Re: [PATCH v6 4/6] connector/cn_proc: Performance improvements

[Liam R. Howlett]

* Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx> [230614 19:41]:
> This patch adds the capability to filter messages sent by the proc
> connector on the event type supplied in the message from the client
> to the connector. The client can register to listen for an event type
> given in struct proc_input.
> 
> This event based filteting will greatly enhance performance - handling
> 8K exits takes about 70ms, whereas 8K-forks + 8K-exits takes about 150ms
> & handling 8K-forks + 8K-exits + 8K-execs takes 200ms. There are currently
> 9 different types of events, and we need to listen to all of them. Also,
> measuring the time using pidfds for monitoring 8K process exits took
> much longer - 200ms, as compared to 70ms using only exit notifications of
> proc connector.
> 
> We also add a new event type - PROC_EVENT_NONZERO_EXIT, which is
> only sent by kernel to a listening application when any process exiting,
> has a non-zero exit status. This will help the clients like Oracle DB,
> where a monitoring process wants notfications for non-zero process exits
> so it can cleanup after them.
> 
> This kind of a new event could also be useful to other applications like
> Google's lmkd daemon, which needs a killed process's exit notification.
> 
> The patch takes care that existing clients using old mechanism of not
> sending the event type work without any changes.
> 
> cn_filter function checks to see if the event type being notified via
> proc connector matches the event type requested by client, before
> sending(matches) or dropping(does not match) a packet.
> 
> Signed-off-by: Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx>
> ---
>  drivers/connector/cn_proc.c  | 64 ++++++++++++++++++++++++++++++++----
>  include/uapi/linux/cn_proc.h | 19 +++++++++++
>  2 files changed, 77 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
> index 84f38d2bd4b9..825d5f506919 100644
> --- a/drivers/connector/cn_proc.c
> +++ b/drivers/connector/cn_proc.c
> @@ -50,21 +50,47 @@ static DEFINE_PER_CPU(struct local_event, local_event) = {
>  
>  static int cn_filter(struct sock *dsk, struct sk_buff *skb, void *data)
>  {
> +	uintptr_t val;
> +	__u32 what, exit_code, *ptr;
>  	enum proc_cn_mcast_op mc_op;

I guess reverse xmas tree would be requested here as well?

>  
> -	if (!dsk)
> +	if (!dsk || !data)
>  		return 0;
>  
> +	ptr = (__u32 *)data;
> +	what = *ptr++;
> +	exit_code = *ptr;
> +	val = ((struct proc_input *)(dsk->sk_user_data))->event_type;
>  	mc_op = ((struct proc_input *)(dsk->sk_user_data))->mcast_op;
>  
>  	if (mc_op == PROC_CN_MCAST_IGNORE)
>  		return 1;
>  
> -	return 0;
> +	if ((__u32)val == PROC_EVENT_ALL)
> +		return 0;
> +
> +	/*
> +	 * Drop packet if we have to report only non-zero exit status
> +	 * (PROC_EVENT_NONZERO_EXIT) and exit status is 0
> +	 */
> +	if (((__u32)val & PROC_EVENT_NONZERO_EXIT) &&
> +	    (what == PROC_EVENT_EXIT)) {
> +		if (exit_code)
> +			return 0;
> +		else

Nit: don't really need the else here.

