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Rework syncer termination code:

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Speed up the syncer when shutting down by sleeping for a shorter
    period of time instead of cranking up rushjob and using the
    normal one second sleep.

    Skip empty worklist slots when shutting down to avoid lengthy
    intervals of inactivity.

    Give I/O more time to complete between steps by not speeding the
    syncer quite as much.

    Terminate the syncer after one full pass through the worklist
    plus one second with the worklist containing nothing but syncer
    vnodes.

    Print an indication of shutdown progress to the console.

Add a sysctl, vfs.worklist_len, to allow the size of the syncer worklist
to be monitored.
This commit is contained in:
Don Lewis 2004-07-05 01:07:33 +00:00
parent f1aeae1b95
commit faf1b66d1d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=131602
1 changed files with 79 additions and 33 deletions
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112
sys/kern/vfs_subr.c
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@ -204,7 +204,7 @@ static struct synclist *syncer_workitem_pending;
* vp->v_synclist
* sync_vnode_count
* syncer_delayno
* syncer_shutdown_iter
* syncer_state
* syncer_workitem_pending
* syncer_worklist_len
* rushjob
@ -225,19 +225,13 @@ static int stat_rush_requests; /* number of times I/O speeded up */
SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW, &stat_rush_requests, 0, "");
/*
* Tell the syncer to make three passes through the work list before
* shutting down (unless it runs out of work and shuts down sooner).
*
* Run at 8 times normal speed when shutting down the syncer. With
* the default settings, the syncer will take approximately 12
* seconds to shut down, which is less than the default 60 timeout
* in kproc_shutdown().
* When shutting down the syncer, run it at four times normal speed.
*/
#define SYNCER_SHUTDOWN_ITER_LIMIT (3*SYNCER_MAXDELAY)
#define SYNCER_SHUTDOWN_SPEEDUP 7
#define SYNCER_SHUTDOWN_SPEEDUP 4
static int sync_vnode_count;
static int syncer_shutdown_iter;
static int syncer_worklist_len;
static enum { SYNCER_RUNNING, SYNCER_SHUTTING_DOWN, SYNCER_FINAL_DELAY }
syncer_state;
/*
* Number of vnodes we want to exist at any one time. This is mostly used
@ -1495,6 +1489,21 @@ vn_syncer_add_to_worklist(struct vnode *vp, int delay)
mtx_unlock(&sync_mtx);
}
static int
sysctl_vfs_worklist_len(SYSCTL_HANDLER_ARGS)
{
int error, len;
mtx_lock(&sync_mtx);
len = syncer_worklist_len - sync_vnode_count;
mtx_unlock(&sync_mtx);
error = SYSCTL_OUT(req, &len, sizeof(len));
return (error);
}
SYSCTL_PROC(_vfs, OID_AUTO, worklist_len, CTLTYPE_INT | CTLFLAG_RD, NULL, 0,
sysctl_vfs_worklist_len, "I", "Syncer thread worklist length");
struct proc *updateproc;
static void sched_sync(void);
static struct kproc_desc up_kp = {
@ -1516,39 +1525,71 @@ sched_sync(void)
struct mount *mp;
long starttime;
struct thread *td = FIRST_THREAD_IN_PROC(updateproc);
static int dummychan;
int last_work_seen;
int net_worklist_len;
int syncer_final_iter;
mtx_lock(&Giant);
last_work_seen = -1;
syncer_final_iter = 0;
syncer_state = SYNCER_RUNNING;
starttime = time_second;
EVENTHANDLER_REGISTER(shutdown_pre_sync, syncer_shutdown, td->td_proc,
SHUTDOWN_PRI_LAST);
for (;;) {
mtx_lock(&sync_mtx);
/*
