linux-kernel - Re: [patch 5/7] dma-pool: add pool sizes to debugfs

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Date:   Wed, 15 Apr 2020 08:45:08 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     David Rientjes <rientjes@...gle.com>,
        Christoph Hellwig <hch@....de>
Cc:     Brijesh Singh <brijesh.singh@....com>,
        Jon Grimm <jon.grimm@....com>, Joerg Roedel <joro@...tes.org>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org
Subject: Re: [patch 5/7] dma-pool: add pool sizes to debugfs



On 4/14/20 7:04 PM, David Rientjes wrote:
> The atomic DMA pools can dynamically expand based on non-blocking
> allocations that need to use it.
> 
> Export the sizes of each of these pools, in bytes, through debugfs for
> measurement.
> 
> Suggested-by: Christoph Hellwig <hch@....de>
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>   kernel/dma/pool.c | 41 +++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 41 insertions(+)
> 
> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> index cf052314d9e4..3e22022c933b 100644
> --- a/kernel/dma/pool.c
> +++ b/kernel/dma/pool.c
> @@ -2,6 +2,7 @@
>   /*
>    * Copyright (C) 2020 Google LLC
>    */
> +#include <linux/debugfs.h>
>   #include <linux/dma-direct.h>
>   #include <linux/dma-noncoherent.h>
>   #include <linux/dma-contiguous.h>
> @@ -15,6 +16,11 @@
>   static struct gen_pool *atomic_pool_dma __ro_after_init;
>   static struct gen_pool *atomic_pool_dma32 __ro_after_init;
>   static struct gen_pool *atomic_pool_kernel __ro_after_init;
> +#ifdef CONFIG_DEBUG_FS

I don't think you need the #ifdef any more unless you just want to save 
space. All of the debugfs routines have versions for whether 
CONFIG_DEBUG_FS is defined or not.

> +static unsigned long pool_size_dma;
> +static unsigned long pool_size_dma32;
> +static unsigned long pool_size_kernel;
> +#endif
>   
>   #define DEFAULT_DMA_COHERENT_POOL_SIZE  SZ_256K
>   static size_t atomic_pool_size = DEFAULT_DMA_COHERENT_POOL_SIZE;
> @@ -29,6 +35,38 @@ static int __init early_coherent_pool(char *p)
>   }
>   early_param("coherent_pool", early_coherent_pool);
>   
> +#ifdef CONFIG_DEBUG_FS
> +static void __init dma_atomic_pool_debugfs_init(void)
> +{
> +	struct dentry *root;
> +
> +	root = debugfs_create_dir("dma_pools", NULL);
> +	if (IS_ERR_OR_NULL(root))
> +		return;

I believe GregKH went through and removed a lot of these error checks (see 
9e3926df8779 ("xgbe: no need to check return value of debugfs_create 
functions") for an example).

Thanks,
Tom

> +
> +	debugfs_create_ulong("pool_size_dma", 0400, root, &pool_size_dma);
> +	debugfs_create_ulong("pool_size_dma32", 0400, root, &pool_size_dma32);
> +	debugfs_create_ulong("pool_size_kernel", 0400, root, &pool_size_kernel);
> +}
> +
> +static void dma_atomic_pool_size_add(gfp_t gfp, size_t size)
> +{
> +	if (gfp & __GFP_DMA)
> +		pool_size_dma += size;
> +	else if (gfp & __GFP_DMA32)
> +		pool_size_dma32 += size;
> +	else
> +		pool_size_kernel += size;
> +}
> +#else
> +static inline void dma_atomic_pool_debugfs_init(void)
> +{
> +}
> +static inline void dma_atomic_pool_size_add(gfp_t gfp, size_t size)
> +{
> +}
> +#endif /* CONFIG_DEBUG_FS */
> +
>   static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
>   			      gfp_t gfp)
>   {
> @@ -76,6 +114,7 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
>   	if (ret)
>   		goto encrypt_mapping;
>   
> +	dma_atomic_pool_size_add(gfp, pool_size);
>   	return 0;
>   
>   encrypt_mapping:
> @@ -160,6 +199,8 @@ static int __init dma_atomic_pool_init(void)
>   		if (!atomic_pool_dma32)
>   			ret = -ENOMEM;
>   	}
> +
> +	dma_atomic_pool_debugfs_init();
>   	return ret;
>   }
>   postcore_initcall(dma_atomic_pool_init);
>