> +			return 1;
> +	}
> +
> +	if ((__u32)val & what)
> +		return 0;
> +
> +	return 1;
>  }
>  
>  static inline void send_msg(struct cn_msg *msg)
>  {
> +	__u32 filter_data[2];
> +
>  	local_lock(&local_event.lock);
>  
>  	msg->seq = __this_cpu_inc_return(local_event.count) - 1;
> @@ -76,8 +102,16 @@ static inline void send_msg(struct cn_msg *msg)
>  	 *
>  	 * If cn_netlink_send() fails, the data is not sent.
>  	 */
> +	filter_data[0] = ((struct proc_event *)msg->data)->what;
> +	if (filter_data[0] == PROC_EVENT_EXIT) {
> +		filter_data[1] =
> +		((struct proc_event *)msg->data)->event_data.exit.exit_code;
> +	} else {
> +		filter_data[1] = 0;
> +	}
> +
>  	cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
> -			     cn_filter, NULL);
> +			     cn_filter, (void *)filter_data);
>  
>  	local_unlock(&local_event.lock);
>  }
> @@ -357,12 +391,15 @@ static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack)
>  
>  /**
>   * cn_proc_mcast_ctl
> - * @data: message sent from userspace via the connector
> + * @msg: message sent from userspace via the connector
> + * @nsp: NETLINK_CB of the client's socket buffer
>   */
>  static void cn_proc_mcast_ctl(struct cn_msg *msg,
>  			      struct netlink_skb_parms *nsp)
>  {
>  	enum proc_cn_mcast_op mc_op = 0, prev_mc_op = 0;
> +	struct proc_input *pinput = NULL;
> +	enum proc_cn_event ev_type = 0;
>  	int err = 0, initial = 0;
>  	struct sock *sk = NULL;
>  
> @@ -381,10 +418,21 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>  		goto out;
>  	}
>  
> -	if (msg->len == sizeof(mc_op))
> +	if (msg->len == sizeof(*pinput)) {
> +		pinput = (struct proc_input *)msg->data;
> +		mc_op = pinput->mcast_op;
> +		ev_type = pinput->event_type;
> +	} else if (msg->len == sizeof(mc_op)) {
>  		mc_op = *((enum proc_cn_mcast_op *)msg->data);
> -	else
> +		ev_type = PROC_EVENT_ALL;
> +	} else {
>  		return;
> +	}
> +
> +	ev_type = valid_event((enum proc_cn_event)ev_type);
> +
> +	if (ev_type == PROC_EVENT_NONE)
> +		ev_type = PROC_EVENT_ALL;
>  
>  	if (nsp->sk) {
>  		sk = nsp->sk;
> @@ -396,6 +444,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>  			prev_mc_op =
>  			((struct proc_input *)(sk->sk_user_data))->mcast_op;
>  		}
> +		((struct proc_input *)(sk->sk_user_data))->event_type =
> +			ev_type;
>  		((struct proc_input *)(sk->sk_user_data))->mcast_op = mc_op;
>  	}
>  
> @@ -407,6 +457,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>  	case PROC_CN_MCAST_IGNORE:
>  		if (!initial && (prev_mc_op != PROC_CN_MCAST_IGNORE))
>  			atomic_dec(&proc_event_num_listeners);
> +		((struct proc_input *)(sk->sk_user_data))->event_type =
> +			PROC_EVENT_NONE;
>  		break;
>  	default:
>  		err = EINVAL;
> diff --git a/include/uapi/linux/cn_proc.h b/include/uapi/linux/cn_proc.h
> index 6a06fb424313..f2afb7cc4926 100644
> --- a/include/uapi/linux/cn_proc.h
> +++ b/include/uapi/linux/cn_proc.h
> @@ -30,6 +30,15 @@ enum proc_cn_mcast_op {
>  	PROC_CN_MCAST_IGNORE = 2
>  };
>  
> +#define PROC_EVENT_ALL (PROC_EVENT_FORK | PROC_EVENT_EXEC | PROC_EVENT_UID |  \
> +			PROC_EVENT_GID | PROC_EVENT_SID | PROC_EVENT_PTRACE | \
> +			PROC_EVENT_COMM | PROC_EVENT_NONZERO_EXIT |           \
> +			PROC_EVENT_COREDUMP | PROC_EVENT_EXIT)
> +
> +/*
> + * If you add an entry in proc_cn_event, make sure you add it in
> + * PROC_EVENT_ALL above as well.
> + */
>  enum proc_cn_event {
>  	/* Use successive bits so the enums can be used to record
>  	 * sets of events as well
> @@ -45,15 +54,25 @@ enum proc_cn_event {
>  	/* "next" should be 0x00000400 */
>  	/* "last" is the last process event: exit,
>  	 * while "next to last" is coredumping event
> +	 * before that is report only if process dies
> +	 * with non-zero exit status
>  	 */
> +	PROC_EVENT_NONZERO_EXIT = 0x20000000,
>  	PROC_EVENT_COREDUMP = 0x40000000,
>  	PROC_EVENT_EXIT = 0x80000000
>  };
>  
>  struct proc_input {
>  	enum proc_cn_mcast_op mcast_op;
> +	enum proc_cn_event event_type;
>  };
>  
> +static inline enum proc_cn_event valid_event(enum proc_cn_event ev_type)
> +{
> +	ev_type &= PROC_EVENT_ALL;
> +	return ev_type;
> +}
> +
>  /*
>   * From the user's point of view, the process
>   * ID is the thread group ID and thread ID is the internal
> -- 
> 2.41.0
>