linux-kernel - Re: seq_file: Use larger buffer to reduce time traversing lists

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Date:	Fri, 01 Jun 2012 08:54:56 -0700
From:	Joe Perches <joe@...ches.com>
To:	Steven Whitehouse <swhiteho@...hat.com>
Cc:	linux-kernel@...r.kernel.org, cluster-devel@...hat.com,
	Al Viro <viro@...iv.linux.org.uk>, nstraz@...hat.com
Subject: Re: seq_file: Use larger buffer to reduce time traversing lists

On Fri, 2012-06-01 at 11:39 +0100, Steven Whitehouse wrote:
> I've just been taking a look at the seq_read() code,
[]

nice improvement.  trivial style comment:

> diff --git a/fs/seq_file.c b/fs/seq_file.c
[]
> @@ -169,6 +171,16 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
>  	 */
>  	m->version = file->f_version;
>  
> +	if ((m->size < bsize) || !m->buf) {
> +		kfree(m->buf);
> +		m->size = 0;
> +		m->buf = kmalloc(m->size = bsize, GFP_KERNEL|__GFP_NOWARN);

You can remove the m->size = 0 line and
can you please add a space around the |?
It's a bit dense and too easy to read it
as a single word.
 
> +		if (!m->buf)
> +			m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
> +		if (!m->buf)
> +			goto Enomem;

Mixed case label?

> @@ -277,6 +289,11 @@ Done:
>  		m->read_pos += copied;
>  	}
>  	file->f_version = m->version;
> +	if (m->size > PAGE_SIZE) {
> +		kfree(m->buf);
> +		m->buf = NULL;
> +		m->size = 0;
> +	}
>  	mutex_unlock(&m->lock);
>  	return copied;
>  Enomem:

Oh, it wasn't you.  nevermind...

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