It would be astonishing to have this collect access patters for a few
weeks. Then have a process that finds sets of blocks that are often read
togeather, then finaly a defragger that takes block orders.
On Mon, 1 Jun 1998, Rogier Wolff wrote:
>
> Hi,
>
> Here is a patch that allows you to monitor disk accesses. This is
> useful to determine the actual disk access patterns of a system. For
> example, you could consider "defragging" the system such that your
> boot process becomes a linear read from disk.
>
> Instructions:
>
> Patch your 2.0.3x kernel using the patch below. Configure the new
> options, and After booting the new kernel, you will find a
> /proc/blkdev_log file that has all disk accesses. A "cat" of this file
> will show everything since last time you looked. "tail -f" works
> nicely too.
>
> The output is jiffies, r/w, device, blockno.
>
> If the ringbuffer overflows, this is also noted.
>
> If you want to monitor your boot process, you'd better empty the
> buffer closely after fsck-ing the root filesystem. Or define a much
> larger ringbuffer than the default 0x1000 entries (48 kbytes of kernel
> memory)
>
> A userlevel program could monitor this file and tell you what files
> are being accessed.
>
> The code quality is such that I wouldn't want it into the standard
> kernel yet. Some stuff is "in the wrong place".
>
> Anybody who tests this, please tell me. I'm interested.....
>
> Regards,
>
> Roger.
>
>
> diff -ur linux-2.0.33.clean/drivers/block/Config.in linux/drivers/block/Config.in
> --- linux-2.0.33.clean/drivers/block/Config.in Mon Aug 4 20:45:55 1997
> +++ linux/drivers/block/Config.in Mon Jun 1 16:01:28 1998
> @@ -52,6 +52,10 @@
> fi
> tristate 'XT harddisk support' CONFIG_BLK_DEV_XD
>
> +bool 'Log accesses to block devices' CONFIG_BLK_DEV_LOG
> +if [ "$CONFIG_BLK_DEV_LOG" = "y" ]; then
> + hex 'log size' CONFIG_LOGSIZE 0x1000
> +fi
>
> if [ "$CONFIG_BLK_DEV_HD_IDE" = "y" -o "$CONFIG_BLK_DEV_HD_ONLY" = "y" ]; then
> define_bool CONFIG_BLK_DEV_HD y
> diff -ur linux-2.0.33.clean/drivers/block/ll_rw_blk.c linux/drivers/block/ll_rw_blk.c
> --- linux-2.0.33.clean/drivers/block/ll_rw_blk.c Wed Feb 26 20:10:15 1997
> +++ linux/drivers/block/ll_rw_blk.c Mon Jun 1 23:18:14 1998
> @@ -280,6 +280,105 @@
> sti();
> }
>
> +
> +#ifdef CONFIG_BLK_DEV_LOG
> +
> +
> +#include <linux/malloc.h>
> +
> +struct ringbuf_s {
> + long timestamp;
> + unsigned int blkdev;
> + unsigned int sector;
> +};
> +
> +#define WRITEFLAG 0x80000000
> +
> +static struct ringbuf_s ringbuf[CONFIG_LOGSIZE];
> +static int overrun = 0;
> +static int head=0, tail=0;
> +
> +/* Return (part of) the block device access ringbuffer.
> + We simply return if we go near the pagelimit.
> + The next read will return the rest.
> + We return EOF when there is nothing in the buffer.
