| Message ID | 20171213204611.26276-1-jsnow@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 13/12/2017 21:46, John Snow wrote: > > When a user provides a new speed, kick the job to allow it to recalculate > its delay. > > Signed-off-by: John Snow <jsnow@redhat.com> > --- > > RFC: Why is block_job_mutex shared between all jobs, > instead of being per-job? Because that patch was partly extracted out of a bigger one, and I was both lazy and worried about breaking things close to the release. In other words more uses of the mutex are coming, and it will need to be shared between jobs to work fine with transactions and monitor commands (which don't know the job they're working on until they've looked it up). Starting a paused block job is not a hot path. :) Paolo
On Wed, Dec 13, 2017 at 03:46:11PM -0500, John Snow wrote: > If users set an unreasonably low speed (like one byte per second), the > calculated delay may exceed many hours. While we like to punish users > for asking for stupid things, we do also like to allow users to correct > their wicked ways. > > When a user provides a new speed, kick the job to allow it to recalculate > its delay. > > Signed-off-by: John Snow <jsnow@redhat.com> > --- > > RFC: Why is block_job_mutex shared between all jobs, > instead of being per-job? > > blockjob.c | 30 +++++++++++++++++++++++++++++- > 1 file changed, 29 insertions(+), 1 deletion(-) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
On Wed, Dec 13, 2017 at 03:46:11PM -0500, John Snow wrote: > If users set an unreasonably low speed (like one byte per second), the > calculated delay may exceed many hours. While we like to punish users > for asking for stupid things, we do also like to allow users to correct > their wicked ways. > > When a user provides a new speed, kick the job to allow it to recalculate > its delay. > > Signed-off-by: John Snow <jsnow@redhat.com> > --- > > RFC: Why is block_job_mutex shared between all jobs, > instead of being per-job? > The mutex protects job-specific fields of job->busy and job->sleep_timer, so I think the mutex should be specific to job, not global across all jobs. > blockjob.c | 30 +++++++++++++++++++++++++++++- > 1 file changed, 29 insertions(+), 1 deletion(-) > > diff --git a/blockjob.c b/blockjob.c > index 715c2c2680..6173e4728c 100644 > --- a/blockjob.c > +++ b/blockjob.c > @@ -59,6 +59,7 @@ static void __attribute__((__constructor__)) block_job_init(void) > > static void block_job_event_cancelled(BlockJob *job); > static void block_job_event_completed(BlockJob *job, const char *msg); > +static void block_job_enter_cond(BlockJob *job, bool(*fn)(BlockJob *job)); > > /* Transactional group of block jobs */ > struct BlockJobTxn { > @@ -480,9 +481,16 @@ static void block_job_completed_txn_success(BlockJob *job) > } > } > > +/* Assumes the block_job_mutex is held */ > +static bool block_job_timer_pending(BlockJob *job) > +{ > + return timer_pending(&job->sleep_timer); > +} > + > void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp) > { > Error *local_err = NULL; > + int64_t old_speed = job->speed; > > if (!job->driver->set_speed) { > error_setg(errp, QERR_UNSUPPORTED); > @@ -495,6 +503,12 @@ void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp) > } > > job->speed = speed; > + if (speed <= old_speed) { > + return; > + } > + > + /* kick only if a timer is pending */ > + block_job_enter_cond(job, block_job_timer_pending); > } > > void block_job_complete(BlockJob *job, Error **errp) > @@ -821,7 +835,11 @@ void block_job_resume_all(void) > } > } > > -void block_job_enter(BlockJob *job) > +/* > + * Conditionally enter a block_job pending a call to fn() while > + * under the block_job_lock critical section. > + */ > +static void block_job_enter_cond(BlockJob *job, bool(*fn)(BlockJob *job)) > { > if (!block_job_started(job)) { > return; > @@ -836,6 +854,11 @@ void block_job_enter(BlockJob *job) > return; > } > > + if (fn && !fn(job)) { > + block_job_unlock(); > + return; > + } > + > assert(!job->deferred_to_main_loop); > timer_del(&job->sleep_timer); > job->busy = true; > @@ -843,6 +866,11 @@ void block_job_enter(BlockJob *job) > aio_co_wake(job->co); > } > > +void block_job_enter(BlockJob *job) > +{ > + block_job_enter_cond(job, NULL); > +} > + > bool block_job_is_cancelled(BlockJob *job) > { > return job->cancelled; > -- > 2.14.3 > Thanks, Applied to my block branch: git://github.com/codyprime/qemu-kvm-jtc block -Jeff
diff --git a/blockjob.c b/blockjob.c index 715c2c2680..6173e4728c 100644 --- a/blockjob.c +++ b/blockjob.c @@ -59,6 +59,7 @@ static void __attribute__((__constructor__)) block_job_init(void) static void block_job_event_cancelled(BlockJob *job); static void block_job_event_completed(BlockJob *job, const char *msg); +static void block_job_enter_cond(BlockJob *job, bool(*fn)(BlockJob *job)); /* Transactional group of block jobs */ struct BlockJobTxn { @@ -480,9 +481,16 @@ static void block_job_completed_txn_success(BlockJob *job) } } +/* Assumes the block_job_mutex is held */ +static bool block_job_timer_pending(BlockJob *job) +{ + return timer_pending(&job->sleep_timer); +} + void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp) { Error *local_err = NULL; + int64_t old_speed = job->speed; if (!job->driver->set_speed) { error_setg(errp, QERR_UNSUPPORTED); @@ -495,6 +503,12 @@ void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp) } job->speed = speed; + if (speed <= old_speed) { + return; + } + + /* kick only if a timer is pending */ + block_job_enter_cond(job, block_job_timer_pending); } void block_job_complete(BlockJob *job, Error **errp) @@ -821,7 +835,11 @@ void block_job_resume_all(void) } } -void block_job_enter(BlockJob *job) +/* + * Conditionally enter a block_job pending a call to fn() while + * under the block_job_lock critical section. + */ +static void block_job_enter_cond(BlockJob *job, bool(*fn)(BlockJob *job)) { if (!block_job_started(job)) { return; @@ -836,6 +854,11 @@ void block_job_enter(BlockJob *job) return; } + if (fn && !fn(job)) { + block_job_unlock(); + return; + } + assert(!job->deferred_to_main_loop); timer_del(&job->sleep_timer); job->busy = true; @@ -843,6 +866,11 @@ void block_job_enter(BlockJob *job) aio_co_wake(job->co); } +void block_job_enter(BlockJob *job) +{ + block_job_enter_cond(job, NULL); +} + bool block_job_is_cancelled(BlockJob *job) { return job->cancelled;
If users set an unreasonably low speed (like one byte per second), the calculated delay may exceed many hours. While we like to punish users for asking for stupid things, we do also like to allow users to correct their wicked ways. When a user provides a new speed, kick the job to allow it to recalculate its delay. Signed-off-by: John Snow <jsnow@redhat.com> --- RFC: Why is block_job_mutex shared between all jobs, instead of being per-job? blockjob.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-)