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dm cache background tracker: limit amount of background work that may be issued at once

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On large systems the cache policy can be over enthusiastic and queue far
too much dirty data to be written back.  This consumes memory.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2017-11-08 06:41:43 -05:00 committed by Mike Snitzer
parent deb71918ae
commit 64748b1645
1 changed files with 12 additions and 6 deletions
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18
drivers/md/dm-cache-background-tracker.c
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@ -161,8 +161,17 @@ EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);
static bool max_work_reached(struct background_tracker *b)
{
// FIXME: finish
return false;
return atomic_read(&b->pending_promotes) +
atomic_read(&b->pending_writebacks) +
atomic_read(&b->pending_demotes) >= b->max_work;
}
struct bt_work *alloc_work(struct background_tracker *b)
{
if (max_work_reached(b))
return NULL;
return kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
}
int btracker_queue(struct background_tracker *b,
@ -174,10 +183,7 @@ int btracker_queue(struct background_tracker *b,
if (pwork)
*pwork = NULL;
if (max_work_reached(b))
return -ENOMEM;
w = kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
w = alloc_work(b);
if (!w)
return -ENOMEM;