Transactional lock elision with delayed lock checking

• US 9,460,145 B2
• Filed: 03/26/2013
• Issued: 10/04/2016
• Est. Priority Date: 03/26/2013
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Michael, Maged M., Mitran, Marcel, Ohmacht, Martin, Wang, Kai-Ting Amy
• Primary Examiner(s): Perveen, Rehana
• Assistant Examiner(s): Tran, Loc
• Application Number:
  US13/850,408
• Publication Number:
  US 20140297610A1
• Time in Patent Office: 1,288 Days
• Field of Search: 707/703, 707/704, 707/609
• US Class Current: 1/1
• CPC Class Codes: G06F 12/1475 in a virtual system, e.g. with translation means
• CPC Class Codes: G06F 16/2343 Locking methods, e.g. distributed locking or locking implementation details
• CPC Class Codes: G06F 2212/1052 Security improvement
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0637 Permissions
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 9/466 Transaction processing
• CPC Class Codes: G06F 9/467 Transactional memory G06F9/528 takes precedence
• CPC Class Codes: G06F 9/524 Deadlock detection or avoidance

Abstract

Avoiding data conflicts includes initiating a transactional lock elision transaction containing a critical section, executing the transactional lock elision transaction including the critical section, and checking a status of a lock prior to a commit point in the transactional lock elision transaction executing, wherein the checking the status occurs after processing the critical section. A determination of whether the status of the lock checked is free is made and, responsive to a determination the lock checked is free, a result of the transactional lock elision transaction is committed.

Claims

1. A computer program product for transactional lock elision, the computer program product comprising:

a computer readable hardware storage device containing computer executable program code stored thereon, the computer executable program code comprising;

computer executable program code for initiating a transactional lock elision transaction containing a critical section;

computer executable program code for executing the transactional lock elision transaction including the critical section;

computer executable program code for checking a status of a lock prior to a commit point in the transactional lock elision transaction executing, wherein the checking the status occurs after processing the critical section;

computer executable program code for determining whether the status of the lock checked is free;

computer executable program code responsive to a determination the lock checked is free, for committing a result of the transactional lock elision transaction;

computer executable program code for calculating a cost associated with checking the lock;

computer executable program code for analyzing the cost using an expression of Probability(lock_read_early/late_by_THREAD1

collides_with_lock_held_by_THREAD2)*(overhead_failing_TLE_transaction+wasted_work_done_inside_TLE_transaction); and

computer executable program code for identifying one of a lock read early or a lock read late using a result of the cost analyzing.

2. The computer program product of claim 1 wherein

computer executable program code responsive to a determination the lock checked is not free, further comprises computer executable program code for selecting an action from a set of alternate actions.

3. The computer program product of claim 2, wherein the set of alternate actions comprises computer executable program code for actions including performing a short spin loop and performing a wait-notify.

4. The computer program product of claim 2, further comprising:

computer executable program code for performing at least one alternate action selected from the set of alternate actions.

5. The computer program product of claim 1, further comprising:

computer executable program code for storing results of the identifying one of a lock read early or a lock read late using a result of the cost analyzing into a database; and

computer executable program code for using the results stored to guide and adapt subsequent runs of a same or similar transaction.

6. The computer program product of claim 1, wherein a time window from reading the lock early to a commit time is greater than a time window from reading the lock late to the commit time, wherein a probability of conflict on the lock in deferred locking is less than the probability of conflict on the lock in conventional locking.

7. An apparatus for transactional lock elision, comprising:

a hardware processor unit connected to a communications fabric, wherein the processor unit executes computer executable program code to direct the apparatus to;

initiate a transactional lock elision transaction containing a critical section;

execute the transactional lock elision transaction including the critical section;

check a status of a lock prior to a commit point in the transactional lock elision transaction executing, wherein the checking the status occurs after processing the critical section;

determine whether the status of the lock checked is free;

response to a determination the lock checked is free, commit a result of the transactional lock elision transaction;

calculate a cost associated with checking the lock;

analyze the cost using an expression of

Probability(lock_read_early/late_by_THREAD1 collides_with_lock_held_by_THREAD2)*(overhead_failing_TLE_transaction+wasted_work_done_inside_TLE_transaction);

and identify one of a lock read early or a lock read late using result of the cost analyzing.

8. The apparatus of claim 7 wherein

the processor unit executes the computer executable program code responsive to a determination the lock checked is not free, further directs the apparatus to select an action from a set of alternate actions.

9. The apparatus of claim 8, wherein

the set of alternate actions comprises actions including performing a short spin loop and performing a wait-notify.

10. The apparatus of claim 7, wherein

the processor unit executes the computer executable program code to further direct the apparatus to:

store results of the identifying one of a lock read early or a lock read late using a result of the cost analyzing into a database; and

use the results stored to guide and adapt subsequent runs of a same or similar transaction.

11. The apparatus of claim 7, wherein

a time window from reading the lock early to a commit time is greater than a time window from reading the lock late, wherein a probability of conflict on the lock in deferred locking is less than the probability of conflict on the lock in conventional locking.