Re: [Qemu-devel] [PATCH] Add interface to traverse the qmp command list by QmpCommand

[Eric Blake <eblake@redhat.com>]

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On 09/25/2013 07:56 PM, Mark Wu wrote:
> In the original code, qmp_get_command_list is used to construct
> a list of all commands' name. To get the information of all qga
> commands, it traverses the name list and search the command info
> with its name.  So it can cause O(n^2) in the number of commands.
> 
> This patch adds an interface to traverse the qmp command list by
> QmpCommand to replace qmp_get_command_list. It can decrease the
> complexity from O(n) to O(n^2)

from O(n^2) to O(n)

> 
> Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
> ---
>  include/qapi/qmp/dispatch.h |  3 +-
>  qapi/qmp-registry.c         | 28 ++-----------------
>  qga/commands.c              | 39 ++++++++++----------------
>  qga/main.c                  | 68 +++++++++++++++++----------------------------
>  4 files changed, 45 insertions(+), 93 deletions(-)
> 

>  
> -bool qmp_command_is_enabled(const char *name)

I think one of Michael's suggestions was that you may still want
qmp_command_is_enabled, but with a new signature:

bool qmp_command_is_enabled(const QmpCommand *cmd)
{
    return cmd->enabled;
}

> -struct GuestAgentInfo *qmp_guest_info(Error **err)
> +static void qmp_command_info(QmpCommand *cmd, void *opaque)
>   {
> -    GuestAgentInfo *info = g_malloc0(sizeof(GuestAgentInfo));
> +    GuestAgentInfo *info = (GuestAgentInfo *)opaque; 

This is C, not C++.  The cast is not necessary.

> -        cmd_info->enabled = qmp_command_is_enabled(cmd_info->name);
>  
> -        cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
> -        cmd_info_list->value = cmd_info;
> -        cmd_info_list->next = info->supported_commands;
> -        info->supported_commands = cmd_info_list;
> +    cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
> +    cmd_info->name = g_strdup(cmd->name);
> +    cmd_info->enabled = cmd->enabled;

I guess it all depends on whether we want QmpCommand to be an opaque
type outside of a single file.  But I don't have a strong argument for
making it opaque, and your approach works if we don't mind exposing the
details of QmpCommand across multiple files.  So I can live with your
patch as-is.


> +static void ga_enable_non_blacklisted(QmpCommand *cmd, void *opaque)
>  {

> +    GList *blacklist = (GList *)opaque;

Again, the cast is not necessary.

Overall, I like the patch.  Just a few tweaks suggested, but I can live
with you adding:

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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