C++博客-快乐的天空-随笔分类-开发笔记

bjam 编译boost

探路者 — Sun, 16 Aug 2015 15:26:00 GMT

link=static variant=debug,release threading=multi runtime-link=static --layout=versioned --toolset=msvc-9.0 --build-type=complete stage
--build-dir= 编译的临时文件会放在builddir里(这样比较好管理，编译完就可以把它删除了)
--stagedir= 存放编译后库文件的路径，默认是stage
--build-type=complete 编译所有版本，不然只会编译一小部分版本（确切地说是相当于:variant=release, threading=multi;link=shared|static;runtime-link=shared）
variant=debug|release 决定编译什么版本(Debug or Release?)
link=static|shared 决定使用静态库还是动态库。
threading=single|multi 决定使用单线程还是多线程库。
runtime-link=static|shared 决定是静态还是动态链接C/C++标准库。
--with- 只编译指定的库，如输入--with-regex就只编译regex库了。
--show-libraries 显示需要编译的库名称

boost库的命名约定：

[lib]-[-mt][-sgdyp]<-boost版本>.<扩展名>

    [lib]：所有模块均采用lib为前缀，除了windows+msvc环境。在windows+msvc环境下，只有静态库(.lib)才有lib前缀，动态库(.dll)没有lib前缀。windows+mingw环境也使用lib前缀。
    ：所有模块均以boost_开头，比如boost_date_time, boost_python等等
    ：比如mgw45, vc90
    [-mt]：多线程支持，不指定则默认为仅支持单线程
    [-sgdyp]：ABI的详细情况
        s 静态链接到C++标准库和运行库
        g 使用debug版的标准库和运行库
        d 编译debug版
        y python相关的debug
        p 使用STLPort作为C++标准库而不是编译器默认提供的
    <-boost版本>：比如-1_45
    <扩展名>：
        windows+mingw：dll(动态库)，dll.a(动态库的导入库)
        windows+msvc：dll(动态库)，lib(无lib前缀的是动态库的导入库)，lib(有lib前缀的是静态库)
        unix/linux：a(静态库)，so(动态库)

使用boost

    windows+msvc编译出来的boost库默认会打开auto-link功能，即在包含boost头文件的时候自动寻找并链接依赖库。这实际上是通过msvc特有的预处理指令#pragma comment(lib, "xxx.lib")来实现的，默认的实现为链接静态库。
        如果想要链接动态库，则需要使用预定义宏 -DBOOST_ALL_DYN_LINK
        如果想要完全手动控制链接方式，则需要使用预定义宏 -DBOOST_ALL_NO_LIB。
    windows+mingw编译出来的boost库不支持auto-link，因为gcc没有类似msvc的#pragma comment预处理指令，所以必须手动控制链接方式。
    asio：依赖Boost.system模块，并且如果用到特定功能还可能依赖Boost.regex, Boost.openssl, Boost.thread, Boost.date_time, Boost.serialization等等，可以使用预定义宏 -DBOOST_DATE_TIME_NO_LIB 以及 -DBOOST_REGEX_NO_LIB 关闭相应模块的自动链接。windows下asio最终使用的是windows系统的socket库:ws2_32.lib，Mswsock.lib.同理，msvc可以通过auto-link自动完成链接，mingw需要手动设置。

使用msvc编译真是有些玄妙：

使用预定义宏BOOST_ALL_DYN_LINK，动态链接：则编译时需要动态链接库导入库system,date_time,regex,执行时需要system,date_time。

使用预定义宏BOOST_ALL_NO_LIB，动态链接：则编译时需要动态链接库导入库system,执行时也只需要system。

使用预定义宏BOOST_ALL_NO_LIB，静态链接：则编译时需要静态库system,执行时不需要system。

使用mingw编译，一切正常：

注意上述几个预定义宏只对msvc有用而对mingw是不起作用的

动态链接：则编译时需要动态链接库导入库system,执行时也只需要system

静态链接：则编译时需要静态库system,执行时不需要system

当然ws2_32, Mswsock总是要指定链接的。

Usage:

Bjam [options] [properties] [install|stage]

install Install headers and compiled library files to the

======= configured locations (below).

在“--prefix=”指定的目录下生成所有头文件

（boost源代码下boost文件夹下所有文件）和指定库文件

--prefix= Install architecture independent files here.

Default; C:\Boost on Win32

Default; /usr/local on Unix. Linux, etc.

--exec-prefix= Install architecture dependent files here.

Default;

--libdir= Install library files here.

