Re: [PATCH 1/4] mm: cma: add currently allocated CMA buffers list to debugfs

[Joonsoo Kim <iamjoonsoo.kim@lge.com>]

On Fri, Feb 13, 2015 at 01:15:41AM +0300, Stefan Strogin wrote:
> /sys/kernel/debug/cma/cma-<N>/buffers contains a list of currently allocated
> CMA buffers for CMA region N when CONFIG_CMA_DEBUGFS is enabled.
> 
> Format is:
> 
> <base_phys_addr> - <end_phys_addr> (<size> kB), allocated by <PID> (<comm>)
>  <stack backtrace when the buffer had been allocated>
> 
> Signed-off-by: Stefan Strogin <s.strogin@partner.samsung.com>
> ---
>  include/linux/cma.h |   9 ++++
>  mm/cma.c            |   9 ++++
>  mm/cma.h            |  16 ++++++
>  mm/cma_debug.c      | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  4 files changed, 178 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> index 9384ba6..4c2c83c 100644
> --- a/include/linux/cma.h
> +++ b/include/linux/cma.h
> @@ -28,4 +28,13 @@ extern int cma_init_reserved_mem(phys_addr_t base,
>  					struct cma **res_cma);
>  extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
>  extern bool cma_release(struct cma *cma, struct page *pages, int count);
> +
> +#ifdef CONFIG_CMA_DEBUGFS
> +extern int cma_buffer_list_add(struct cma *cma, unsigned long pfn, int count);
> +extern void cma_buffer_list_del(struct cma *cma, unsigned long pfn, int count);
> +#else
> +#define cma_buffer_list_add(cma, pfn, count) { }
> +#define cma_buffer_list_del(cma, pfn, count) { }
> +#endif
> +

These could be in mm/cma.h rather than include/linux/cma.h.

