mmc: fix async request mechanism for sequential read scenarios
When current request is running on the bus and if next request fetched
by mmcqd is NULL, mmc context (mmcqd thread) gets blocked until the
current request completes. This means that if new request comes in while
the mmcqd thread is blocked, this new request can not be prepared in
parallel to current ongoing request. This may result in delaying the new
request execution and increase it's latency.
This change allows to wake up the MMC thread on new request arrival.
Now once the MMC thread is woken up, a new request can be fetched and
prepared in parallel to the current running request which means this new
request can be started immediately after the current running request
completes.
With this change read throughput is improved by 16%.
Change-Id: I8d74fda719c89a710330807c9d8994d40c885aa0
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 6c43ec7..6982c45 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -155,6 +155,22 @@
int (*err_check) (struct mmc_card *, struct mmc_async_req *);
};
+/**
+ * mmc_context_info - synchronization details for mmc context
+ * @is_done_rcv wake up reason was done request
+ * @is_new_req wake up reason was new request
+ * @is_waiting_last_req mmc context waiting for single running request
+ * @wait wait queue
+ * @lock lock to protect data fields
+ */
+struct mmc_context_info {
+ bool is_done_rcv;
+ bool is_new_req;
+ bool is_waiting_last_req;
+ wait_queue_head_t wait;
+ spinlock_t lock;
+};
+
struct mmc_hotplug {
unsigned int irq;
void *handler_priv;
@@ -327,6 +343,7 @@
struct dentry *debugfs_root;
struct mmc_async_req *areq; /* active async req */
+ struct mmc_context_info context_info; /* async synchronization info */
#ifdef CONFIG_FAIL_MMC_REQUEST
struct fault_attr fail_mmc_request;