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freebsd-dev/sys/kern/subr_disk.c
Kirk McKusick e03486d198 This checkin reimplements the io-request priority hack in a way 
that works in the new threaded kernel. It was commented out of
the disksort routine earlier this year for the reasons given in
kern/subr_disklabel.c (which is where this code used to reside
before it moved to kern/subr_disk.c):

----------------------------
revision 1.65
date: 2002/04/22 06:53:20;  author: phk;  state: Exp;  lines: +5 -0
Comment out Kirks io-request priority hack until we can do this in a
civilized way which doesn't cause grief.

The problem is that it is not generally safe to cast a "struct bio
*" to a "struct buf *".  Things like ccd, vinum, ata-raid and GEOM
constructs bio's which are not entrails of a struct buf.

Also, curthread may or may not have anything to do with the I/O request
at hand.

The correct solution can either be to tag struct bio's with a
priority derived from the requesting threads nice and have disksort
act on this field, this wouldn't address the "silly-seek syndrome"
where two equal processes bang the diskheads from one edge to the
other of the disk repeatedly.

Alternatively, and probably better: a sleep should be introduced
either at the time the I/O is requested or at the time it is completed
where we can be sure to sleep in the right thread.

The sleep also needs to be in constant timeunits, 1/hz can be practicaly
any sub-second size, at high HZ the current code practically doesn't
do anything.
----------------------------

As suggested in this comment, it is no longer located in the disk sort
routine, but rather now resides in spec_strategy where the disk operations
are being queued by the thread that is associated with the process that
is really requesting the I/O. At that point, the disk queues are not
visible, so the I/O for positively niced processes is always slowed
down whether or not there is other activity on the disk.

On the issue of scaling HZ, I believe that the current scheme is
better than using a fixed quantum of time. As machines and I/O
subsystems get faster, the resolution on the clock also rises.
So, ten years from now we will be slowing things down for shorter
periods of time, but the proportional effect on the system will
be about the same as it is today. So, I view this as a feature
rather than a drawback. Hence this patch sticks with using HZ.

Sponsored by:	DARPA & NAI Labs.
Reviewed by:	Poul-Henning Kamp <phk@critter.freebsd.dk>
2002-10-22 00:59:49 +00:00

