Synchronous and asynchronous IO IO difference:

Synchronous and asynchronous IO IO difference:

When synchronization is a function call, until no results, the call will not return. That is one thing to do, such as a front done before doing the next thing.

Asynchronous and synchronous relative, when starting an asynchronous procedure call, the caller can not immediately get results. The actual processing of the call after completion member, to inform the caller via a state, and a notification callback.

Blocking IO features: IO is performed in two stages (waiting for data and copies of data in two stages)

Non-blocking busy polling: data did not come, the process would stop to detect data until data

Obstruction: data did not come, and consequently do not do until the data comes before the next step of the process

Non-blocking IO model advantages: to achieve a service multiple clients at the same time, be able to do other live waiting for task completion time, including the submission of other tasks

Disadvantages: non-stop polling recv, take up more cpu resources

Exception handling correspondence BlockingIOError the CPU cost is invalid

How to solve: IO multiplexing

Multiplexing IO: the socket to the operating system to monitor, find the equivalent of an agent (select) to collect courier. Courier arrives, it notifies the user, the user pick them up.

Blocking I / O blocking only one I / O operation, the I / O model is capable of blocking a plurality of multiplexed I / O operations, so called multiplexing.

Linux is the difference between the root of the home directory:

Linux root directory is the top directory, all files under the root directory, while bin, etc, root, mnt, such as file directory in the root directory, home directory / home user name inside

linux operating system's file system What? What are the characteristics?

ext: first file system specially made for linux core. The maximum limit is unknown single file; the file system capacity up to 2GB.

ext3: a log file system. The largest single file limit 16TB, the file system supports a maximum capacity of 32TB.

ext4;

Theodore Tso led the development team to achieve, the log file system in linux system, the largest single file limit 16TB, the file system supports a maximum capacity of 1EB.

ntfs: Windows2000 later version, it is among a windows system file management system, has better file management and disk management capabilities.

Features: NTFS file system can provide security protection for your computer files, and supports file encryption function;

2.NTFS disk provided with faster, higher compression ratio features

3. NTFS can support a maximum capacity of up to 2TB large hard drive, but with the increasing disk capacity, he is also its performance will not decrease.

4. The user can be given a single file NTFS file system according to their actual computer folders and folders certain rights, greatly improved security and reliability of the operation of the computer;

The files and data transfer time will be faster;

6.NTFS file system has a very low probability of failure, but also has some ability to repair itself.

7. There are very high disk utilization

sqlite3 and mysql difference:

sqlite3 features simple, small, maximize the efficiency of disk, less functional, belongs to the local database, used for reading and writing less, 100w less data, does not support distributed;

mysql full-featured, integrated, concurrent pursuit of maximum efficiency