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Re: [Qemu-devel] [PATCH v3 10/27] migration: convert post-copy to use QI
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v3 10/27] migration: convert post-copy to use QIOChannelBuffer |
Date: |
Thu, 10 Mar 2016 15:25:40 +0000 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
* Daniel P. Berrange (address@hidden) 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 <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> docs/migration.txt | 4 ++--
> include/sysemu/sysemu.h | 2 +-
> migration/migration.c | 15 +++++++--------
> migration/savevm.c | 47 ++++++++++++++++-------------------------------
> 4 files changed, 26 insertions(+), 42 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..ea488de 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 uint8_t *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 08720bc..c645443 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -34,6 +34,7 @@
> #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
> */
>
> @@ -1436,7 +1437,8 @@ 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->state, MIGRATION_STATUS_ACTIVE,
> MIGRATION_STATUS_POSTCOPY_ACTIVE);
> @@ -1495,11 +1497,9 @@ 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_output(QIO_CHANNEL(bioc));
> + object_unref(OBJECT(bioc));
>
> /*
> * Make sure the receiver can get incoming pages before we send the rest
> @@ -1513,10 +1513,9 @@ 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->to_dst_file, qsb)) {
> + if (qemu_savevm_send_packaged(ms->to_dst_file, bioc->data, bioc->usage))
> {
> goto fail_closefb;
> }
> qemu_fclose(fb);
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 94f2894..d2652fb 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 uint8_t *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, buf, len);
>
> return 0;
> }
> @@ -1556,39 +1544,36 @@ 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;
> + size_t length;
> + QIOChannelBuffer *bioc;
>
> length = qemu_get_be32(mis->from_src_file);
> trace_loadvm_handle_cmd_packaged(length);
>
> if (length > MAX_VM_CMD_PACKAGED_SIZE) {
> - error_report("Unreasonably large packaged state: %u", length);
> + error_report("Unreasonably large packaged state: %zu", 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,
> + bioc->data,
> + length);
> if (ret != length) {
> - g_free(buffer);
> - error_report("CMD_PACKAGED: Buffer receive fail ret=%d length=%d",
> + object_unref(OBJECT(bioc));
> + error_report("CMD_PACKAGED: Buffer receive fail ret=%d length=%zu",
> ret, length);
> return (ret < 0) ? ret : -EAGAIN;
> }
> + bioc->usage += length;
> trace_loadvm_handle_cmd_packaged_received(ret);
>
> - /* Setup a dummy QEMUFile that actually reads from the buffer */
> - qsb = qsb_create(buffer, length);
> - g_free(buffer); /* Because qsb_create copies */
> - if (!qsb) {
> - error_report("Unable to create qsb");
> - }
> - QEMUFile *packf = qemu_bufopen("r", qsb);
> + QEMUFile *packf = qemu_fopen_channel_input(QIO_CHANNEL(bioc));
>
> ret = qemu_loadvm_state_main(packf, mis);
> trace_loadvm_handle_cmd_packaged_main(ret);
> qemu_fclose(packf);
> - qsb_free(qsb);
> + object_unref(OBJECT(bioc));
>
> return ret;
> }
> --
> 2.5.0
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
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