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<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">dm-cache mq policy: Fast warm-up<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">The multiqueue policy promotes a block only after promote_threshold + 4 (READ_PROMOTE_THRESHOLD) times hit on read I/O. It will be useful if the policy promotes the block
during its first reference in the following use cases.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">1. Storage array has information about which blocks are heavily used and can pass it to server for warming up the cache. (A process running in the server can simply read
those blocks when device is idle).<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">2. Database Application or workload capture tool knows where the hot data is and can promote them before it’s actual use.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">3. To replace a cache device<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">The below patch will allow a block to get promoted during its first reference only if requested by user via dmsetup message. It can be changed to allow based on particular
process or process group also.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">Signed-off-by: Somasundaram, Krishnasamy <Somasundaram.Krishnasamy@netapp.com><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">Reviewed-by: Yanling, Qi <Yanling.Qi@netapp.com><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">---<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">index 7f1aaa3..9653a3c 100644<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">--- a/drivers/md/dm-cache-policy-mq.c<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+++ b/drivers/md/dm-cache-policy-mq.c<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">@@ -390,6 +390,10 @@ struct mq_policy {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> */<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> unsigned promote_threshold;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ /* Allow the blocks to be promoted during first reference itself<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ */<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ unsigned cachefill_enabled;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> /*<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> * The hash table allows us to quickly find an entry by origin<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> * block. Both pre_cache and cache entries are in here.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">@@ -648,6 +652,9 @@ static int demote_cblock(struct mq_policy *mq, dm_oblock_t *oblock)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">static unsigned adjusted_promote_threshold(struct mq_policy *mq,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> bool discarded_oblock, int data_dir)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">{<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ if (mq->cachefill_enabled)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ return 1;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> if (data_dir == READ)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> return mq->promote_threshold + READ_PROMOTE_THRESHOLD;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">@@ -835,7 +842,8 @@ static int map(struct mq_policy *mq, dm_oblock_t oblock,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> if (e && in_cache(mq, e))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> r = cache_entry_found(mq, e, result);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- else if (iot_pattern(&mq->tracker) == PATTERN_SEQUENTIAL)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ else if (iot_pattern(&mq->tracker) == PATTERN_SEQUENTIAL &&<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ !mq->cachefill_enabled)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> result->op = POLICY_MISS;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> else if (e)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">@@ -1134,21 +1142,22 @@ static int mq_set_config_value(struct dm_cache_policy *p,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> const char *key, const char *value)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">{<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> struct mq_policy *mq = to_mq_policy(p);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- enum io_pattern pattern;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> unsigned long tmp;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ if (kstrtoul(value, 10, &tmp))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ return -EINVAL;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> if (!strcasecmp(key, "random_threshold"))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- pattern = PATTERN_RANDOM;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ mq->tracker.thresholds[PATTERN_RANDOM] = tmp;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> else if (!strcasecmp(key, "sequential_threshold"))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- pattern = PATTERN_SEQUENTIAL;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ mq->tracker.thresholds[PATTERN_SEQUENTIAL] = tmp;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ else if (!strcasecmp(key, "enable_cachefill"))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ mq->cachefill_enabled = true;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ else if (!strcasecmp(key, "disable_cachefill"))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ mq->cachefill_enabled = false;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> else<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> return -EINVAL;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- if (kstrtoul(value, 10, &tmp))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- return -EINVAL;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">-<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">- mq->tracker.thresholds[pattern] = tmp;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">-<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> return 0;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">}<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">@@ -1212,6 +1221,7 @@ static struct dm_cache_policy *mq_create(dm_cblock_t cache_size,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> mq->hit_count = 0;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> mq->generation = 0;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> mq->promote_threshold = 0;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New"">+ mq->cachefill_enabled = 0;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> mutex_init(&mq->lock);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""> spin_lock_init(&mq->tick_lock);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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