns -1 on fail, 0 on success, and 1 when all > processed writes were not able to use zerocopy in kernel. > - qio_channel_socket_poll() removed, using qio_channel_wait() instead > - ENOBUFS is now processed inside qio_channel_socket_writev_flags() > - Most zerocopy parameter validation moved to migrate_params_check(), > leaving only feature test to socket_outgoing_migration() callback > - Naming went from *zerocopy to *zero_copy or *zero-copy, due to QAPI/QMP > preferences > - Improved docs > > Changes since v4: > - 3 patches got splitted in 6 > - Flush is used for syncing after each iteration, instead of only at the end > - If zerocopy is not available, fail in connect instead of failing on write > - 'multifd-zerocopy' property renamed to 'zerocopy' > - Fail migrations that don't support zerocopy, if it's enabled. > - Instead of checking for zerocopy at each write, save the flags in > MultiFDSendParams->write_flags and use them on write > - Reorganized flag usage in QIOChannelSocket > - A lot of typos fixed > - More doc on buffer restrictions > > Changes since v3: > - QIOChannel interface names changed from io_async_{writev,flush} to > io_{writev,flush}_zerocopy > - Instead of falling back in case zerocopy is not implemented, return > error and abort operation. > - Flush now waits as long as needed, or return error in case anything > goes wrong, aborting the operation. > - Zerocopy is now conditional in multifd, being set by parameter > multifd-zerocopy > - Moves zerocopy_flush to multifd_send_sync_main() from multifd_save_cleanup > so migration can abort if flush goes wrong. > - Several other small improvements > > Changes since v2: > - Patch #1: One more fallback > - Patch #2: Fall back to sync if fails to lock buffer memory in MSG_ZEROCOPY send. > > Changes since v1: > - Reimplemented the patchset using async_write + async_flush approach. > - Implemented a flush to be able to tell whenever all data was written. > > Leonardo Bras (7): > QIOChannel: Add flags on io_writev and introduce io_flush callback > QIOChannelSocket: Implement io_writev zero copy flag & io_flush for > CONFIG_LINUX > migration: Add zero-copy-send parameter for QMP/HMP for Linux > migration: Add migrate_use_tls() helper > multifd: multifd_send_sync_main now returns negative on error > multifd: Send header packet without flags if zero-copy-send is enabled > multifd: Implement zero copy write in multifd migration > (multifd-zero-copy) > > qapi/migration.json | 24 ++++++ > include/io/channel-socket.h | 2 + > include/io/channel.h | 38 +++++++++- > migration/migration.h | 6 ++ > migration/multifd.h | 4 +- > chardev/char-io.c | 2 +- > hw/remote/mpqemu-link.c | 2 +- > io/channel-buffer.c | 1 + > io/channel-command.c | 1 + > io/channel-file.c | 1 + > io/channel-socket.c | 110 +++++++++++++++++++++++++++- > io/channel-tls.c | 1 + > io/channel-websock.c | 1 + > io/channel.c | 49 ++++++++++--- > migration/channel.c | 3 +- > migration/migration.c | 52 ++++++++++++- > migration/multifd.c | 75 +++++++++++++++---- > migration/ram.c | 29 ++++++-- > migration/rdma.c | 1 + > migration/socket.c | 12 ++- > monitor/hmp-cmds.c | 6 ++ > scsi/pr-manager-helper.c | 2 +- > tests/unit/test-io-channel-socket.c | 1 + > 23 files changed, 379 insertions(+), 44 deletions(-) > > -- > 2.36.0 > > From c6fda6f8fb29ceeaf4d36f3787b85196e9bb281f Mon Sep 17 00:00:00 2001 > From: Leonardo Bras > Date: Mon, 25 Apr 2022 17:45:14 -0300 > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8 > Content-Transfer-Encoding: 8bit > To: "Marc-André Lureau" ,Paolo Bonzini ,Elena Ufimtseva ,Jagannathan Raman ,John G Johnson ,"Daniel P. Berrangé" ,Juan Quintela ,"Dr. David Alan Gilbert" ,Eric Blake ,Markus Armbruster ,Fam Zheng ,Peter Xu > Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, > > > Leonardo Bras (7): > QIOChannel: Add flags on io_writev and introduce io_flush callback > QIOChannelSocket: Implement io_writev zero copy flag & io_flush for > CONFIG_LINUX > migration: Add zero-copy-send parameter for QMP/HMP for Linux > migration: Add migrate_use_tls() helper > multifd: multifd_send_sync_main now returns negative on error > multifd: Send header packet without flags if zero-copy-send is enabled > multifd: Implement zero copy write in multifd migration > (multifd-zero-copy) > > qapi/migration.json | 24 ++++++ > include/io/channel-socket.h | 2 + > include/io/channel.h | 38 +++++++++- > migration/migration.h | 6 ++ > migration/multifd.h | 4 +- > chardev/char-io.c | 2 +- > hw/remote/mpqemu-link.c | 2 +- > io/channel-buffer.c | 1 + > io/channel-command.c | 1 + > io/channel-file.c | 1 + > io/channel-socket.c | 110 +++++++++++++++++++++++++++- > io/channel-tls.c | 1 + > io/channel-websock.c | 1 + > io/channel.c | 49 ++++++++++--- > migration/channel.c | 3 +- > migration/migration.c | 52 ++++++++++++- > migration/multifd.c | 72 +++++++++++++++--- > migration/ram.c | 29 ++++++-- > migration/rdma.c | 1 + > migration/socket.c | 12 ++- > monitor/hmp-cmds.c | 6 ++ > scsi/pr-manager-helper.c | 2 +- > tests/unit/test-io-channel-socket.c | 1 + > 23 files changed, 377 insertions(+), 43 deletions(-) > > -- > 2.36.0 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK