Re: [PATCH 10/19] readahead: state based method

[Eric Dumazet <dada1@cosmosbay.com>]

Wu Fengguang a écrit :

>  include/linux/fs.h |    8 +
> 
> --- linux-2.6.15-rc2-mm1.orig/include/linux/fs.h
> +++ linux-2.6.15-rc2-mm1/include/linux/fs.h
> @@ -604,13 +604,19 @@ struct file_ra_state {
>  	unsigned long start;		/* Current window */
>  	unsigned long size;
>  	unsigned long flags;		/* ra flags RA_FLAG_xxx*/
> -	unsigned long cache_hit;	/* cache hit count*/
> +	uint64_t      cache_hit;	/* cache hit count*/
>  	unsigned long prev_page;	/* Cache last read() position */
>  	unsigned long ahead_start;	/* Ahead window */
>  	unsigned long ahead_size;
>  	unsigned long ra_pages;		/* Maximum readahead window */
>  	unsigned long mmap_hit;		/* Cache hit stat for mmap accesses */
>  	unsigned long mmap_miss;	/* Cache miss stat for mmap accesses */
> +
> +	unsigned long age;
> +	pgoff_t la_index;
> +	pgoff_t ra_index;
> +	pgoff_t lookahead_index;
> +	pgoff_t readahead_index;
>  };

Hum... This sizeof(struct file) increase seems quite large...

Have you ever considered to change struct file so that file_ra_state is not 
embedded, but dynamically allocated (or other strategy) for regular files ?

I mean, sockets, pipes cannot readahead... And some machines use far more 
sockets than regular files.

I wrote such a patch in the past I could resend...

Eric