602 lines
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/*
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
* ----------------------------------------------------------------------------
*
* $FreeBSD$
*
*/
#include "opt_geom.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/stdint.h>
#include <sys/bio.h>
#include <sys/conf.h>
#include <sys/disk.h>
#include <sys/diskslice.h>
#include <sys/disklabel.h>
#ifdef NO_GEOM
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <machine/md_var.h>
#include <sys/ctype.h>
static MALLOC_DEFINE(M_DISK, "disk", "disk data");
static d_strategy_t diskstrategy;
static d_open_t diskopen;
static d_close_t diskclose;
static d_ioctl_t diskioctl;
static d_psize_t diskpsize;
static LIST_HEAD(, disk) disklist = LIST_HEAD_INITIALIZER(&disklist);
void disk_dev_synth(dev_t dev);
void
disk_dev_synth(dev_t dev)
{
struct disk *dp;
int u, s, p;
dev_t pdev;
if (dksparebits(dev))
return;
LIST_FOREACH(dp, &disklist, d_list) {
if (major(dev) != dp->d_devsw->d_maj)
continue;
u = dkunit(dev);
p = RAW_PART;
s = WHOLE_DISK_SLICE;
pdev = makedev(dp->d_devsw->d_maj, dkmakeminor(u, s, p));
if (pdev->si_devsw == NULL)
return; /* Probably a unit we don't have */
s = dkslice(dev);
p = dkpart(dev);
if (s == WHOLE_DISK_SLICE && p == RAW_PART) {
/* XXX: actually should not happen */
dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%d",
dp->d_devsw->d_name, u);
dev_depends(pdev, dev);
return;
}
if (s == COMPATIBILITY_SLICE) {
dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%d%c",
dp->d_devsw->d_name, u, 'a' + p);
dev_depends(pdev, dev);
return;
}
if (p != RAW_PART) {
dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%ds%d%c",
dp->d_devsw->d_name, u, s - BASE_SLICE + 1,
'a' + p);
} else {
dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%ds%d",
dp->d_devsw->d_name, u, s - BASE_SLICE + 1);
make_dev_alias(dev, "%s%ds%dc",
dp->d_devsw->d_name, u, s - BASE_SLICE + 1);
}
dev_depends(pdev, dev);
return;
}
}
static void
disk_clone(void *arg, char *name, int namelen, dev_t *dev)
{
struct disk *dp;
char const *d;
char *e;
int j, u, s, p;
dev_t pdev;
if (*dev != NODEV)
return;
LIST_FOREACH(dp, &disklist, d_list) {
d = dp->d_devsw->d_name;
j = dev_stdclone(name, &e, d, &u);
if (j == 0)
continue;
if (u > DKMAXUNIT)
continue;
p = RAW_PART;
s = WHOLE_DISK_SLICE;
pdev = makedev(dp->d_devsw->d_maj, dkmakeminor(u, s, p));
if (pdev->si_disk == NULL)
continue;
if (*e != '\0') {
j = dev_stdclone(e, &e, "s", &s);
if (j == 0)
s = COMPATIBILITY_SLICE;
else if (j == 1 || j == 2)
s += BASE_SLICE - 1;
if (!*e)
; /* ad0s1 case */
else if (e[1] != '\0')
return; /* can never be a disk name */
else if (*e < 'a' || *e > 'h')
return; /* can never be a disk name */
else
p = *e - 'a';
}
if (s == WHOLE_DISK_SLICE && p == RAW_PART) {
return;
} else if (s >= BASE_SLICE && p != RAW_PART) {
*dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%ds%d%c",
pdev->si_devsw->d_name, u, s - BASE_SLICE + 1,
p + 'a');
} else if (s >= BASE_SLICE) {
*dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%ds%d",
pdev->si_devsw->d_name, u, s - BASE_SLICE + 1);
make_dev_alias(*dev, "%s%ds%dc",
pdev->si_devsw->d_name, u, s - BASE_SLICE + 1);
} else {
*dev = make_dev(pdev->si_devsw, dkmakeminor(u, s, p),
UID_ROOT, GID_OPERATOR, 0640, "%s%d%c",
pdev->si_devsw->d_name, u, p + 'a');
}
