Re: [Qemu-devel] [PATCH v3 1/5] exec: Change RAMBlockIterFunc definition

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Yury Kotov (yury-kotov@yandex-team.ru) wrote:
> Currently, qemu_ram_foreach_* calls RAMBlockIterFunc with many
> block-specific arguments. But often iter func needs RAMBlock*.
> This refactoring is needed for fast access to RAMBlock flags from
> qemu_ram_foreach_block's callback. The only way to achieve this now
> is to call qemu_ram_block_from_host (which also enumerates blocks).
> 
> So, this patch reduces complexity of
> qemu_ram_foreach_block() -> cb() -> qemu_ram_block_from_host()
> from O(n^2) to O(n).
> 
> Fix RAMBlockIterFunc definition and add some functions to read
> RAMBlock* fields witch were passed.
> 
> Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(Please keep the review-by's if you've not changed stuff)

> ---
>  exec.c                    | 21 +++++++++++++++++----
>  include/exec/cpu-common.h |  6 ++++--
>  migration/postcopy-ram.c  | 36 +++++++++++++++++++++---------------
>  migration/rdma.c          |  7 +++++--
>  stubs/ram-block.c         | 15 +++++++++++++++
>  util/vfio-helpers.c       |  6 +++---
>  6 files changed, 65 insertions(+), 26 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 518064530b..bf71462929 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1972,6 +1972,21 @@ const char *qemu_ram_get_idstr(RAMBlock *rb)
>      return rb->idstr;
>  }
>  
> +void *qemu_ram_get_host_addr(RAMBlock *rb)
> +{
> +    return rb->host;
> +}
> +
> +ram_addr_t qemu_ram_get_offset(RAMBlock *rb)
> +{
> +    return rb->offset;
> +}
> +
> +ram_addr_t qemu_ram_get_used_length(RAMBlock *rb)
> +{
> +    return rb->used_length;
> +}
> +
>  bool qemu_ram_is_shared(RAMBlock *rb)
>  {
>      return rb->flags & RAM_SHARED;
> @@ -3961,8 +3976,7 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque)
>  
>      rcu_read_lock();
>      RAMBLOCK_FOREACH(block) {
> -        ret = func(block->idstr, block->host, block->offset,
> -                   block->used_length, opaque);
> +        ret = func(block, opaque);
>          if (ret) {
>              break;
>          }
> @@ -3981,8 +3995,7 @@ int qemu_ram_foreach_migratable_block(RAMBlockIterFunc func, void *opaque)
>          if (!qemu_ram_is_migratable(block)) {
>              continue;
>          }
> -        ret = func(block->idstr, block->host, block->offset,
> -                   block->used_length, opaque);
> +        ret = func(block, opaque);
>          if (ret) {
>              break;
>          }
> diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> index 63ec1f9b37..9cd1f94bc5 100644
> --- a/include/exec/cpu-common.h
> +++ b/include/exec/cpu-common.h
> @@ -72,6 +72,9 @@ ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host);
>  void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev);
>  void qemu_ram_unset_idstr(RAMBlock *block);
>  const char *qemu_ram_get_idstr(RAMBlock *rb);
> +void *qemu_ram_get_host_addr(RAMBlock *rb);
> +ram_addr_t qemu_ram_get_offset(RAMBlock *rb);
> +ram_addr_t qemu_ram_get_used_length(RAMBlock *rb);
>  bool qemu_ram_is_shared(RAMBlock *rb);
>  bool qemu_ram_is_uf_zeroable(RAMBlock *rb);
>  void qemu_ram_set_uf_zeroable(RAMBlock *rb);
> @@ -116,8 +119,7 @@ void cpu_flush_icache_range(hwaddr start, hwaddr len);
>  extern struct MemoryRegion io_mem_rom;
>  extern struct MemoryRegion io_mem_notdirty;
>  
> -typedef int (RAMBlockIterFunc)(const char *block_name, void *host_addr,
> -    ram_addr_t offset, ram_addr_t length, void *opaque);
> +typedef int (RAMBlockIterFunc)(RAMBlock *rb, void *opaque);
>  
>  int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
>  int qemu_ram_foreach_migratable_block(RAMBlockIterFunc func, void *opaque);
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index fa09dba534..b098816221 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -319,10 +319,10 @@ static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis)
>  
>  /* Callback from postcopy_ram_supported_by_host block iterator.
>   */
> -static int test_ramblock_postcopiable(const char *block_name, void *host_addr,
> -                             ram_addr_t offset, ram_addr_t length, void *opaque)
> +static int test_ramblock_postcopiable(RAMBlock *rb, void *opaque)
>  {
> -    RAMBlock *rb = qemu_ram_block_by_name(block_name);
> +    const char *block_name = qemu_ram_get_idstr(rb);
> +    ram_addr_t length = qemu_ram_get_used_length(rb);
>      size_t pagesize = qemu_ram_pagesize(rb);
>  
>      if (length % pagesize) {
> @@ -443,9 +443,12 @@ out:
>   * must be done right at the start prior to pre-copy.
>   * opaque should be the MIS.
