From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33557) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aO8q2-0006C1-09 for qemu-devel@nongnu.org; Tue, 26 Jan 2016 13:59:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aO8pz-0006Fp-50 for qemu-devel@nongnu.org; Tue, 26 Jan 2016 13:59:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39569) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aO8py-0006FG-QW for qemu-devel@nongnu.org; Tue, 26 Jan 2016 13:59:35 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id C7A37A0A48 for ; Tue, 26 Jan 2016 18:59:33 +0000 (UTC) Date: Tue, 26 Jan 2016 18:59:29 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20160126185928.GF2426@work-vm> References: <1452599056-27357-1-git-send-email-berrange@redhat.com> <1452599056-27357-9-git-send-email-berrange@redhat.com> <20160125193858.GI2464@work-vm> <20160125221554.GB7337@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160125221554.GB7337@redhat.com> Subject: Re: [Qemu-devel] [PATCH v1 08/22] migration: convert post-copy to use QIOChannelBuffer List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Amit Shah , qemu-devel@nongnu.org, Juan Quintela * Daniel P. Berrange (berrange@redhat.com) wrote: > On Mon, Jan 25, 2016 at 07:38:59PM +0000, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrange (berrange@redhat.com) wrote: > > > The post-copy code does some I/O to/from an intermediate > > > in-memory buffer rather than direct to the underlying > > > I/O channel. Switch this code to use QIOChannelBuffer > > > instead of QEMUSizedBuffer. > > > > > > Signed-off-by: Daniel P. Berrange > > > --- > > > docs/migration.txt | 4 ++-- > > > include/sysemu/sysemu.h | 2 +- > > > migration/migration.c | 15 +++++++-------- > > > migration/savevm.c | 41 +++++++++++++---------------------------- > > > 4 files changed, 23 insertions(+), 39 deletions(-) > > > > > > diff --git a/docs/migration.txt b/docs/migration.txt > > > index fda8d61..11703de 100644 > > > --- a/docs/migration.txt > > > +++ b/docs/migration.txt > > > @@ -403,8 +403,8 @@ listen thread: --- page -- page -- page -- page -- page -- > > > > > > On receipt of CMD_PACKAGED (1) > > > All the data associated with the package - the ( ... ) section in the > > > -diagram - is read into memory (into a QEMUSizedBuffer), and the main thread > > > -recurses into qemu_loadvm_state_main to process the contents of the package (2) > > > +diagram - is read into memory, and the main thread recurses into > > > +qemu_loadvm_state_main to process the contents of the package (2) > > > which contains commands (3,6) and devices (4...) > > > > > > On receipt of 'postcopy listen' - 3 -(i.e. the 1st command in the package) > > > diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h > > > index 3bb8897..0f59912 100644 > > > --- a/include/sysemu/sysemu.h > > > +++ b/include/sysemu/sysemu.h > > > @@ -120,7 +120,7 @@ void qemu_savevm_command_send(QEMUFile *f, enum qemu_vm_cmd command, > > > uint16_t len, uint8_t *data); > > > void qemu_savevm_send_ping(QEMUFile *f, uint32_t value); > > > void qemu_savevm_send_open_return_path(QEMUFile *f); > > > -int qemu_savevm_send_packaged(QEMUFile *f, const QEMUSizedBuffer *qsb); > > > +int qemu_savevm_send_packaged(QEMUFile *f, const char *buf, size_t len); > > > void qemu_savevm_send_postcopy_advise(QEMUFile *f); > > > void qemu_savevm_send_postcopy_listen(QEMUFile *f); > > > void qemu_savevm_send_postcopy_run(QEMUFile *f); > > > diff --git a/migration/migration.c b/migration/migration.c > > > index 715f069..e921b20 100644 > > > --- a/migration/migration.c > > > +++ b/migration/migration.c > > > @@ -33,6 +33,7 @@ > > > #include "qom/cpu.h" > > > #include "exec/memory.h" > > > #include "exec/address-spaces.h" > > > +#include "io/channel-buffer.h" > > > > > > #define MAX_THROTTLE (32 << 20) /* Migration transfer speed throttling */ > > > > > > @@ -1401,7 +1402,8 @@ static int await_return_path_close_on_source(MigrationState *ms) > > > static int postcopy_start(MigrationState *ms, bool *old_vm_running) > > > { > > > int ret; > > > - const QEMUSizedBuffer *qsb; > > > + QIOChannelBuffer *bioc; > > > + QEMUFile *fb; > > > int64_t time_at_stop = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); > > > migrate_set_state(ms, MIGRATION_STATUS_ACTIVE, > > > MIGRATION_STATUS_POSTCOPY_ACTIVE); > > > @@ -1456,11 +1458,9 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running) > > > * So we wrap the device state up in a package with a length at the start; > > > * to do this we use a qemu_buf to hold the whole of the device state. > > > */ > > > - QEMUFile *fb = qemu_bufopen("w", NULL); > > > - if (!fb) { > > > - error_report("Failed to create