dev_depends(pdev, *dev);
return;
}
}
static void
inherit_raw(dev_t pdev, dev_t dev)
{
dev->si_disk = pdev->si_disk;
dev->si_drv1 = pdev->si_drv1;
dev->si_drv2 = pdev->si_drv2;
dev->si_iosize_max = pdev->si_iosize_max;
dev->si_bsize_phys = pdev->si_bsize_phys;
dev->si_bsize_best = pdev->si_bsize_best;
}
dev_t
disk_create(int unit, struct disk *dp, int flags, struct cdevsw *cdevsw, struct cdevsw *proto)
{
static int once;
dev_t dev;
if (!once) {
EVENTHANDLER_REGISTER(dev_clone, disk_clone, 0, 1000);
once++;
}
bzero(dp, sizeof(*dp));
dp->d_label = malloc(sizeof *dp->d_label, M_DEVBUF, M_WAITOK|M_ZERO);
if (proto->d_open != diskopen) {
*proto = *cdevsw;
proto->d_open = diskopen;
proto->d_close = diskclose;
proto->d_ioctl = diskioctl;
proto->d_strategy = diskstrategy;
proto->d_psize = diskpsize;
}
if (bootverbose)
printf("Creating DISK %s%d\n", cdevsw->d_name, unit);
dev = make_dev(proto, dkmakeminor(unit, WHOLE_DISK_SLICE, RAW_PART),
UID_ROOT, GID_OPERATOR, 0640, "%s%d", cdevsw->d_name, unit);
dev->si_disk = dp;
dp->d_dev = dev;
dp->d_dsflags = flags;
dp->d_devsw = cdevsw;
LIST_INSERT_HEAD(&disklist, dp, d_list);
return (dev);
}
static int
diskdumpconf(u_int onoff, dev_t dev, struct disk *dp)
{
struct dumperinfo di;
struct disklabel *dl;
if (!onoff)
return(set_dumper(NULL));
dl = dsgetlabel(dev, dp->d_slice);
if (!dl)
return (ENXIO);
bzero(&di, sizeof di);
di.dumper = (dumper_t *)dp->d_devsw->d_dump;
di.priv = dp->d_dev;
di.blocksize = dl->d_secsize;
di.mediaoffset = (off_t)(dl->d_partitions[dkpart(dev)].p_offset +
dp->d_slice->dss_slices[dkslice(dev)].ds_offset) * DEV_BSIZE;
di.mediasize =
(off_t)(dl->d_partitions[dkpart(dev)].p_size) * DEV_BSIZE;
if (di.mediasize == 0)
return (EINVAL);
return(set_dumper(&di));
}
void
disk_invalidate (struct disk *disk)
{
if (disk->d_slice)
dsgone(&disk->d_slice);
}
void
disk_destroy(dev_t dev)
{
LIST_REMOVE(dev->si_disk, d_list);
free(dev->si_disk->d_label, M_DEVBUF);
bzero(dev->si_disk, sizeof(*dev->si_disk));
dev->si_disk = NULL;
destroy_dev(dev);
return;
}
struct disk *
disk_enumerate(struct disk *disk)
{
if (!disk)
return (LIST_FIRST(&disklist));
else
return (LIST_NEXT(disk, d_list));
}
static int
sysctl_disks(SYSCTL_HANDLER_ARGS)
{
struct disk *disk;
int error, first;
disk = NULL;
first = 1;
while ((disk = disk_enumerate(disk))) {
if (!first) {
error = SYSCTL_OUT(req, " ", 1);
if (error)
return error;
} else {
first = 0;
}
error = SYSCTL_OUT(req, disk->d_dev->si_name, strlen(disk->d_dev->si_name));
if (error)
return error;
}
error = SYSCTL_OUT(req, "", 1);
return error;
}
SYSCTL_PROC(_kern, OID_AUTO, disks, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
sysctl_disks, "A", "names of available disks");
/*
* The cdevsw functions
*/
static int
diskopen(dev_t dev, int oflags, int devtype, struct thread *td)
{
dev_t pdev;
struct disk *dp;
int error;
error = 0;
pdev = dkmodpart(dkmodslice(dev, WHOLE_DISK_SLICE), RAW_PART);
dp = pdev->si_disk;
if (!dp)
return (ENXIO);
while (dp->d_flags & DISKFLAG_LOCK) {
dp->d_flags |= DISKFLAG_WANTED;
error = tsleep(dp, PRIBIO | PCATCH, "diskopen", hz);
if (error)
return (error);
}
dp->d_flags |= DISKFLAG_LOCK;
if (!dsisopen(dp->d_slice)) {
if (!pdev->si_iosize_max)
pdev->si_iosize_max = dev->si_iosize_max;
error = dp->d_devsw->d_open(pdev, oflags, devtype, td);
dp->d_label->d_secsize = dp->d_sectorsize;
