linux-kernel - Re: [PATCH -mm] relayfs: support larger relay buffer

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Date:	Tue, 15 Apr 2008 23:22:49 -0500
From:	Tom Zanussi <zanussi@...cast.net>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	David Wilder <dwilder@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	systemtap-ml <systemtap@...rces.redhat.com>,
	LKML <linux-kernel@...r.kernel.org>, tzanussi@...il.com
Subject: Re: [PATCH -mm] relayfs: support larger relay buffer


On Tue, 2008-04-15 at 11:27 -0400, Masami Hiramatsu wrote:
> Use vmalloc() and memset() instead of kcalloc() to allocate a page* array
> when the array size is bigger than one page. This enables relayfs to support
> bigger relay buffers than 64MB on 4k-page system, 512MB on 16k-page system.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
> ---
> This is useful for a 64-bit system which has a plenty of memory (tens of
> giga bytes) and a large kernel memory space.
> 
> I tested it on x86-64 and ia64.
> 

Hi,

It looks ok to me, but it might be a little cleaner and avoid some
duplication if you add the new code as a couple of functions instead.
Just a suggestion...

Tom

>  kernel/relay.c |   22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> Index: 2.6.25-rc8-mm2/kernel/relay.c
> ===================================================================
> --- 2.6.25-rc8-mm2.orig/kernel/relay.c
> +++ 2.6.25-rc8-mm2/kernel/relay.c
> @@ -104,12 +104,20 @@ static int relay_mmap_buf(struct rchan_b
>  static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
>  {
>  	void *mem;
> -	unsigned int i, j, n_pages;
> +	unsigned int i, j, n_pages, pa_size;
> 
>  	*size = PAGE_ALIGN(*size);
>  	n_pages = *size >> PAGE_SHIFT;
> +	pa_size = n_pages * sizeof(struct page *);
> 
> -	buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
> +	if (pa_size > PAGE_SIZE) {
> +		buf->page_array = vmalloc(pa_size);
> +		if (buf->page_array)
> +			memset(buf->page_array, 0, pa_size);
> +	} else {
> +		buf->page_array = kcalloc(n_pages, sizeof(struct page *),
> +					  GFP_KERNEL);
> +	}
>  	if (!buf->page_array)
>  		return NULL;
> 
> @@ -130,7 +138,10 @@ static void *relay_alloc_buf(struct rcha
>  depopulate:
>  	for (j = 0; j < i; j++)
>  		__free_page(buf->page_array[j]);
> -	kfree(buf->page_array);
> +	if (pa_size > PAGE_SIZE)
> +		vfree(buf->page_array);
> +	else
> +		kfree(buf->page_array);
>  	return NULL;
>  }
> 
> @@ -189,7 +200,10 @@ static void relay_destroy_buf(struct rch
>  		vunmap(buf->start);
>  		for (i = 0; i < buf->page_count; i++)
>  			__free_page(buf->page_array[i]);
> -		kfree(buf->page_array);
> +		if (buf->page_count * sizeof(struct page *) > PAGE_SIZE)
> +			vfree(buf->page_array);
> +		else
> +			kfree(buf->page_array);
>  	}
>  	chan->buf[buf->cpu] = NULL;
>  	kfree(buf->padding);

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