Commit e678900d authored by Ken Raeburn's avatar Ken Raeburn Committed by Mikulas Patocka
Browse files

dm vdo indexer: reorder uds_request to reduce padding 



Reorder fields and make uds_request_type and uds_zone_message packed,
to squeeze out some space. Use struct_group so the request reset code
no longer needs to care about field order.

On x86_64 this reduces the struct size from 144 to 120, which saves 48
kB (about 12%) per VDO hash zone.

Signed-off-by: default avatarKen Raeburn <raeburn@redhat.com>
Signed-off-by: default avatarMatthew Sakai <msakai@redhat.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent 88f7f56d

drivers/md/dm-vdo/indexer/index-session.c

+1 −5
Original line number Diff line number Diff line
@@ -100,7 +100,6 @@ static int get_index_session(struct uds_index_session *index_session) 


int uds_launch_request(struct uds_request *request)

{

	size_t internal_size;

	int result;



	if (request->callback == NULL) {
@@ -121,10 +120,7 @@ int uds_launch_request(struct uds_request *request) 
	}



	/* Reset all internal fields before processing. */

	internal_size =

		sizeof(struct uds_request) - offsetof(struct uds_request, zone_number);

	// FIXME should be using struct_group for this instead

	memset((char *) request + sizeof(*request) - internal_size, 0, internal_size);

	memset(&request->internal, 0, sizeof(request->internal));



	result = get_index_session(request->session);

	if (result != UDS_SUCCESS)

drivers/md/dm-vdo/indexer/indexer.h

+26 −27
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 


#include <linux/mutex.h>

#include <linux/sched.h>

#include <linux/stddef.h>

#include <linux/types.h>

#include <linux/wait.h>
@@ -73,7 +74,7 @@ enum uds_request_type { 
	/* Remove any mapping for a name. */

	UDS_DELETE,



};

} __packed;



enum uds_open_index_type {

	/* Create a new index. */
@@ -226,7 +227,7 @@ struct uds_zone_message { 
	enum uds_zone_message_type type;

	/* The virtual chapter number to which the message applies */

	u64 virtual_chapter;

};

} __packed;



struct uds_index_session;

struct uds_index;
@@ -253,16 +254,23 @@ struct uds_request { 


	/* The existing data associated with the request name, if any */

	struct uds_record_data old_metadata;

	/* Either UDS_SUCCESS or an error code for the request */

	int status;

	/* True if the record name had an existing entry in the index */

	bool found;

	/* Either UDS_SUCCESS or an error code for the request */

	int status;



	/*

	 * The remaining fields are used internally and should not be altered by clients. The index

	 * relies on zone_number being the first field in this section.

	 */



	/* The remaining fields are used internally and should not be altered by clients. */

	struct_group(internal,

		     /* The virtual chapter containing the record name, if known */

		     u64 virtual_chapter;

		     /* The region of the index containing the record name */

		     enum uds_index_region location;

		     /* If true, process request immediately by waking the worker thread */

		     bool unbatched;

		     /* If true, continue this request before processing newer requests */

		     bool requeued;

		     /* Control message for coordinating between zones */

		     struct uds_zone_message zone_message;

		     /* The number of the zone which will process this request*/

		     unsigned int zone_number;

		     /* A link for adding a request to a lock-free queue */
@@ -271,16 +279,7 @@ struct uds_request { 
		     struct uds_request *next_request;

		     /* A pointer to the index processing this request */

		     struct uds_index *index;

	/* Control message for coordinating between zones */

	struct uds_zone_message zone_message;

	/* If true, process request immediately by waking the worker thread */

	bool unbatched;

	/* If true, continue this request before processing newer requests */

	bool requeued;

	/* The virtual chapter containing the record name, if known */

	u64 virtual_chapter;

	/* The region of the index containing the record name */

	enum uds_index_region location;

		     );

};



/* A session is required for most index operations. */