dp->d_label->d_secperunit = dp->d_mediasize / dp->d_sectorsize;
dp->d_label->d_nsectors = dp->d_fwsectors;
dp->d_label->d_ntracks = dp->d_fwheads;
}
/* Inherit properties from the whole/raw dev_t */
inherit_raw(pdev, dev);
if (error)
goto out;
error = dsopen(dev, devtype, dp->d_dsflags, &dp->d_slice, dp->d_label);
if (!dsisopen(dp->d_slice))
dp->d_devsw->d_close(pdev, oflags, devtype, td);
out:
dp->d_flags &= ~DISKFLAG_LOCK;
if (dp->d_flags & DISKFLAG_WANTED) {
dp->d_flags &= ~DISKFLAG_WANTED;
wakeup(dp);
}
return(error);
}
static int
diskclose(dev_t dev, int fflag, int devtype, struct thread *td)
{
struct disk *dp;
int error;
dev_t pdev;
error = 0;
pdev = dkmodpart(dkmodslice(dev, WHOLE_DISK_SLICE), RAW_PART);
dp = pdev->si_disk;
if (!dp)
return (ENXIO);
dsclose(dev, devtype, dp->d_slice);
if (!dsisopen(dp->d_slice))
error = dp->d_devsw->d_close(dp->d_dev, fflag, devtype, td);
return (error);
}
static void
diskstrategy(struct bio *bp)
{
dev_t pdev;
struct disk *dp;
pdev = dkmodpart(dkmodslice(bp->bio_dev, WHOLE_DISK_SLICE), RAW_PART);
dp = pdev->si_disk;
bp->bio_resid = bp->bio_bcount;
if (dp != bp->bio_dev->si_disk)
inherit_raw(pdev, bp->bio_dev);
if (!dp) {
biofinish(bp, NULL, ENXIO);
return;
}
if (dscheck(bp, dp->d_slice) <= 0) {
biodone(bp);
return;
}
if (bp->bio_bcount == 0) {
biodone(bp);
return;
}
KASSERT(dp->d_devsw != NULL, ("NULL devsw"));
KASSERT(dp->d_devsw->d_strategy != NULL, ("NULL d_strategy"));
dp->d_devsw->d_strategy(bp);
return;
}
static int
diskioctl(dev_t dev, u_long cmd, caddr_t data, int fflag, struct thread *td)
{
struct disk *dp;
int error;
u_int u;
dev_t pdev;
pdev = dkmodpart(dkmodslice(dev, WHOLE_DISK_SLICE), RAW_PART);
dp = pdev->si_disk;
if (!dp)
return (ENXIO);
if (cmd == DIOCSKERNELDUMP) {
u = *(u_int *)data;
return (diskdumpconf(u, dev, dp));
}
if (cmd == DIOCGFRONTSTUFF) {
*(off_t *)data = 8192; /* XXX: crude but enough) */
return (0);
}
error = dsioctl(dev, cmd, data, fflag, &dp->d_slice);
if (error == ENOIOCTL)
error = dp->d_devsw->d_ioctl(dev, cmd, data, fflag, td);
return (error);
}
static int
diskpsize(dev_t dev)
{
struct disk *dp;
dev_t pdev;
pdev = dkmodpart(dkmodslice(dev, WHOLE_DISK_SLICE), RAW_PART);
dp = pdev->si_disk;
if (!dp)
return (-1);
if (dp != dev->si_disk) {
dev->si_drv1 = pdev->si_drv1;
dev->si_drv2 = pdev->si_drv2;
/* XXX: don't set bp->b_dev->si_disk (?) */
}
return (dssize(dev, &dp->d_slice));
}
SYSCTL_INT(_debug_sizeof, OID_AUTO, disklabel, CTLFLAG_RD,
0, sizeof(struct disklabel), "sizeof(struct disklabel)");
SYSCTL_INT(_debug_sizeof, OID_AUTO, diskslices, CTLFLAG_RD,
0, sizeof(struct diskslices), "sizeof(struct diskslices)");
SYSCTL_INT(_debug_sizeof, OID_AUTO, disk, CTLFLAG_RD,
0, sizeof(struct disk), "sizeof(struct disk)");
#endif /* NO_GEOM */
/*-
* Disk error is the preface to plaintive error messages
* about failing disk transfers. It prints messages of the form
* "hp0g: BLABLABLA cmd=read fsbn 12345 of 12344-12347"
* blkdone should be -1 if the position of the error is unknown.
* The message is printed with printf.
*/
void
disk_err(struct bio *bp, const char *what, int blkdone, int nl)
{
daddr_t sn;
printf("%s: %s ", devtoname(bp->bio_dev), what);
switch(bp->bio_cmd) {
case BIO_READ: printf("cmd=read "); break;
case BIO_WRITE: printf("cmd=write "); break;
case BIO_DELETE: printf("cmd=delete "); break;