buffered file"); > > > - goto fail; > > > - } > > > + bioc = qio_channel_buffer_new(4096); > > > + fb = qemu_fopen_channel_input(QIO_CHANNEL(bioc)); > > > > Why is that _input ? > > A mistake - should be output given that the old code used "w". OK, that makes sense then. > > Also, what's your naming converntion; my 'qsb' was just an > > abbreviation of (Q)EMU(S)ized(B)uffer; what's a bioc? > > In the vast majority of cases where you just have a pointer > to the generic base class QIOChannel, then I'll use 'ioc' as > the standard variable name - ie 'io' and 'c' for channel. > > If I have a specialized subtype, I prefix a single letter > reflecting the name of the subtype. eg 's' for QIOChannelSocket > giving "sioc" and 'b' for QIOChannelBuffer giving "bioc" etc. OK, my preference there would have been iocb just because it's the same order as the thing it's abbreviating; but that's just a personal preference. > > > + object_unref(OBJECT(bioc)); > > > > > > /* > > > * Make sure the receiver can get incoming pages before we send the rest > > > @@ -1474,10 +1474,9 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running) > > > qemu_savevm_send_postcopy_run(fb); > > > > > > /* <><> end of stuff going into the package */ > > > - qsb = qemu_buf_get(fb); > > > > > > /* Now send that blob */ > > > - if (qemu_savevm_send_packaged(ms->file, qsb)) { > > > + if (qemu_savevm_send_packaged(ms->file, bioc->data, bioc->usage)) { > > > goto fail_closefb; > > > } > > > qemu_fclose(fb); > > > diff --git a/migration/savevm.c b/migration/savevm.c > > > index 0ad1b93..f2e1880 100644 > > > --- a/migration/savevm.c > > > +++ b/migration/savevm.c > > > @@ -50,6 +50,7 @@ > > > #include "qemu/iov.h" > > > #include "block/snapshot.h" > > > #include "block/qapi.h" > > > +#include "io/channel-buffer.h" > > > > > > > > > #ifndef ETH_P_RARP > > > @@ -760,10 +761,8 @@ void qemu_savevm_send_open_return_path(QEMUFile *f) > > > * 0 on success > > > * -ve on error > > > */ > > > -int qemu_savevm_send_packaged(QEMUFile *f, const QEMUSizedBuffer *qsb) > > > +int qemu_savevm_send_packaged(QEMUFile *f, const char *buf, size_t len) > > > { > > > - size_t cur_iov; > > > - size_t len = qsb_get_length(qsb); > > > uint32_t tmp; > > > > > > if (len > MAX_VM_CMD_PACKAGED_SIZE) { > > > @@ -777,18 +776,7 @@ int qemu_savevm_send_packaged(QEMUFile *f, const QEMUSizedBuffer *qsb) > > > trace_qemu_savevm_send_packaged(); > > > qemu_savevm_command_send(f, MIG_CMD_PACKAGED, 4, (uint8_t *)&tmp); > > > > > > - /* all the data follows (concatinating the iov's) */ > > > - for (cur_iov = 0; cur_iov < qsb->n_iov; cur_iov++) { > > > - /* The iov entries are partially filled */ > > > - size_t towrite = MIN(qsb->iov[cur_iov].iov_len, len); > > > - len -= towrite; > > > - > > > - if (!towrite) { > > > - break; > > > - } > > > - > > > - qemu_put_buffer(f, qsb->iov[cur_iov].iov_base, towrite); > > > - } > > > + qemu_put_buffer(f, (const uint8_t *)buf, len); > > > > > > return 0; > > > } > > > @@ -1548,9 +1536,8 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis) > > > static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis) > > > { > > > int ret; > > > - uint8_t *buffer; > > > uint32_t length; > > > - QEMUSizedBuffer *qsb; > > > + QIOChannelBuffer *bioc; > > > > > > length = qemu_get_be32(mis->from_src_file); > > > trace_loadvm_handle_cmd_packaged(length); > > > @@ -1559,28 +1546,26 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis) > > > error_report("Unreasonably large packaged state: %u", length); > > > return -1; > > > } > > > - buffer = g_malloc0(length); > > > - ret = qemu_get_buffer(mis->from_src_file, buffer, (int)length); > > > + > > > + bioc = qio_channel_buffer_new(length); > > > + ret = qemu_get_buffer(mis->from_src_file, > > > + (uint8_t *)bioc->data, > > > + (int)length); > > > > Actually, qemu_get_buffer takes a size_t now; so you can fix that at the same time. > > Great. > > > > > > if (ret != length) { > > > - g_free(buffer); > > > + object_unref(OBJECT(bioc)); > > > error_report("CMD_PACKAGED: Buffer receive fail ret=%d length=%d\n", > > > ret, length); > > > return (ret < 0) ? ret : -EAGAIN; > > > } > > > + bioc->usage += length; > > > > I'm a bit surprised you've not wrapped feeding the data > > into the qio_channel_buffer up a bit rather than having the callers > > prod at it's buffer/usage elements directly. > > I figured it was better to avoid extra memcpy's in the migration code, > so decided to directly pass the internal buffer to get_qemu_buffer(). Yes, avoiding copies is good; I was just thinking more of a function that incremented the usage or something like that. Dave > > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK