lightnvm: pblk: add debug stat for read cache hits

Add a new debug counter to measure cache hits on the read path

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-init.c

@@ -839,6 +839,7 @@ static void *pblk_init(struct nvm_tgt_dev *dev, struct gendisk *tdisk,
 	atomic_long_set(&pblk->sync_writes, 0);
 	atomic_long_set(&pblk->compl_writes, 0);
 	atomic_long_set(&pblk->inflight_reads, 0);
+	atomic_long_set(&pblk->cache_reads, 0);
 	atomic_long_set(&pblk->sync_reads, 0);
 	atomic_long_set(&pblk->recov_writes, 0);
 	atomic_long_set(&pblk->recov_writes, 0);

drivers/lightnvm/pblk-read.c

@@ -76,6 +76,9 @@ retry:
 			}
 			WARN_ON(test_and_set_bit(i, read_bitmap));
 			advanced_bio = 1;
+#ifdef CONFIG_NVM_DEBUG
+			atomic_long_inc(&pblk->cache_reads);
+#endif
 		} else {
 			/* Read from media non-cached sectors */
 			rqd->ppa_list[j++] = p;
@@ -280,6 +283,9 @@ retry:
 			goto retry;
 		}
 		WARN_ON(test_and_set_bit(0, read_bitmap));
+#ifdef CONFIG_NVM_DEBUG
+			atomic_long_inc(&pblk->cache_reads);
+#endif
 	} else {
 		rqd->ppa_addr = ppa;
 	}

drivers/lightnvm/pblk-sysfs.c

@@ -294,7 +294,7 @@ static ssize_t pblk_sysfs_lines_info(struct pblk *pblk, char *page)
 static ssize_t pblk_sysfs_stats_debug(struct pblk *pblk, char *page)
 {
 	return snprintf(page, PAGE_SIZE,
-		"%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\n",
+		"%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\n",
 			atomic_long_read(&pblk->inflight_writes),
 			atomic_long_read(&pblk->inflight_reads),
 			atomic_long_read(&pblk->req_writes),
@@ -307,6 +307,7 @@ static ssize_t pblk_sysfs_stats_debug(struct pblk *pblk, char *page)
 			atomic_long_read(&pblk->recov_writes),
 			atomic_long_read(&pblk->recov_gc_writes),
 			atomic_long_read(&pblk->recov_gc_reads),
+			atomic_long_read(&pblk->cache_reads),
 			atomic_long_read(&pblk->sync_reads));
 }
 #endif

drivers/lightnvm/pblk.h

@@ -513,6 +513,7 @@ struct pblk {
 	atomic_long_t sync_writes;	/* Sectors synced to media */
 	atomic_long_t compl_writes;	/* Sectors completed in write bio */
 	atomic_long_t inflight_reads;	/* Inflight sector read requests */
+	atomic_long_t cache_reads;	/* Read requests that hit the cache */
 	atomic_long_t sync_reads;	/* Completed sector read requests */
 	atomic_long_t recov_writes;	/* Sectors submitted from recovery */
 	atomic_long_t recov_gc_writes;	/* Sectors submitted from write GC */