case BIO_GETATTR: printf("cmd=getattr "); break;
case BIO_SETATTR: printf("cmd=setattr "); break;
default: printf("cmd=%x ", bp->bio_cmd); break;
}
sn = bp->bio_blkno;
if (bp->bio_bcount <= DEV_BSIZE) {
printf("fsbn %jd%s", (intmax_t)sn, nl ? "\n" : "");
return;
}
if (blkdone >= 0) {
sn += blkdone;
printf("fsbn %jd of ", (intmax_t)sn);
}
printf("%jd-%jd", (intmax_t)bp->bio_blkno,
(intmax_t)(bp->bio_blkno + (bp->bio_bcount - 1) / DEV_BSIZE));
if (nl)
printf("\n");
}
/*
* Seek sort for disks.
*
* The buf_queue keep two queues, sorted in ascending block order. The first
* queue holds those requests which are positioned after the current block
* (in the first request); the second, which starts at queue->switch_point,
* holds requests which came in after their block number was passed. Thus
* we implement a one way scan, retracting after reaching the end of the drive
* to the first request on the second queue, at which time it becomes the
* first queue.
*
* A one-way scan is natural because of the way UNIX read-ahead blocks are
* allocated.
*/
void
bioq_disksort(bioq, bp)
struct bio_queue_head *bioq;
struct bio *bp;
{
struct bio *bq;
struct bio *bn;
struct bio *be;
if (!atomic_cmpset_int(&bioq->busy, 0, 1))
panic("Recursing in bioq_disksort()");
be = TAILQ_LAST(&bioq->queue, bio_queue);
/*
* If the queue is empty or we are an
* ordered transaction, then it's easy.
*/
if ((bq = bioq_first(bioq)) == NULL) {
bioq_insert_tail(bioq, bp);
bioq->busy = 0;
return;
} else if (bioq->insert_point != NULL) {
/*
* A certain portion of the list is
* "locked" to preserve ordering, so
* we can only insert after the insert
* point.
*/
bq = bioq->insert_point;
} else {
/*
* If we lie before the last removed (currently active)
* request, and are not inserting ourselves into the
* "locked" portion of the list, then we must add ourselves
* to the second request list.
*/
if (bp->bio_pblkno < bioq->last_pblkno) {
bq = bioq->switch_point;
/*
* If we are starting a new secondary list,
* then it's easy.
*/
if (bq == NULL) {
bioq->switch_point = bp;
bioq_insert_tail(bioq, bp);
bioq->busy = 0;
return;
}
/*
* If we lie ahead of the current switch point,
* insert us before the switch point and move
* the switch point.
*/
if (bp->bio_pblkno < bq->bio_pblkno) {
bioq->switch_point = bp;
TAILQ_INSERT_BEFORE(bq, bp, bio_queue);
bioq->busy = 0;
return;
}
} else {
if (bioq->switch_point != NULL)
be = TAILQ_PREV(bioq->switch_point,
bio_queue, bio_queue);
/*
* If we lie between last_pblkno and bq,
* insert before bq.
*/
if (bp->bio_pblkno < bq->bio_pblkno) {
TAILQ_INSERT_BEFORE(bq, bp, bio_queue);
bioq->busy = 0;
return;
}
}
}
/*
* Request is at/after our current position in the list.
* Optimize for sequential I/O by seeing if we go at the tail.
*/
if (bp->bio_pblkno > be->bio_pblkno) {
TAILQ_INSERT_AFTER(&bioq->queue, be, bp, bio_queue);
bioq->busy = 0;
return;
}
/* Otherwise, insertion sort */
while ((bn = TAILQ_NEXT(bq, bio_queue)) != NULL) {
/*
* We want to go after the current request if it is the end
* of the first request list, or if the next request is a
* larger cylinder than our request.
*/
if (bn == bioq->switch_point
|| bp->bio_pblkno < bn->bio_pblkno)
break;
bq = bn;
}
TAILQ_INSERT_AFTER(&bioq->queue, bq, bp, bio_queue);
bioq->busy = 0;
}
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