Re: 2.9test9-mm1 and DAO ATAPI cd-burning corrupt

Nick Piggin
2003-11-07T23:13:55Z

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Prakash K. Cheemplavam wrote:

>
> Yes, with this patch, it seems to be like in mm1 again, no more
> stuttering (or at least I can't notice it anymore, as since 2 daysI
> have an LCD), but also the bad stuttering at erase and burn start are
> gone again. So do you have an idea what causes the problem?
>

Getting there, thanks for testing. We'll take the others off the CC
list: the problem is not in Linus' tree. Please try this patch.

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linux-2.6-npiggin/drivers/block/as-iosched.c | 219 +++++++++------------------
1 files changed, 78 insertions(+), 141 deletions(-)

diff -puN drivers/block/as-iosched.c~as-revert2 drivers/block/as-iosched.c
--- linux-2.6/drivers/block/as-iosched.c~as-revert2 2003-11-07 23:59:20.000000000 +1100
+++ linux-2.6-npiggin/drivers/block/as-iosched.c 2003-11-08 00:00:25.000000000 +1100
@@ -70,7 +70,6 @@
/* Bits in as_io_context.state */
enum as_io_states {
AS_TASK_RUNNING=0, /* Process has not exitted */
- AS_TASK_IOSTARTED, /* Process has started some IO */
AS_TASK_IORUNNING, /* Process has completed some IO */
};

@@ -100,14 +99,6 @@ struct as_data {
sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
struct list_head *dispatch; /* driver dispatch queue */
struct list_head *hash; /* request hash */
-
- unsigned long exit_prob; /* probability a task will exit while
- being waited on */
- unsigned long new_ttime_total; /* mean thinktime on new proc */
- unsigned long new_ttime_mean;
- u64 new_seek_total; /* mean seek on new proc */
- sector_t new_seek_mean;
-
unsigned long current_batch_expires;
unsigned long last_check_fifo[2];
int changed_batch; /* 1: waiting for old batch to end */
@@ -195,7 +186,6 @@ static void free_as_io_context(struct as
/* Called when the task exits */
static void exit_as_io_context(struct as_io_context *aic)
{
- WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state));
clear_bit(AS_TASK_RUNNING, &aic->state);
}

@@ -618,15 +608,8 @@ static void as_antic_timeout(unsigned lo
spin_lock_irqsave(q->queue_lock, flags);
if (ad->antic_status == ANTIC_WAIT_REQ
|| ad->antic_status == ANTIC_WAIT_NEXT) {
- struct as_io_context *aic = ad->io_context->aic;
-
ad->antic_status = ANTIC_FINISHED;
kblockd_schedule_work(&ad->antic_work);
-
- if (aic->ttime_samples == 0) {
- /* process anticipated on has exitted or timed out*/
- ad->exit_prob = (7*ad->exit_prob + 256)/8;
- }
}
spin_unlock_irqrestore(q->queue_lock, flags);
}
@@ -640,7 +623,7 @@ static int as_close_req(struct as_data *
unsigned long delay; /* milliseconds */
sector_t last = ad->last_sector[ad->batch_data_dir];
sector_t next = arq->request->sector;
- sector_t delta; /* acceptable close offset (in sectors) */
+ sector_t delta; /* acceptable close offset (in sectors) */

if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
delay = 0;
@@ -657,7 +640,6 @@ static int as_close_req(struct as_data *
return (last - (delta>>1) <= next) && (next <= last + delta);
}

-static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, unsigned long ttime);
/*
* as_can_break_anticipation returns true if we have been anticipating this
* request.
@@ -675,27 +657,9 @@ static int as_can_break_anticipation(str
{
struct io_context *ioc;
struct as_io_context *aic;
- sector_t s;
-
- ioc = ad->io_context;
- BUG_ON(!ioc);
-
- if (arq && ioc == arq->io_context) {
- /* request from same process */
- return 1;
- }

if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, arq)) {
/* close request */
- struct as_io_context *aic = ioc->aic;
- if (aic) {
- unsigned long thinktime;
- spin_lock(&aic->lock);
- thinktime = jiffies - aic->last_end_request;
- aic->last_end_request = jiffies;
- as_update_thinktime(ad, aic, thinktime);
- spin_unlock(&aic->lock);
- }
return 1;
}

