ieee1394: shrink tlabel pools, remove tpool semaphores

This patch reduces the size of struct hpsb_host and also removes
semaphores from ieee1394_transactions.c.  On i386, struct hpsb_host
shrinks from 10656 bytes to 6688 bytes.  This is accomplished by
 - using a single wait_queue for hpsb_get_tlabel instead of many
   instances of semaphores,
 - using a single lock to serialize access to all tlabel pools (the
   protected code regions are small, i.e. lock contention very low),
 - omitting the sysfs attribute tlabels_allocations.

Drawback:  In the rare case that a process needs to sleep because all
transaction labels for the node are temporarily exhausted, it is also
woken up if a tlabel for a different node became free, checks for an
available tlabel, and is put to sleep again.  The check is not costly
and the situation occurs extremely rarely.  (Tlabels are typically
only exhausted if there was no context switch to the khpsbpkt thread
which recycles tlables.)  Therefore the benefit of reduced tpool size
outweighs this drawback.

The sysfs attributes tlabels_free and tlabels_mask are not compiled
anymore unless CONFIG_IEEE1394_VERBOSEDEBUG is set.

The by far biggest member of struct hpsb_host, the struct csr_control
csr (5272 bytes on i386), is now placed at the end of struct hpsb_host.

Note, hpsb_get_tlabel calls the macro wait_event_interruptible with a
condition argument which has a side effect (allocation of a tlabel and
manipulation of the packet).  This side effect happens only if the
condition is true.  The patch relies on wait_event_interruptible not
evaluating the condition again after it became true.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 8 insertions, 11 deletions

diff --git a/drivers/ieee1394/hosts.h b/drivers/ieee1394/hosts.h
index 69a7c9f..bc6dbfa 100644
--- a/drivers/ieee1394/hosts.h
+++ b/drivers/ieee1394/hosts.h
@@ -35,7 +35,6 @@ struct hpsb_host {
 	int node_count;      /* number of identified nodes on this bus */
 	int selfid_count;    /* total number of SelfIDs received */
 	int nodes_active;    /* number of nodes with active link layer */
-	u8 speed[ALL_NODES]; /* speed between each node and local node */
 
 	nodeid_t node_id;    /* node ID of this host */
 	nodeid_t irm_id;     /* ID of this bus' isochronous resource manager */
@@ -55,31 +54,29 @@ struct hpsb_host {
 	int reset_retries;
 	quadlet_t *topology_map;
 	u8 *speed_map;
-	struct csr_control csr;
-
-	/* Per node tlabel pool allocation */
-	struct hpsb_tlabel_pool tpool[ALL_NODES];
 
+	int id;
 	struct hpsb_host_driver *driver;
-
 	struct pci_dev *pdev;
-
-	int id;
-
 	struct device device;
 	struct class_device class_dev;
 
 	int update_config_rom;
 	struct work_struct delayed_reset;
-
 	unsigned int config_roms;
 
 	struct list_head addr_space;
 	u64 low_addr_space;	/* upper bound of physical DMA area */
 	u64 middle_addr_space;	/* upper bound of posted write area */
-};
 
+	u8 speed[ALL_NODES];	/* speed between each node and local node */
 
+	/* per node tlabel allocation */
+	u8 next_tl[ALL_NODES];
+	struct { DECLARE_BITMAP(map, 64); } tl_pool[ALL_NODES];
+
+	struct csr_control csr;
+};
 
 enum devctl_cmd {
 	/* Host is requested to reset its bus and cancel all outstanding async