>   */
> -static int init_range(const char *block_name, void *host_addr,
> -                      ram_addr_t offset, ram_addr_t length, void *opaque)
> +static int init_range(RAMBlock *rb, void *opaque)
>  {
> +    const char *block_name = qemu_ram_get_idstr(rb);
> +    void *host_addr = qemu_ram_get_host_addr(rb);
> +    ram_addr_t offset = qemu_ram_get_offset(rb);
> +    ram_addr_t length = qemu_ram_get_used_length(rb);
>      trace_postcopy_init_range(block_name, host_addr, offset, length);
>  
>      /*
> @@ -465,9 +468,12 @@ static int init_range(const char *block_name, void *host_addr,
>   * At the end of migration, undo the effects of init_range
>   * opaque should be the MIS.
>   */
> -static int cleanup_range(const char *block_name, void *host_addr,
> -                        ram_addr_t offset, ram_addr_t length, void *opaque)
> +static int cleanup_range(RAMBlock *rb, void *opaque)
>  {
> +    const char *block_name = qemu_ram_get_idstr(rb);
> +    void *host_addr = qemu_ram_get_host_addr(rb);
> +    ram_addr_t offset = qemu_ram_get_offset(rb);
> +    ram_addr_t length = qemu_ram_get_used_length(rb);
>      MigrationIncomingState *mis = opaque;
>      struct uffdio_range range_struct;
>      trace_postcopy_cleanup_range(block_name, host_addr, offset, length);
> @@ -586,9 +592,12 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
>  /*
>   * Disable huge pages on an area
>   */
> -static int nhp_range(const char *block_name, void *host_addr,
> -                    ram_addr_t offset, ram_addr_t length, void *opaque)
> +static int nhp_range(RAMBlock *rb, void *opaque)
>  {
> +    const char *block_name = qemu_ram_get_idstr(rb);
> +    void *host_addr = qemu_ram_get_host_addr(rb);
> +    ram_addr_t offset = qemu_ram_get_offset(rb);
> +    ram_addr_t length = qemu_ram_get_used_length(rb);
>      trace_postcopy_nhp_range(block_name, host_addr, offset, length);
>  
>      /*
> @@ -626,15 +635,13 @@ int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
>   *   opaque: MigrationIncomingState pointer
>   * Returns 0 on success
>   */
> -static int ram_block_enable_notify(const char *block_name, void *host_addr,
> -                                   ram_addr_t offset, ram_addr_t length,
> -                                   void *opaque)
> +static int ram_block_enable_notify(RAMBlock *rb, void *opaque)
>  {
>      MigrationIncomingState *mis = opaque;
>      struct uffdio_register reg_struct;
>  
> -    reg_struct.range.start = (uintptr_t)host_addr;
> -    reg_struct.range.len = length;
> +    reg_struct.range.start = (uintptr_t)qemu_ram_get_host_addr(rb);
> +    reg_struct.range.len = qemu_ram_get_used_length(rb);
>      reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
>  
>      /* Now tell our userfault_fd that it's responsible for this area */
> @@ -647,7 +654,6 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr,
>          return -1;
>      }
>      if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) {
> -        RAMBlock *rb = qemu_ram_block_by_name(block_name);
>          qemu_ram_set_uf_zeroable(rb);
>      }
>  
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 54a3c11540..7eb38ee764 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -624,9 +624,12 @@ static int rdma_add_block(RDMAContext *rdma, const char *block_name,
>   * in advanced before the migration starts. This tells us where the RAM blocks
>   * are so that we can register them individually.
>   */
> -static int qemu_rdma_init_one_block(const char *block_name, void *host_addr,
> -    ram_addr_t block_offset, ram_addr_t length, void *opaque)
> +static int qemu_rdma_init_one_block(RAMBlock *rb, void *opaque)
>  {
> +    const char *block_name = qemu_ram_get_idstr(rb);
> +    void *host_addr = qemu_ram_get_host_addr(rb);
> +    ram_addr_t block_offset = qemu_ram_get_offset(rb);
> +    ram_addr_t length = qemu_ram_get_used_length(rb);
>      return rdma_add_block(opaque, block_name, host_addr, block_offset, length);
>  }
>  
> diff --git a/stubs/ram-block.c b/stubs/ram-block.c
> index cfa5d8678f..73c0a3ee08 100644
> --- a/stubs/ram-block.c
> +++ b/stubs/ram-block.c
> @@ -2,6 +2,21 @@
>  #include "exec/ramlist.h"
>  #include "exec/cpu-common.h"
>  
> +void *qemu_ram_get_host_addr(RAMBlock *rb)
> +{
> +    return 0;
> +}
> +
> +ram_addr_t qemu_ram_get_offset(RAMBlock *rb)
> +{
> +    return 0;
> +}
> +
> +ram_addr_t qemu_ram_get_used_length(RAMBlock *rb)
> +{
> +    return 0;
> +}
> +
>  void ram_block_notifier_add(RAMBlockNotifier *n)
>  {
>  }
> diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
> index 342d4a2285..2367fe8f7f 100644
> --- a/util/vfio-helpers.c
> +++ b/util/vfio-helpers.c
> @@ -391,10 +391,10 @@ static void qemu_vfio_ram_block_removed(RAMBlockNotifier *n,
>      }
>  }
>  
> -static int qemu_vfio_init_ramblock(const char *block_name, void *host_addr,
> -                                   ram_addr_t offset, ram_addr_t length,
> -                                   void *opaque)
> +static int qemu_vfio_init_ramblock(RAMBlock *rb, void *opaque)
>  {
> +    void *host_addr = qemu_ram_get_host_addr(rb);
> +    ram_addr_t length = qemu_ram_get_used_length(rb);
>      int ret;
>      QEMUVFIOState *s = opaque;
>  
> -- 
> 2.20.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK