Re: [External] [PATCH v2 05/23] migration/multifd: Drop MultiFDSendParams.normal[] array

[Fabiano Rosas]

Hao Xiang <hao.xiang@bytedance.com> writes:

> On Fri, Feb 2, 2024 at 2:30 AM <peterx@redhat.com> wrote:
>>
>> From: Peter Xu <peterx@redhat.com>
>>
>> This array is redundant when p->pages exists.  Now we extended the life of
>> p->pages to the whole period where pending_job is set, it should be safe to
>> always use p->pages->offset[] rather than p->normal[].  Drop the array.
>>
>> Alongside, the normal_num is also redundant, which is the same to
>> p->pages->num.
>
> Can we not drop p->normal and p_normal_num? It is redundant now but I
> think it will be needed for multifd zero page checking. In multifd
> zero page, we find out all zero pages and we sort the normal pages and
> zero pages in two seperate arrays. p->offset is the original array of
> pages, p->normal will contain the array of normal pages and p->zero
> will contain the array of zero pages.

We're moving send_fill_packet into send_prepare(), so you should be able
to do whatever data transformation at send_prepare() and add any fields
you need into p->pages.

If we keep p->normal we will not be able to switch into an opaque
payload later on. There should be no mention of pages outside of
hooks. This is long-term work, but let's avoid blocking it if possible.

