linux-kernel - Re: [PATCH 2/4] mm, page_alloc: warn

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Date:   Tue, 17 Jan 2017 15:01:35 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 2/4] mm, page_alloc: warn_alloc print nodemask

On Tue, 17 Jan 2017, Michal Hocko wrote:

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 57dc3c3b53c1..3e35eb04a28a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1912,8 +1912,8 @@ extern void si_meminfo_node(struct sysinfo *val, int nid);
>  extern unsigned long arch_reserved_kernel_pages(void);
>  #endif
>  
> -extern __printf(2, 3)
> -void warn_alloc(gfp_t gfp_mask, const char *fmt, ...);
> +extern __printf(3, 4)
> +void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...);
>  
>  extern void setup_per_cpu_pageset(void);
>  
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 8f4f306d804c..7f9c0ee18ae0 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3031,12 +3031,13 @@ static void warn_alloc_show_mem(gfp_t gfp_mask)
>  	show_mem(filter);
>  }
>  
> -void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
> +void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
>  {
>  	struct va_format vaf;
>  	va_list args;
>  	static DEFINE_RATELIMIT_STATE(nopage_rs, DEFAULT_RATELIMIT_INTERVAL,
>  				      DEFAULT_RATELIMIT_BURST);
> +	nodemask_t *nm = (nodemask) ? nodemask : &cpuset_current_mems_allowed;

Small nit: wouldn't it be helpful to know if ac->nodemask is actually NULL 
rather than setting it to cpuset_current_mems_allowed here?  We know the 
effective nodemask from cpuset_print_current_mems_allowed(), but we don't 
know if there's a bug in the page allocator which is failing to set 
ac->nodemask appropriately if we blindly set it here when cpusets are not 
enabled.

>  
>  	if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) ||
>  	    debug_guardpage_minorder() > 0)
> @@ -3050,7 +3051,8 @@ void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
>  	pr_cont("%pV", &vaf);
>  	va_end(args);
>  
> -	pr_cont(", mode:%#x(%pGg)\n", gfp_mask, &gfp_mask);
> +	pr_cont(", mode:%#x(%pGg), nodemask=%*pbl\n", gfp_mask, &gfp_mask, nodemask_pr_args(nm));
> +	cpuset_print_current_mems_allowed();
>  
>  	dump_stack();
>  	warn_alloc_show_mem(gfp_mask);
> @@ -3709,7 +3711,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  
>  	/* Make sure we know about allocations which stall for too long */
>  	if (time_after(jiffies, alloc_start + stall_timeout)) {
> -		warn_alloc(gfp_mask,
> +		warn_alloc(gfp_mask, ac->nodemask,
>  			"page allocation stalls for %ums, order:%u",
>  			jiffies_to_msecs(jiffies-alloc_start), order);
>  		stall_timeout += 10 * HZ;
> @@ -3743,7 +3745,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	}
>  
>  nopage:
> -	warn_alloc(gfp_mask,
> +	warn_alloc(gfp_mask, ac->nodemask,
>  			"page allocation failure: order:%u", order);
>  got_pg:
>  	return page;
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index b9999fc44aa6..0600bbbd1080 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1662,7 +1662,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
>  	return area->addr;
>  
>  fail:
> -	warn_alloc(gfp_mask,
> +	warn_alloc(gfp_mask, NULL,
>  			  "vmalloc: allocation failure, allocated %ld of %ld bytes",
>  			  (area->nr_pages*PAGE_SIZE), area->size);
>  	vfree(area->addr);
> @@ -1724,7 +1724,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
>  	return addr;
>  
>  fail:
> -	warn_alloc(gfp_mask,
> +	warn_alloc(gfp_mask, NULL,
>  			  "vmalloc: allocation failure: %lu bytes", real_size);
>  	return NULL;
>  }