* Make one more full pass through the work list after
* the only vnodes remaining on the work list are the
* syncer vnodes.
*/
if (syncer_shutdown_iter > SYNCER_MAXDELAY &&
syncer_worklist_len == sync_vnode_count)
syncer_shutdown_iter = SYNCER_MAXDELAY;
if (syncer_shutdown_iter == 0) {
if (syncer_state == SYNCER_FINAL_DELAY &&
syncer_final_iter == 0) {
mtx_unlock(&sync_mtx);
kthread_suspend_check(td->td_proc);
mtx_lock(&sync_mtx);
}
net_worklist_len = syncer_worklist_len - sync_vnode_count;
if (syncer_state != SYNCER_RUNNING && starttime != time_second)
printf("%d ", net_worklist_len);
starttime = time_second;
/*
* Push files whose dirty time has expired. Be careful
* of interrupt race on slp queue.
*
* Skip over empty worklist slots when shutting down.
*/
slp = &syncer_workitem_pending[syncer_delayno];
syncer_delayno += 1;
if (syncer_delayno == syncer_maxdelay)
syncer_delayno = 0;
next = &syncer_workitem_pending[syncer_delayno];
do {
slp = &syncer_workitem_pending[syncer_delayno];
syncer_delayno += 1;
if (syncer_delayno == syncer_maxdelay)
syncer_delayno = 0;
next = &syncer_workitem_pending[syncer_delayno];
/*
* If the worklist has wrapped since the
* it was emptied of all but syncer vnodes,
* switch to the FINAL_DELAY state and run
* for one more second.
*/
if (syncer_state == SYNCER_SHUTTING_DOWN &&
net_worklist_len == 0 &&
last_work_seen == syncer_delayno) {
syncer_state = SYNCER_FINAL_DELAY;
syncer_final_iter = SYNCER_SHUTDOWN_SPEEDUP;
}
} while (syncer_state != SYNCER_RUNNING && LIST_EMPTY(slp) &&
syncer_worklist_len > 0);
/*
* Keep track of the last time there was anything
* on the worklist other than syncer vnodes.
* Return to the SHUTTING_DOWN state if any
* new work appears.
*/
if (net_worklist_len > 0) {
last_work_seen = syncer_delayno;
if (syncer_state == SYNCER_FINAL_DELAY)
syncer_state = SYNCER_SHUTTING_DOWN;
}
while ((vp = LIST_FIRST(slp)) != NULL) {
if (VOP_ISLOCKED(vp, NULL) != 0 ||
vn_start_write(vp, &mp, V_NOWAIT) != 0) {
@ -1588,8 +1629,8 @@ sched_sync(void)
VI_UNLOCK(vp);
mtx_lock(&sync_mtx);
}
if (syncer_shutdown_iter > 0)
syncer_shutdown_iter--;
if (syncer_state == SYNCER_FINAL_DELAY && syncer_final_iter > 0)
syncer_final_iter--;
mtx_unlock(&sync_mtx);
/*
@ -1613,10 +1654,13 @@ sched_sync(void)
rushjob -= 1;
mtx_unlock(&sync_mtx);
continue;
} else if (syncer_shutdown_iter > 0)
rushjob = SYNCER_SHUTDOWN_SPEEDUP;
}
mtx_unlock(&sync_mtx);
/*
* Just sleep for a short period if time between
* iterations when shutting down to allow some I/O
* to happen.
*
* If it has taken us less than a second to process the
* current work, then wait. Otherwise start right over
* again. We can still lose time if any single round
@ -1624,7 +1668,10 @@ sched_sync(void)
* matter as we are just trying to generally pace the
* filesystem activity.
*/
if (time_second == starttime)
if (syncer_state != SYNCER_RUNNING)
tsleep(&dummychan, PPAUSE, "syncfnl",
hz / SYNCER_SHUTDOWN_SPEEDUP);
else if (time_second == starttime)
tsleep(&lbolt, PPAUSE, "syncer", 0);
}
}
@ -1664,9 +1711,8 @@ syncer_shutdown(void *arg, int howto)
td = FIRST_THREAD_IN_PROC(updateproc);
sleepq_remove(td, &lbolt);
mtx_lock(&sync_mtx);
if (rushjob < SYNCER_SHUTDOWN_SPEEDUP)
rushjob = SYNCER_SHUTDOWN_SPEEDUP;
syncer_shutdown_iter = SYNCER_SHUTDOWN_ITER_LIMIT;
syncer_state = SYNCER_SHUTTING_DOWN;
rushjob = 0;
mtx_unlock(&sync_mtx);
kproc_shutdown(arg, howto);
}