Re: [PATCH 04/11] PM: EM: Add the infrastructure for command processing.

[Changwoo Min <changwoo@igalia.com>]

On 6/2/25 04:59, Lukas Wunner wrote:
> On Thu, May 29, 2025 at 09:13:08AM +0900, Changwoo Min wrote:
>> +static int em_genl_cmd_doit(struct sk_buff *skb, struct genl_info *info)
>> +{
>> +	struct param p = { .attrs = info->attrs };
>> +	struct sk_buff *msg;
>> +	void *hdr;
>> +	int cmd = info->genlhdr->cmd;
>> +	int ret = -EMSGSIZE;
>> +
>> +	msg = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
>> +	if (!msg)
>> +		return -ENOMEM;
> 
> Just a heads-up, I know everyone recommends NLMSG_GOODSIZE but in reality
> it's not that great because netlink_trim() reallocates the skb and copies
> the entire linear buffer if it determines that the skb is half-empty.
> Performance suffers as a result.  So it's actually better to calculate
> the exact message length prior to allocation.
Thank you, Lukas, for sharing the experience. I will address it in the
next version.

Regards,
Changwoo Min