linux-kernel - Re: [PATCH] swiotlb: add debugfs to track swiotlb transient pool usage

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Date: Mon, 22 Jan 2024 16:18:45 +0800
From: "zhangpeng (AS)" <zhangpeng362@...wei.com>
To: <hch@....de>, <m.szyprowski@...sung.com>, <robin.murphy@....com>,
	<petr.tesarik1@...wei-partners.com>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
CC: <wangkefeng.wang@...wei.com>, <sunnanyong@...wei.com>
Subject: Re: [PATCH] swiotlb: add debugfs to track swiotlb transient pool
 usage

Kindly ping.

Could someone please review this patch? Comments are welcome.
Thanks.

On 2024/1/9 15:04, Peng Zhang wrote:

> From: ZhangPeng <zhangpeng362@...wei.com>
>
> Introduce a new debugfs interface io_tlb_transient_nslabs. The device
> driver can create a new swiotlb transient memory pool once default
> memory pool is full. To export the swiotlb transient memory pool usage
> via debugfs would help the user estimate the size of transient swiotlb
> memory pool or analyze device driver memory leak issue.
>
> Signed-off-by: ZhangPeng <zhangpeng362@...wei.com>
> ---
>   include/linux/swiotlb.h |  3 +++
>   kernel/dma/swiotlb.c    | 46 +++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 49 insertions(+)
>
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index ecde0312dd52..ea23097e351f 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -120,6 +120,8 @@ struct io_tlb_pool {
>    *		debugfs.
>    * @used_hiwater: The high water mark for total_used.  Used only for reporting
>    *		in debugfs.
> + * @transient_nslabs: The total number of slots in all transient pools that
> + *		are currently used across all areas.
>    */
>   struct io_tlb_mem {
>   	struct io_tlb_pool defpool;
> @@ -137,6 +139,7 @@ struct io_tlb_mem {
>   #ifdef CONFIG_DEBUG_FS
>   	atomic_long_t total_used;
>   	atomic_long_t used_hiwater;
> +	atomic_long_t transient_nslabs;
>   #endif
>   };
>   
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index b079a9a8e087..77974cea3e69 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -956,6 +956,28 @@ static void dec_used(struct io_tlb_mem *mem, unsigned int nslots)
>   }
>   #endif /* CONFIG_DEBUG_FS */
>   
> +#ifdef CONFIG_SWIOTLB_DYNAMIC
> +#ifdef CONFIG_DEBUG_FS
> +static void inc_transient_used(struct io_tlb_mem *mem, unsigned int nslots)
> +{
> +	atomic_long_add(nslots, &mem->transient_nslabs);
> +}
> +
> +static void dec_transient_used(struct io_tlb_mem *mem, unsigned int nslots)
> +{
> +	atomic_long_sub(nslots, &mem->transient_nslabs);
> +}
> +
> +#else /* !CONFIG_DEBUG_FS */
> +static void inc_transient_used(struct io_tlb_mem *mem, unsigned int nslots)
> +{
> +}
> +static void dec_transient_used(struct io_tlb_mem *mem, unsigned int nslots)
> +{
> +}
> +#endif /* CONFIG_DEBUG_FS */
> +#endif /* CONFIG_SWIOTLB_DYNAMIC */
> +
>   /**
>    * swiotlb_search_pool_area() - search one memory area in one pool
>    * @dev:	Device which maps the buffer.
> @@ -1170,6 +1192,7 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
>   	spin_lock_irqsave(&dev->dma_io_tlb_lock, flags);
>   	list_add_rcu(&pool->node, &dev->dma_io_tlb_pools);
>   	spin_unlock_irqrestore(&dev->dma_io_tlb_lock, flags);
> +	inc_transient_used(mem, pool->nslabs);
>   
>   found:
>   	WRITE_ONCE(dev->dma_uses_io_tlb, true);
> @@ -1415,6 +1438,7 @@ static bool swiotlb_del_transient(struct device *dev, phys_addr_t tlb_addr)
>   
>   	dec_used(dev->dma_io_tlb_mem, pool->nslabs);
>   	swiotlb_del_pool(dev, pool);
> +	dec_transient_used(dev->dma_io_tlb_mem, pool->nslabs);
>   	return true;
>   }
>   
> @@ -1557,6 +1581,23 @@ phys_addr_t default_swiotlb_limit(void)
>   }
>   
>   #ifdef CONFIG_DEBUG_FS
> +#ifdef CONFIG_SWIOTLB_DYNAMIC
> +static unsigned long mem_transient_used(struct io_tlb_mem *mem)
> +{
> +	return atomic_long_read(&mem->transient_nslabs);
> +}
> +
> +static int io_tlb_transient_used_get(void *data, u64 *val)
> +{
> +	struct io_tlb_mem *mem = data;
> +
> +	*val = mem_transient_used(mem);
> +	return 0;
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(fops_io_tlb_transient_used, io_tlb_transient_used_get,
> +			 NULL, "%llu\n");
> +#endif /* CONFIG_SWIOTLB_DYNAMIC */
>   
>   static int io_tlb_used_get(void *data, u64 *val)
>   {
> @@ -1605,6 +1646,11 @@ static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem,
>   			&fops_io_tlb_used);
>   	debugfs_create_file("io_tlb_used_hiwater", 0600, mem->debugfs, mem,
>   			&fops_io_tlb_hiwater);
> +#ifdef CONFIG_SWIOTLB_DYNAMIC
> +	atomic_long_set(&mem->transient_nslabs, 0);
> +	debugfs_create_file("io_tlb_transient_nslabs", 0400, mem->debugfs,
> +			    mem, &fops_io_tlb_transient_used);
> +#endif
>   }
>   
>   static int __init swiotlb_create_default_debugfs(void)

-- 
Best Regards,
Peng