lock computer

The comparison between optimistic lock and pessimistic lock: Category Realize Characteristics Risk Pessimistic lock Rely on the lock mechanism of database layer Exclusive Nature The large overhead of database performance is often unsustainable, especially for

Tag: Code member jdk1.7 read illegal boolean return port OwnerRelease Fair Lock (based on jdk1.7.0_40)1. Unlock ()Unlock () implemented in Reentrantlock.java, the source code is as follows: Public void unlock () { sync.release (1);}Description :Unlock () is an unlock function, which is implemented by Aqs's release () function.Here, the meaning of "1" is the same as the "Get Lock function acquire (1)", wh

"Why do you want to lock?" A database is a shared resource that is used by a multi-user, such as a user table T_user, two people in front of the browser login to the same account, the phone number changed. When multiple users have concurrent access to the data, multiple transactions are generated in the database while the same data is being accessed. If the concurrency operation is not controlled, it may read and store incorrect data, destroy the cons

Mysql lock mechanism usage summary, mysql Lock Mechanism 1. isolation level (1) Read uncommitted (RU) At this isolation level, transactions are completely isolated and dirty reads are generated. uncommitted records can be read, which is not used in actual cases. (2) Read committed (RC) Only committed records can be read. At this isolation level, phantom read occurs. Phantom read refers to executing the same

There are many implementation classes of lock in the Java.util.concurrent.locks package, commonly used in Reentrantlock, Readwritelock (Implementation class Reentrantreadwritelock), Its realization all relies on Java.util.concurrent.AbstractQueuedSynchronizer class, realizes the idea to be similar, therefore we take reentrantlock as the explanation cut-in point. 1. Reentrantlock's call Process After observation Reentrantlock all

freed and rolled back, another transaction gets locked, and the transaction continues to complete. However, in cases involving an external lock or a table lock, the InnoDB does not automatically detect the deadlock, whichNeed to be resolved by setting the lock wait timeout parameter innodb_lock_wait_timeout. It is necessary to note that this parameter is not onl

When InnoDB determines whether a row lock is in conflict, in addition to the most basic is/ix/s/x lock collision judgment, InnoDB also subdivides the lock into the following seed types: Record Lock (RK)Record locks, lock only one row of index records Gap

The lock mechanism is an important feature of a database that is different from the file system and an effective way to manage concurrent access. MySQL locks include table-level locks, page-level locks, and row-level locks. Table-level locks are the most granular locks in MySQL. They are easy to implement and consume less resources. They are supported by most MySQL engines. The most commonly used MYISAM and INNODB support table-level locks. The

feature, consumers will certainly not buy it. The clock of the computer is also this function. The modification time is a small probability event, and the read time is a frequent action. The following code is taken from the 2.4.34 kernel: Listing 5. 2.4.34 seqlock implementation code 443 void do_gettimeofday (struct timeval * TV) 444 {...... 448 read_lock_irqsave ( xtime_lock, flags );...... 455 sec = xtime. TV _sec; 456 USEC + = xtime

Tags: handle dirty \ n Client pre Opera read data reporting requestThe lock in MySQL:Grammar:LOCK Table table Name 1 read| WRITE, table name 2 read| WRITE ... "Lock-up table" ... "..".UNLOCK TABLES "Release table"READ: Reading Lock | Shared Lock: All clients can only read this table and cannot write this tableWrite:

A recently maintained network server encountered performance problems, so it made major changes to the original program framework. Most of the changes are the thread working mode and data transmission mode. The final result is to change the lock usage mode. After some improvement, we can basically achieve GMB Network Adapter working at full speed. In After the performance was up to standard, I was wondering if I could use a more lightweight

Basic concepts In this chapter, we will explain the principle of "thread gain fair lock", and we need to understand several basic concepts before we explain it. The following are all based on these concepts; These concepts may be tedious, but from these concepts it is possible to glimpse some of the architecture of the "Java Lock", which is helpful in understanding the

Pessimistic lock and optimistic lock in hibernate Locking)During the implementation of business logic, data access needs to be exclusive. For example, in the daily final computing process of the financial system, we want to process the data at a cut-off time point instead of the settlement process (which may be several seconds, or several hours), and the data changes again. At this point, we need to use som

Redis Lock Structure and redis lockSingle thread and isolation Redis uses a single thread to execute transactions. transactions are run in a serial manner. That is to say, the execution of a single command in Redis and the execution of a transaction are thread-safe and will not affect each other, isolation. In multi-threaded programming, be careful when accessing shared resources: import threadingnum = 1lock = threading.Lock()def change_num(): glob