> + Use "tail -f" to monitor the file. */
> +
> +int get_blockdev_log (char *buffer)
> +{
> + char *p = buffer;
> +
> + while (tail != head) {
> + if (overrun) {
> + p += sprintf (p, "overrun: %d\n", overrun);
> + overrun = 0;
> + }
> + p += sprintf (p, "%ld %c %04x %x\n",
> + ringbuf[tail].timestamp,
> + ringbuf[tail].blkdev & WRITEFLAG? 'w':'r',
> + ringbuf[tail].blkdev &~WRITEFLAG,
> + ringbuf[tail].sector);
> + tail++;
> + if (tail > CONFIG_LOGSIZE) tail = 0;
> + if (p-buffer > 900) break;
> + }
> + return p-buffer;
> +}
> +
> +static int blk_dev_log_read(struct inode * inode, struct file * file,
> + char * buf, int count)
> +{
> + char *p;
> + int cnt;
> +
> + p = kmalloc (1000, GFP_USER);
> + if (!p) return -ENOMEM;
> +
> + cnt = get_blockdev_log (p);
> +
> + memcpy_tofs (buf, p, cnt);
> +
> + kfree (p);
> + return cnt;
> +}
> +static struct file_operations proc_log_operations = {
> + NULL, /* array_lseek */
> + blk_dev_log_read,
> + NULL, /* array_write */
> + NULL, /* array_readdir */
> + NULL, /* array_select */
> + NULL, /* array_ioctl */
> + NULL, /* mmap */
> + NULL, /* no special open code */
> + NULL, /* no special release code */
> + NULL /* can't fsync */
> +};
> +
> +struct inode_operations proc_blk_dev_log_inode_operations = {
> + &proc_log_operations, /* default base directory file-ops */
> + NULL, /* create */
> + NULL, /* lookup */
> + NULL, /* link */
> + NULL, /* unlink */
> + NULL, /* symlink */
> + NULL, /* mkdir */
> + NULL, /* rmdir */
> + NULL, /* mknod */
> + NULL, /* rename */
> + NULL, /* readlink */
> + NULL, /* follow_link */
> + NULL, /* readpage */
> + NULL, /* writepage */
> + NULL, /* bmap */
> + NULL, /* truncate */
> + NULL /* permission */
> +};
> +
> +#endif
> +
> +
> +
> +
> static void make_request(int major,int rw, struct buffer_head * bh)
> {
> unsigned int sector, count;
> @@ -288,6 +387,26 @@
>
> count = bh->b_size >> 9;
> sector = bh->b_rsector;
> +
> +#ifdef CONFIG_BLK_DEV_LOG
> + {
> + int nexthead;
> +
> + nexthead = head+1;
> + if (nexthead > CONFIG_LOGSIZE) nexthead = 0;
> +
> + if (nexthead == tail) {
> + tail++;
> + if (tail > CONFIG_LOGSIZE) tail = 0;
> + overrun++;
> + }
> + ringbuf[nexthead].timestamp = jiffies;
> + ringbuf[nexthead].blkdev = bh->b_dev;
> + if (rw) ringbuf[nexthead].blkdev |= WRITEFLAG;
> + ringbuf[nexthead].sector = sector;
> + head = nexthead;
> + }
> +#endif
>
> /* Uhhuh.. Nasty dead-lock possible here.. */
> if (buffer_locked(bh))
> diff -ur linux-2.0.33.clean/fs/proc/root.c linux/fs/proc/root.c
> --- linux-2.0.33.clean/fs/proc/root.c Tue Apr 30 12:09:45 1996
> +++ linux/fs/proc/root.c Mon Jun 1 23:10:48 1998
> @@ -25,6 +25,10 @@
>
> static unsigned char proc_alloc_map[PROC_NDYNAMIC / 8] = {0};
>
> +#ifdef CONFIG_BLK_DEV_LOG
> +extern struct inode_operations proc_blk_dev_log_inode_operations;
> +#endif
> +
> /*
> * These are the generic /proc directory operations. They
> * use the in-memory "struct proc_dir_entry" tree to parse
> @@ -250,6 +254,7 @@
> NULL /* permission */
> };
>
> +
> void proc_root_init(void)
> {
> static int done = 0;
> @@ -352,6 +357,15 @@
> PROC_CMDLINE, 7, "cmdline",
> S_IFREG | S_IRUGO, 1, 0, 0,
> });
> +
> +#ifdef CONFIG_BLK_DEV_LOG
> +
> + proc_register(&proc_root, &(struct proc_dir_entry) {
> + PROC_BLK_DEV_LOG, 12, "blockdev_log",
> + S_IFREG | S_IRUGO, 1, 0, 0,
> + 0, &proc_blk_dev_log_inode_operations,
> + });
> +#endif
> #ifdef CONFIG_RTC
> proc_register(&proc_root, &(struct proc_dir_entry) {
> PROC_RTC, 3, "rtc",
> diff -ur linux-2.0.33.clean/include/linux/proc_fs.h linux/include/linux/proc_fs.h
> --- linux-2.0.33.clean/include/linux/proc_fs.h Mon Jun 1 17:45:38 1998
> +++ linux/include/linux/proc_fs.h Mon Jun 1 18:14:29 1998
> @@ -43,6 +43,7 @@
> PROC_MTAB,
> PROC_MD,
> PROC_RTC,
> + PROC_BLK_DEV_LOG,
> PROC_LOCKS
> };
>
>
>
>
>
> --
> If it's there and you can see it, it's REAL |___R.E.Wolff@BitWizard.nl |
> If it's there and you can't see it, it's TRANSPARENT | Tel: +31-15-2137555 |
> If it's not there and you can see it, it's VIRTUAL |__FAX:_+31-15-2138217 |
> If it's not there and you can't see it, it's GONE! -- Roy Wilks, 1983 |_____|
>
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