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dm cache: simplify the IDLE vs BUSY state calculation

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Drop the MODERATE state since it wasn't buying us much.

Also, in check_migrations(), prepare for the next commit ("dm cache
policy smq: don't do any writebacks unless IDLE") by deferring to the
policy to make the final decision on whether writebacks can be
serviced.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2017-05-11 09:07:16 -04:00 committed by Mike Snitzer
parent 701e03e4e1
commit 49b7f76890
1 changed files with 3 additions and 6 deletions
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9
drivers/md/dm-cache-target.c
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@ -1718,7 +1718,6 @@ static int invalidate_start(struct cache *cache, dm_cblock_t cblock,
enum busy {
IDLE,
MODERATE,
BUSY
};
@ -1728,10 +1727,10 @@ static enum busy spare_migration_bandwidth(struct cache *cache)
sector_t current_volume = (atomic_read(&cache->nr_io_migrations) + 1) *
cache->sectors_per_block;
if (current_volume <= cache->migration_threshold)
return idle ? IDLE : MODERATE;
if (idle && current_volume <= cache->migration_threshold)
return IDLE;
else
return idle ? MODERATE : BUSY;
return BUSY;
}
static void inc_hit_counter(struct cache *cache, struct bio *bio)
@ -2047,8 +2046,6 @@ static void check_migrations(struct work_struct *ws)
for (;;) {
b = spare_migration_bandwidth(cache);
if (b == BUSY)
break;
r = policy_get_background_work(cache->policy, b == IDLE, &op);
if (r == -ENODATA)