>  #endif
> diff --git a/mm/cma.c b/mm/cma.c
> index 2609e20..ed269b0 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -34,6 +34,9 @@
>  #include <linux/cma.h>
>  #include <linux/highmem.h>
>  #include <linux/io.h>
> +#include <linux/list.h>
> +#include <linux/proc_fs.h>
> +#include <linux/time.h>
>  
>  #include "cma.h"
>  
> @@ -125,6 +128,8 @@ static int __init cma_activate_area(struct cma *cma)
>  #ifdef CONFIG_CMA_DEBUGFS
>  	INIT_HLIST_HEAD(&cma->mem_head);
>  	spin_lock_init(&cma->mem_head_lock);
> +	INIT_LIST_HEAD(&cma->buffers_list);
> +	mutex_init(&cma->list_lock);
>  #endif
>  
>  	return 0;
> @@ -408,6 +413,9 @@ struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
>  		start = bitmap_no + mask + 1;
>  	}
>  
> +	if (page)
> +		cma_buffer_list_add(cma, pfn, count);
> +
>  	pr_debug("%s(): returned %p\n", __func__, page);
>  	return page;
>  }
> @@ -440,6 +448,7 @@ bool cma_release(struct cma *cma, struct page *pages, int count)
>  
>  	free_contig_range(pfn, count);
>  	cma_clear_bitmap(cma, pfn, count);
> +	cma_buffer_list_del(cma, pfn, count);
>  
>  	return true;
>  }
> diff --git a/mm/cma.h b/mm/cma.h
> index 1132d73..98e5f79 100644
> --- a/mm/cma.h
> +++ b/mm/cma.h
> @@ -1,6 +1,8 @@
>  #ifndef __MM_CMA_H__
>  #define __MM_CMA_H__
>  
> +#include <linux/sched.h>
> +
>  struct cma {
>  	unsigned long   base_pfn;
>  	unsigned long   count;
> @@ -10,9 +12,23 @@ struct cma {
>  #ifdef CONFIG_CMA_DEBUGFS
>  	struct hlist_head mem_head;
>  	spinlock_t mem_head_lock;
> +	struct list_head buffers_list;
> +	struct mutex	list_lock;
>  #endif
>  };
>  
> +#ifdef CONFIG_CMA_DEBUGFS
> +struct cma_buffer {
> +	unsigned long pfn;
> +	unsigned long count;
> +	pid_t pid;
> +	char comm[TASK_COMM_LEN];
> +	unsigned long trace_entries[16];
> +	unsigned int nr_entries;
> +	struct list_head list;
> +};
> +#endif
> +
>  extern struct cma cma_areas[MAX_CMA_AREAS];
>  extern unsigned cma_area_count;
>  
> diff --git a/mm/cma_debug.c b/mm/cma_debug.c
> index 7e1d325..5acd937 100644
> --- a/mm/cma_debug.c
> +++ b/mm/cma_debug.c
> @@ -2,6 +2,7 @@
>   * CMA DebugFS Interface
>   *
>   * Copyright (c) 2015 Sasha Levin <sasha.levin@oracle.com>
> + * Copyright (c) 2015 Stefan Strogin <stefan.strogin@gmail.com>
>   */
>   
>  
> @@ -10,6 +11,8 @@
>  #include <linux/list.h>
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
> +#include <linux/mm_types.h>
> +#include <linux/stacktrace.h>
>  
>  #include "cma.h"
>  
> @@ -21,6 +24,99 @@ struct cma_mem {
>  
>  static struct dentry *cma_debugfs_root;
>  
> +/* Must be called under cma->list_lock */
> +static int __cma_buffer_list_add(struct cma *cma, unsigned long pfn, int count)
> +{
> +	struct cma_buffer *cmabuf;
> +	struct stack_trace trace;
> +
> +	cmabuf = kmalloc(sizeof(*cmabuf), GFP_KERNEL);
> +	if (!cmabuf) {
> +		pr_warn("%s(page %p, count %d): failed to allocate buffer list entry\n",
> +			__func__, pfn_to_page(pfn), count);
> +		return -ENOMEM;
> +	}
> +
> +	trace.nr_entries = 0;
> +	trace.max_entries = ARRAY_SIZE(cmabuf->trace_entries);
> +	trace.entries = &cmabuf->trace_entries[0];
> +	trace.skip = 2;
> +	save_stack_trace(&trace);
> +
> +	cmabuf->pfn = pfn;
> +	cmabuf->count = count;
> +	cmabuf->pid = task_pid_nr(current);
> +	cmabuf->nr_entries = trace.nr_entries;
> +	get_task_comm(cmabuf->comm, current);
> +
> +	list_add_tail(&cmabuf->list, &cma->buffers_list);
> +
> +	return 0;
> +}
> +
> +/**
> + * cma_buffer_list_add() - add a new entry to a list of allocated buffers
> + * @cma:     Contiguous memory region for which the allocation is performed.
> + * @pfn:     Base PFN of the allocated buffer.
> + * @count:   Number of allocated pages.
> + *
> + * This function adds a new entry to the list of allocated contiguous memory
> + * buffers in a CMA area. It uses the CMA area specificated by the device
> + * if available or the default global one otherwise.
> + */
> +int cma_buffer_list_add(struct cma *cma, unsigned long pfn, int count)
> +{
> +	int ret;
> +
> +	mutex_lock(&cma->list_lock);
> +	ret = __cma_buffer_list_add(cma, pfn, count);
> +	mutex_unlock(&cma->list_lock);
> +
> +	return ret;
> +}
> +
> +/**
> + * cma_buffer_list_del() - delete an entry from a list of allocated buffers
> + * @cma:   Contiguous memory region for which the allocation was performed.
> + * @pfn:   Base PFN of the released buffer.
> + * @count: Number of pages.
> + *
> + * This function deletes a list entry added by cma_buffer_list_add().
> + */
> +void cma_buffer_list_del(struct cma *cma, unsigned long pfn, int count)
> +{
> +	struct cma_buffer *cmabuf, *tmp;
> +	int found = 0;
> +	unsigned long buf_end_pfn, free_end_pfn = pfn + count;
> +
> +	mutex_lock(&cma->list_lock);
> +	list_for_each_entry_safe(cmabuf, tmp, &cma->buffers_list, list) {
> +
> +		buf_end_pfn = cmabuf->pfn + cmabuf->count;
> +		if (pfn <= cmabuf->pfn && free_end_pfn >= buf_end_pfn) {
> +			list_del(&cmabuf->list);
> +			kfree(cmabuf);
> +			found = 1;
> +		} else if (pfn <= cmabuf->pfn && free_end_pfn < buf_end_pfn) {
> +			cmabuf->count -= free_end_pfn - cmabuf->pfn;
> +			cmabuf->pfn = free_end_pfn;
> +			found = 1;
> +		} else if (pfn > cmabuf->pfn && pfn < buf_end_pfn) {
> +			if (free_end_pfn < buf_end_pfn)
> +				__cma_buffer_list_add(cma, free_end_pfn,
> +						buf_end_pfn - free_end_pfn);
> +			cmabuf->count = pfn - cmabuf->pfn;
> +			found = 1;
> +		}
> +	}
> +	mutex_unlock(&cma->list_lock);

This linear searching make cma_release() slow if we have many allocated
cma buffers. It wouldn't cause any problem?

Thanks.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>