@@ -707,14 +671,20 @@ static int as_can_break_anticipation(str
return 1;
}

+ ioc = ad->io_context;
+ BUG_ON(!ioc);
+
+ if (arq && ioc == arq->io_context) {
+ /* request from same process */
+ return 1;
+ }
+
aic = ioc->aic;
if (!aic)
return 0;

if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
/* process anticipated on has exitted */
- if (aic->ttime_samples == 0)
- ad->exit_prob = (7*ad->exit_prob + 256)/8;
return 1;
}

@@ -728,36 +698,27 @@ static int as_can_break_anticipation(str
return 1;
}

- if (aic->ttime_samples == 0) {
- if (ad->new_ttime_mean > ad->antic_expire)
- return 1;
- if (ad->exit_prob > 128)
- return 1;
- } else if (aic->ttime_mean > ad->antic_expire) {
- /* the process thinks too much between requests */
+ if (aic->seek_samples == 0 || aic->ttime_samples == 0) {
+ /*
+ * Process has just started IO. Don't anticipate.
+ * TODO! Must fix this up.
+ */
return 1;
}

- if (!arq)
- return 0;
-
- if (ad->last_sector[REQ_SYNC] < arq->request->sector)
- s = arq->request->sector - ad->last_sector[REQ_SYNC];
- else
- s = ad->last_sector[REQ_SYNC] - arq->request->sector;
+ if (aic->ttime_mean > ad->antic_expire) {
+ /* the process thinks too much between requests */
+ return 1;
+ }

- if (aic->seek_samples == 0) {
- /*
- * Process has just started IO. Use past statistics to
- * guage success possibility
- */
- if (ad->new_seek_mean/2 > s) {
- /* this request is better than what we're expecting */
- return 1;
- }
+ if (arq && aic->seek_samples) {
+ sector_t s;
+ if (ad->last_sector[REQ_SYNC] < arq->request->sector)
+ s = arq->request->sector - ad->last_sector[REQ_SYNC];
+ else
+ s = ad->last_sector[REQ_SYNC] - arq->request->sector;

- } else {
- if (aic->seek_mean/2 > s) {
+ if (aic->seek_mean > (s>>1)) {
/* this request is better than what we're expecting */
return 1;
}
@@ -802,51 +763,12 @@ static int as_can_anticipate(struct as_d
return 1;
}

-static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, unsigned long ttime)
-{
- /* fixed point: 1.0 == 1<<8 */
- if (aic->ttime_samples == 0) {
- ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8;
- ad->new_ttime_mean = ad->new_ttime_total / 256;
-
- ad->exit_prob = (7*ad->exit_prob)/8;
- }
- aic->ttime_samples = (7*aic->ttime_samples + 256) / 8;
- aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8;
- aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples;
-}
-
-static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, sector_t sdist)
-{
- u64 total;
-
- if (aic->seek_samples == 0) {
- ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8;
- ad->new_seek_mean = ad->new_seek_total / 256;
- }
-
- /*
- * Don't allow the seek distance to get too large from the
- * odd fragment, pagein, etc
- */
- if (aic->seek_samples <= 60) /* second&third seek */
- sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024);
- else
- sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64);
-
- aic->seek_samples = (7*aic->seek_samples + 256) / 8;
- aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8;
- total = aic->seek_total + (aic->seek_samples/2);
- do_div(total, aic->seek_samples);
- aic->seek_mean = (sector_t)total;
-}
-
/*
* as_update_iohist keeps a decaying histogram of IO thinktimes, and
* updates @aic->ttime_mean based on that. It is called when a new
* request is queued.
*/
-static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, struct request *rq)
+static void as_update_iohist(struct as_io_context *aic, struct request *rq)
{
struct as_rq *arq = RQ_DATA(rq);
int data_dir = arq->is_sync;
@@ -857,29 +779,60 @@ static void as_update_iohist(struct as_d
return;

