* Juan Quintela ([email protected]) wrote:
> This implements the zero page dection and handling.
>
> Signed-off-by: Juan Quintela <[email protected]>
>
> ---
>
> Add comment for offset (dave)
> ---
> migration/multifd.h | 4 ++++
> migration/multifd.c | 36 ++++++++++++++++++++++++++++++++++--
> 2 files changed, 38 insertions(+), 2 deletions(-)
>
> diff --git a/migration/multifd.h b/migration/multifd.h
> index 4c6d29c954..d014747122 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -54,6 +54,10 @@ typedef struct {
> uint32_t unused32[1]; /* Reserved for future use */
> uint64_t unused64[3]; /* Reserved for future use */
> char ramblock[256];
> + /* This array contains the pointers to:
> + - normal pages (initial normal_pages entries)
> + - zero pages (following zero_pages entries)
> + */
> uint64_t offset[];
> } __attribute__((packed)) MultiFDPacket_t;
>
> diff --git a/migration/multifd.c b/migration/multifd.c
> index cfa9f75d13..ded13289e7 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -11,6 +11,7 @@
> */
>
> #include "qemu/osdep.h"
> +#include "qemu/cutils.h"
> #include "qemu/rcu.h"
> #include "exec/target_page.h"
> #include "sysemu/sysemu.h"
> @@ -277,6 +278,12 @@ static void multifd_send_fill_packet(MultiFDSendParams
> *p)
>
> packet->offset[i] = cpu_to_be64(temp);
> }
> + for (i = 0; i < p->zero_num; i++) {
> + /* there are architectures where ram_addr_t is 32 bit */
> + uint64_t temp = p->zero[i];
> +
> + packet->offset[p->normal_num + i] = cpu_to_be64(temp);
> + }
> }
>
> static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
> @@ -362,6 +369,18 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams
> *p, Error **errp)
> p->normal[i] = offset;
> }
>
> + for (i = 0; i < p->zero_num; i++) {
> + uint64_t offset = be64_to_cpu(packet->offset[p->normal_num + i]);
> +
> + if (offset > (block->used_length - page_size)) {
> + error_setg(errp, "multifd: offset too long %" PRIu64
> + " (max " RAM_ADDR_FMT ")",
> + offset, block->used_length);
> + return -1;
> + }
> + p->zero[i] = offset;
> + }
> +
> return 0;
> }
>
> @@ -627,6 +646,8 @@ static void *multifd_send_thread(void *opaque)
> {
> MultiFDSendParams *p = opaque;
> Error *local_err = NULL;
> + /* qemu older than 7.0 don't understand zero page on multifd channel */
> + bool use_zero_page = migrate_use_multifd_zero_page();
> int ret = 0;
>
> trace_multifd_send_thread_start(p->id);
> @@ -655,8 +676,15 @@ static void *multifd_send_thread(void *opaque)
> p->zero_num = 0;
>
> for (int i = 0; i < p->pages->num; i++) {
> - p->normal[p->normal_num] = p->pages->offset[i];
> - p->normal_num++;
> + if (use_zero_page &&
> + buffer_is_zero(p->pages->block->host +
> p->pages->offset[i],
> + qemu_target_page_size())) {
> + p->zero[p->zero_num] = p->pages->offset[i];
> + p->zero_num++;
> + } else {
> + p->normal[p->normal_num] = p->pages->offset[i];
> + p->normal_num++;
> + }
> }
>
> if (p->normal_num) {
> @@ -1115,6 +1143,10 @@ static void *multifd_recv_thread(void *opaque)
> }
> }
>
> + for (int i = 0; i < p->zero_num; i++) {
> + memset(p->host + p->zero[i], 0, qemu_target_page_size());
> + }
> +
On the existing code, it tries to avoid doing the memset if the target
page size matches; that avoids allocating the zero pages on the
destination host; should we try and do the same here?
Dave
> if (flags & MULTIFD_FLAG_SYNC) {
> qemu_sem_post(&multifd_recv_state->sem_sync);
> qemu_sem_wait(&p->sem_sync);
> --
> 2.34.1
>
--
Dr. David Alan Gilbert / [email protected] / Manchester, UK
