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Commit 51de4d90 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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[PATCH] taskstats: use nla_reserve() for reply assembling 



Currently taskstats_user_cmd()/taskstats_exit() do:

	1) allocate stats
	2) fill stats
	3) make a temporary copy on stack (236 bytes)
	4) copy that copy to skb
	5) free stats

With the help of nla_reserve() we can operate on skb->data directly,
thus avoiding all these steps except 2).

So, before this patch:

	// copy *stats to skb->data
	int mk_reply(skb, ..., struct taskstats *stats);

	fill_pid(stats);
	mk_reply(skb, ..., stats);

After:
	// return a pointer to skb->data
	struct taskstats *mk_reply(skb, ...);

	stat = mk_reply(skb, ...);
	fill_pid(stats);

Shrinks taskatsks.o by 162 bytes.

A stupid benchmark (send one million TASKSTATS_CMD_ATTR_PID) shows the

		real user sys
	before:
		4.02 0.06 3.96
		4.02 0.04 3.98
		4.02 0.04 3.97
	after:
		3.86 0.08 3.78
		3.88 0.10 3.77
		3.89 0.09 3.80

but this looks suspiciously good.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-by: default avatarShailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@sgi.com>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 68062b86

kernel/taskstats.c

+44 −42
Original line number Diff line number Diff line
@@ -185,6 +185,7 @@ static int fill_pid(pid_t pid, struct task_struct *tsk, 
	} else

		get_task_struct(tsk);



	memset(stats, 0, sizeof(*stats));

	/*

	 * Each accounting subsystem adds calls to its functions to

	 * fill in relevant parts of struct taskstsats as follows
@@ -227,6 +228,8 @@ static int fill_tgid(pid_t tgid, struct task_struct *first, 


	if (first->signal->stats)

		memcpy(stats, first->signal->stats, sizeof(*stats));

	else

		memset(stats, 0, sizeof(*stats));



	tsk = first;

	do {
@@ -343,9 +346,9 @@ static int parse(struct nlattr *na, cpumask_t *mask) 
	return ret;

}



static int mk_reply(struct sk_buff *skb, int type, u32 pid, struct taskstats *stats)

static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)

{

	struct nlattr *na;

	struct nlattr *na, *ret;

	int aggr;



	aggr = TASKSTATS_TYPE_AGGR_TGID;
@@ -353,20 +356,23 @@ static int mk_reply(struct sk_buff *skb, int type, u32 pid, struct taskstats *st 
		aggr = TASKSTATS_TYPE_AGGR_PID;



	na = nla_nest_start(skb, aggr);

	NLA_PUT_U32(skb, type, pid);

	NLA_PUT_TYPE(skb, struct taskstats, TASKSTATS_TYPE_STATS, *stats);

	if (nla_put(skb, type, sizeof(pid), &pid) < 0)

		goto err;

	ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));

	if (!ret)

		goto err;

	nla_nest_end(skb, na);



	return 0;

nla_put_failure:

	return -1;

	return nla_data(ret);

err:

	return NULL;

}



static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)

{

	int rc = 0;

	struct sk_buff *rep_skb;

	struct taskstats stats;

	struct taskstats *stats;

	void *reply;

	size_t size;

	cpumask_t mask;
@@ -389,36 +395,36 @@ static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info) 
	size = nla_total_size(sizeof(u32)) +

		nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);



	memset(&stats, 0, sizeof(stats));

	rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);

	if (rc < 0)

		return rc;



	rc = -EINVAL;

	if (info->attrs[TASKSTATS_CMD_ATTR_PID]) {

		u32 pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);

		rc = fill_pid(pid, NULL, &stats);

		if (rc < 0)

			goto err;

		stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, pid);

		if (!stats)

			goto nla_err;



		if (mk_reply(rep_skb, TASKSTATS_TYPE_PID, pid, &stats))

			goto nla_put_failure;

		rc = fill_pid(pid, NULL, stats);

		if (rc < 0)

			goto nla_err;

	} else if (info->attrs[TASKSTATS_CMD_ATTR_TGID]) {

		u32 tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);

		rc = fill_tgid(tgid, NULL, &stats);

		if (rc < 0)

			goto err;

		stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tgid);

		if (!stats)

			goto nla_err;



		if (mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tgid, &stats))

			goto nla_put_failure;

	} else {

		rc = -EINVAL;

		rc = fill_tgid(tgid, NULL, stats);

		if (rc < 0)

			goto nla_err;

	} else

		goto err;

	}



	return send_reply(rep_skb, info->snd_pid);



nla_put_failure:

	rc = genlmsg_cancel(rep_skb, reply);

nla_err:

	genlmsg_cancel(rep_skb, reply);

err:

	nlmsg_free(rep_skb);

	return rc;
@@ -453,7 +459,7 @@ void taskstats_exit(struct task_struct *tsk, int group_dead) 
{

	int rc;

	struct listener_list *listeners;

	struct taskstats *tidstats;

	struct taskstats *stats;

	struct sk_buff *rep_skb;

	void *reply;

	size_t size;
@@ -480,20 +486,17 @@ void taskstats_exit(struct task_struct *tsk, int group_dead) 
	if (list_empty(&listeners->list))

		return;



	tidstats = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);

	if (!tidstats)

		return;



	rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);

	if (rc < 0)

		goto free_stats;

		return;



	rc = fill_pid(tsk->pid, tsk, tidstats);

	if (rc < 0)

		goto err_skb;

	stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, tsk->pid);

	if (!stats)

		goto nla_err;



	if (mk_reply(rep_skb, TASKSTATS_TYPE_PID, tsk->pid, tidstats))

		goto nla_put_failure;

	rc = fill_pid(tsk->pid, tsk, stats);

	if (rc < 0)

		goto nla_err;



	/*

	 * Doesn't matter if tsk is the leader or the last group member leaving
@@ -501,20 +504,19 @@ void taskstats_exit(struct task_struct *tsk, int group_dead) 
	if (!is_thread_group || !group_dead)

		goto send;



	if (mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tsk->tgid, tsk->signal->stats))

		goto nla_put_failure;

	stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tsk->tgid);

	if (!stats)

		goto nla_err;



	memcpy(stats, tsk->signal->stats, sizeof(*stats));



send:

	send_cpu_listeners(rep_skb, listeners);

free_stats:

	kmem_cache_free(taskstats_cache, tidstats);

	return;



nla_put_failure:

nla_err:

	genlmsg_cancel(rep_skb, reply);

err_skb:

	nlmsg_free(rep_skb);

	goto free_stats;

}



static struct genl_ops taskstats_ops = {