if (data_dir == REQ_SYNC) {
- unsigned long in_flight = atomic_read(&aic->nr_queued)
- + atomic_read(&aic->nr_dispatched);
spin_lock(&aic->lock);
- if (test_bit(AS_TASK_IORUNNING, &aic->state) ||
- test_bit(AS_TASK_IOSTARTED, &aic->state)) {
+
+ if (test_bit(AS_TASK_IORUNNING, &aic->state)
+ && !atomic_read(&aic->nr_queued)
+ && !atomic_read(&aic->nr_dispatched)) {
/* Calculate read -> read thinktime */
- if (test_bit(AS_TASK_IORUNNING, &aic->state)
- && in_flight == 0) {
- thinktime = jiffies - aic->last_end_request;
- thinktime = min(thinktime, MAX_THINKTIME-1);
- } else
- thinktime = 0;
- as_update_thinktime(ad, aic, thinktime);
-
- /* Calculate read -> read seek distance */
- if (aic->last_request_pos < rq->sector)
- seek_dist = rq->sector - aic->last_request_pos;
- else
- seek_dist = aic->last_request_pos - rq->sector;
- as_update_seekdist(ad, aic, seek_dist);
- }
+ thinktime = jiffies - aic->last_end_request;
+ thinktime = min(thinktime, MAX_THINKTIME-1);
+ /* fixed point: 1.0 == 1<<8 */
+ aic->ttime_samples += 256;
+ aic->ttime_total += 256*thinktime;
+ if (aic->ttime_samples)
+ /* fixed point factor is cancelled here */
+ aic->ttime_mean = (aic->ttime_total + 128)
+ / aic->ttime_samples;
+ aic->ttime_samples = (aic->ttime_samples>>1)
+ + (aic->ttime_samples>>2);
+ aic->ttime_total = (aic->ttime_total>>1)
+ + (aic->ttime_total>>2);
+ }
+
+ /* Calculate read -> read seek distance */
+ if (!aic->seek_samples)
+ seek_dist = 0;
+ else if (aic->last_request_pos < rq->sector)
+ seek_dist = rq->sector - aic->last_request_pos;
+ else
+ seek_dist = aic->last_request_pos - rq->sector;
+
aic->last_request_pos = rq->sector + rq->nr_sectors;
- set_bit(AS_TASK_IOSTARTED, &aic->state);
+
+ /*
+ * Don't allow the seek distance to get too large from the
+ * odd fragment, pagein, etc
+ */
+ if (aic->seek_samples < 400) /* second&third seek */
+ seek_dist = min(seek_dist, (aic->seek_mean * 4)
+ + 2*1024*1024);
+ else
+ seek_dist = min(seek_dist, (aic->seek_mean * 4)
+ + 2*1024*64);
+
+ aic->seek_samples += 256;
+ aic->seek_total += (u64)256*seek_dist;
+ if (aic->seek_samples) {
+ u64 total = aic->seek_total + (aic->seek_samples>>1);
+ do_div(total, aic->seek_samples);
+ aic->seek_mean = (sector_t)total;
+ }
+ aic->seek_samples = (aic->seek_samples>>1)
+ + (aic->seek_samples>>2);
+ aic->seek_total = (aic->seek_total>>1)
+ + (aic->seek_total>>2);
+
spin_unlock(&aic->lock);
}
}
@@ -1426,8 +1379,8 @@ static void as_add_request(struct as_dat
arq->io_context = as_get_io_context();

if (arq->io_context) {
- as_update_iohist(ad, arq->io_context->aic, arq->request);
atomic_inc(&arq->io_context->aic->nr_queued);
+ as_update_iohist(arq->io_context->aic, arq->request);
}

alias = as_add_arq_rb(ad, arq);
@@ -1933,17 +1886,6 @@ as_var_store(unsigned long *var, const c
return count;
}

-static ssize_t as_est_show(struct as_data *ad, char *page)
-{
- int pos = 0;
-
- pos += sprintf(page+pos, "%lu %% exit probability\n", 100*ad->exit_prob/256);
- pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean);
- pos += sprintf(page+pos, "%llu sectors new seek distance\n", (unsigned long long)ad->new_seek_mean);
-
- return pos;
-}
-
#define SHOW_FUNCTION(__FUNC, __VAR) \
static ssize_t __FUNC(struct as_data *ad, char *page) \
{ \
@@ -1975,10 +1917,6 @@ STORE_FUNCTION(as_write_batchexpire_stor
&ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
#undef STORE_FUNCTION

-static struct as_fs_entry as_est_entry = {
- .attr = {.name = "est_time", .mode = S_IRUGO },
- .show = as_est_show,
-};
static struct as_fs_entry as_readexpire_entry = {
.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
.show = as_readexpire_show,
@@ -2006,7 +1944,6 @@ static struct as_fs_entry as_write_batch
};

static struct attribute *default_attrs[] = {
- &as_est_entry.attr,
&as_readexpire_entry.attr,
&as_writeexpire_entry.attr,
&as_anticexpire_entry.attr,

_