linux-kernel - Re: [PATCH] vmpressure: implement strict mode

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Message-ID: <20130701085103.GA19798@amd.pavel.ucw.cz>
Date:	Mon, 1 Jul 2013 10:51:03 +0200
From:	Pavel Machek <pavel@....cz>
To:	Luiz Capitulino <lcapitulino@...hat.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org, mhocko@...e.cz,
	minchan@...nel.org, anton@...msg.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] vmpressure: implement strict mode

Hi!

> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> index ddf4f93..3c589cf 100644
> --- a/Documentation/cgroups/memory.txt
> +++ b/Documentation/cgroups/memory.txt
> @@ -807,12 +807,14 @@ register a notification, an application must:
>  
>  - create an eventfd using eventfd(2);
>  - open memory.pressure_level;
> -- write string like "<event_fd> <fd of memory.pressure_level> <level>"
> +- write string like "<event_fd> <fd of memory.pressure_level> <level> [strict]"
>    to cgroup.event_control.
>  

This is.. pretty strange interface. Would it be cleaner to do ioctl()?
New syscall?

> @@ -303,22 +307,33 @@ int vmpressure_register_event(struct cgroup *cg, struct cftype *cft,
>  {
>  	struct vmpressure *vmpr = cg_to_vmpressure(cg);
>  	struct vmpressure_event *ev;
> +	bool smode = false;
> +	const char *p;
>  	int level;
>  
>  	for (level = 0; level < VMPRESSURE_NUM_LEVELS; level++) {
> -		if (!strcmp(vmpressure_str_levels[level], args))
> +		p = vmpressure_str_levels[level];
> +		if (!strncmp(p, args, strlen(p)))
>  			break;
>  	}
>  
>  	if (level >= VMPRESSURE_NUM_LEVELS)
>  		return -EINVAL;
>  
> +	p = strchr(args, ' ');
> +	if (p) {
> +		if (strncmp(++p, "strict", 6))
> +			return -EINVAL;
> +		smode = true;
> +	}
> +

This looks like something for bash, not for kernel :-(.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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