>>
>> This doesn't apply to recv side, because there's no extra buffering on recv
>> side, so p->normal[] array is still needed.
>>
>> Reviewed-by: Fabiano Rosas <farosas@suse.de>
>> Signed-off-by: Peter Xu <peterx@redhat.com>
>> ---
>>  migration/multifd.h      |  4 ----
>>  migration/multifd-zlib.c |  7 ++++---
>>  migration/multifd-zstd.c |  7 ++++---
>>  migration/multifd.c      | 33 +++++++++++++--------------------
>>  4 files changed, 21 insertions(+), 30 deletions(-)
>>
>> diff --git a/migration/multifd.h b/migration/multifd.h
>> index 7c040cb85a..3920bdbcf1 100644
>> --- a/migration/multifd.h
>> +++ b/migration/multifd.h
>> @@ -122,10 +122,6 @@ typedef struct {
>>      struct iovec *iov;
>>      /* number of iovs used */
>>      uint32_t iovs_num;
>> -    /* Pages that are not zero */
>> -    ram_addr_t *normal;
>> -    /* num of non zero pages */
>> -    uint32_t normal_num;
>>      /* used for compression methods */
>>      void *data;
>>  }  MultiFDSendParams;
>> diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
>> index 37ce48621e..100809abc1 100644
>> --- a/migration/multifd-zlib.c
>> +++ b/migration/multifd-zlib.c
>> @@ -116,17 +116,18 @@ static void zlib_send_cleanup(MultiFDSendParams *p, 
>> Error **errp)
>>   */
>>  static int zlib_send_prepare(MultiFDSendParams *p, Error **errp)
>>  {
>> +    MultiFDPages_t *pages = p->pages;
>>      struct zlib_data *z = p->data;
>>      z_stream *zs = &z->zs;
>>      uint32_t out_size = 0;
>>      int ret;
>>      uint32_t i;
>>
>> -    for (i = 0; i < p->normal_num; i++) {
>> +    for (i = 0; i < pages->num; i++) {
>>          uint32_t available = z->zbuff_len - out_size;
>>          int flush = Z_NO_FLUSH;
>>
>> -        if (i == p->normal_num - 1) {
>> +        if (i == pages->num - 1) {
>>              flush = Z_SYNC_FLUSH;
>>          }
>>
>> @@ -135,7 +136,7 @@ static int zlib_send_prepare(MultiFDSendParams *p, Error 
>> **errp)
>>           * with compression. zlib does not guarantee that this is safe,
>>           * therefore copy the page before calling deflate().
>>           */
>> -        memcpy(z->buf, p->pages->block->host + p->normal[i], p->page_size);
>> +        memcpy(z->buf, p->pages->block->host + pages->offset[i], 
>> p->page_size);
>>          zs->avail_in = p->page_size;
>>          zs->next_in = z->buf;
>>
>> diff --git a/migration/multifd-zstd.c b/migration/multifd-zstd.c
>> index b471daadcd..2023edd8cc 100644
>> --- a/migration/multifd-zstd.c
>> +++ b/migration/multifd-zstd.c
>> @@ -113,6 +113,7 @@ static void zstd_send_cleanup(MultiFDSendParams *p, 
>> Error **errp)
>>   */
>>  static int zstd_send_prepare(MultiFDSendParams *p, Error **errp)
>>  {
>> +    MultiFDPages_t *pages = p->pages;
>>      struct zstd_data *z = p->data;
>>      int ret;
>>      uint32_t i;
>> @@ -121,13 +122,13 @@ static int zstd_send_prepare(MultiFDSendParams *p, 
>> Error **errp)
>>      z->out.size = z->zbuff_len;
>>      z->out.pos = 0;
>>
>> -    for (i = 0; i < p->normal_num; i++) {
>> +    for (i = 0; i < pages->num; i++) {
>>          ZSTD_EndDirective flush = ZSTD_e_continue;
>>
>> -        if (i == p->normal_num - 1) {
>> +        if (i == pages->num - 1) {
>>              flush = ZSTD_e_flush;
>>          }
>> -        z->in.src = p->pages->block->host + p->normal[i];
>> +        z->in.src = p->pages->block->host + pages->offset[i];
>>          z->in.size = p->page_size;
>>          z->in.pos = 0;
>>
>> diff --git a/migration/multifd.c b/migration/multifd.c
>> index 5633ac245a..8bb1fd95cf 100644
>> --- a/migration/multifd.c
>> +++ b/migration/multifd.c
>> @@ -90,13 +90,13 @@ static int nocomp_send_prepare(MultiFDSendParams *p, 
>> Error **errp)
>>  {
>>      MultiFDPages_t *pages = p->pages;
>>
>> -    for (int i = 0; i < p->normal_num; i++) {
>> -        p->iov[p->iovs_num].iov_base = pages->block->host + p->normal[i];
>> +    for (int i = 0; i < pages->num; i++) {
>> +        p->iov[p->iovs_num].iov_base = pages->block->host + 
>> pages->offset[i];
>>          p->iov[p->iovs_num].iov_len = p->page_size;
>>          p->iovs_num++;
>>      }
>>
>> -    p->next_packet_size = p->normal_num * p->page_size;
>> +    p->next_packet_size = pages->num * p->page_size;
>>      p->flags |= MULTIFD_FLAG_NOCOMP;
>>      return 0;
>>  }
>> @@ -269,21 +269,22 @@ static void multifd_pages_clear(MultiFDPages_t *pages)
>>  static void multifd_send_fill_packet(MultiFDSendParams *p)
>>  {
>>      MultiFDPacket_t *packet = p->packet;
>> +    MultiFDPages_t *pages = p->pages;
>>      int i;
>>
>>      packet->flags = cpu_to_be32(p->flags);
>>      packet->pages_alloc = cpu_to_be32(p->pages->allocated);
>> -    packet->normal_pages = cpu_to_be32(p->normal_num);
>> +    packet->normal_pages = cpu_to_be32(pages->num);
>>      packet->next_packet_size = cpu_to_be32(p->next_packet_size);
>>      packet->packet_num = cpu_to_be64(p->packet_num);
>>
>> -    if (p->pages->block) {
>> -        strncpy(packet->ramblock, p->pages->block->idstr, 256);
>> +    if (pages->block) {
>> +        strncpy(packet->ramblock, pages->block->idstr, 256);
>>      }
>>
>> -    for (i = 0; i < p->normal_num; i++) {
>> +    for (i = 0; i < pages->num; i++) {
>>          /* there are architectures where ram_addr_t is 32 bit */
>> -        uint64_t temp = p->normal[i];
>> +        uint64_t temp = pages->offset[i];
>>
>>          packet->offset[i] = cpu_to_be64(temp);
>>      }
>> @@ -570,8 +571,6 @@ void multifd_save_cleanup(void)
>>          p->packet = NULL;
>>          g_free(p->iov);
>>          p->iov = NULL;
>> -        g_free(p->normal);
>> -        p->normal = NULL;
>>          multifd_send_state->ops->send_cleanup(p, &local_err);
>>          if (local_err) {
>>              migrate_set_error(migrate_get_current(), local_err);
>> @@ -688,8 +687,8 @@ static void *multifd_send_thread(void *opaque)
>>
>>          if (p->pending_job) {
>>              uint64_t packet_num = p->packet_num;
>> +            MultiFDPages_t *pages = p->pages;
>>              uint32_t flags;
>> -            p->normal_num = 0;
>>
>>              if (use_zero_copy_send) {
>>                  p->iovs_num = 0;
>> @@ -697,12 +696,7 @@ static void *multifd_send_thread(void *opaque)
>>                  p->iovs_num = 1;
>>              }
>>
>> -            for (int i = 0; i < p->pages->num; i++) {
>> -                p->normal[p->normal_num] = p->pages->offset[i];
>> -                p->normal_num++;
>> -            }
>> -
>> -            if (p->normal_num) {
>> +            if (pages->num) {
>>                  ret = multifd_send_state->ops->send_prepare(p, &local_err);
>>                  if (ret != 0) {
>>                      qemu_mutex_unlock(&p->mutex);
>> @@ -713,10 +707,10 @@ static void *multifd_send_thread(void *opaque)
>>              flags = p->flags;
>>              p->flags = 0;
>>              p->num_packets++;
>> -            p->total_normal_pages += p->normal_num;
>> +            p->total_normal_pages += pages->num;
>>              qemu_mutex_unlock(&p->mutex);
>>
>> -            trace_multifd_send(p->id, packet_num, p->normal_num, flags,
>> +            trace_multifd_send(p->id, packet_num, pages->num, flags,
>>                                 p->next_packet_size);
>>
>>              if (use_zero_copy_send) {
>> @@ -924,7 +918,6 @@ int multifd_save_setup(Error **errp)
>>          p->name = g_strdup_printf("multifdsend_%d", i);
>>          /* We need one extra place for the packet header */
>>          p->iov = g_new0(struct iovec, page_count + 1);
>> -        p->normal = g_new0(ram_addr_t, page_count);
>>          p->page_size = qemu_target_page_size();
>>          p->page_count = page_count;
>>
>> --
>> 2.43.0
>>