Default; /lib

--includedir= Install header files here.

Default; /include

stage Build and install only compiled library files

====== to the stage directory.

在“--stagedir=”指定的目录下生成指定库文件

--stagedir= Install library files here

Default; ./stage

【Other Options】:

--build-type= Build the specified pre-defined set of variations

of the libraries. Note, that which variants get

built depends on what each library supports.

minimal (default) - Builds the single

"release" version of the libraries. This

release corresponds to specifying:

"release multi shared

static shared" as the

Build variant to build.

complete - Attempts to build all possible

variations.

--build-dir=DIR Build in this location instead of building

within the distribution tree. Recommended!

--show-libraries Displays the list of Boost libraries that require

build and installation steps, then exit.

--layout= Determines whether to choose library names

and header locations such that multiple

versions of Boost or multiple compilers can

be used on the same system.

versioned (default) - Names of boost

binaries include the Boost version

number and the name and version of the

compiler. Boost headers are installed

in a subdirectory of whose

name contains the Boost version number.

system - Binaries names do not include

the Boost version number or the name

and version number of the compiler.

Boost headers are installed directly

into . This option is

intended for system integrators who

are building distribution packages.

--buildid=ID Adds the specified ID to the name of built

libraries. The default is to not add anything.

--help This message.

--with- Build and install the specified

If this option is used, only libraries

specified using this option will be built.

--without- Do not build, stage, or install the specified

. By default, all libraries are built.

【Properties】:

toolset=toolset Indicates the toolset to build with.

msvc-6.0 : VC6.0

msvc-7.0: VS2003

msvc-8.0: VS2005

msvc-9.0: VS2008

msvc-10.0: VS2010

variant=debug|release Select the build variant

link=static|shared Whether to build static or shared libraries

threading=single|multi Whether to build single or multithreaded binaries

runtime-link=static|shared Whether to link to static or shared C and C++ runtime.

决定是静态还是动态链接C/C++标准库

compile gce dependence lib

b2 --toolset=msvc-14.0 link=static variant=debug,release threading=multi runtime-link=static asmflags=\safeseh --stagedir=../.. --with-thread --with-atomic --with-coroutine --with-context --with-system --with-regex --with-date_time --with-chrono

[context] msvc /SAFESEH

http://comments.gmane.org/gmane.comp.lib.boost.devel/244402

探路者 2015-08-16 23:26 发表评论

redis 参数配置

探路者 — Wed, 18 Jun 2014 04:57:00 GMT

1. Redis默认不是以守护进程的方式运行，可以通过该配置项修改，使用yes启用守护进程

daemonize no

2. 当Redis以守护进程方式运行时，Redis默认会把pid写入/var/run/redis.pid文件，可以通过pidfile指定

pidfile /var/run/redis.pid

3. 指定Redis监听端口，默认端口为6379，作者在自己的一篇博文中解释了为什么选用6379作为默认端口，因为6379在手机按键上MERZ对应的号码，而MERZ取自意大利歌女Alessia Merz的名字

port 6379

4. 绑定的主机地址

bind 127.0.0.1

5.当客户端闲置多长时间后关闭连接，如果指定为0，表示关闭该功能

timeout 300

6. 指定日志记录级别，Redis总共支持四个级别：debug、verbose、notice、warning，默认为verbose

loglevel verbose

7. 日志记录方式，默认为标准输出，如果配置Redis为守护进程方式运行，而这里又配置为日志记录方式为标准输出，则日志将会发送给/dev/null

logfile stdout

8. 设置数据库的数量，默认数据库为0，可以使用SELECT 命令在连接上指定数据库id

databases 16

9. 指定在多长时间内，有多少次更新操作，就将数据同步到数据文件，可以多个条件配合

save

Redis默认配置文件中提供了三个条件：

save 900 1

save 300 10

save 60 10000

分别表示900秒（15分钟）内有1个更改，300秒（5分钟）内有10个更改以及60秒内有10000个更改。

10. 指定存储至本地数据库时是否压缩数据，默认为yes，Redis采用LZF压缩，如果为了节省CPU时间，可以关闭该选项，但会导致数据库文件变的巨大

rdbcompression yes

11. 指定本地数据库文件名，默认值为dump.rdb

dbfilename dump.rdb

12. 指定本地数据库存放目录

dir ./

13. 设置当本机为slav服务时，设置master服务的IP地址及端口，在Redis启动时，它会自动从master进行数据同步

slaveof

14. 当master服务设置了密码保护时，slav服务连接master的密码

masterauth

15. 设置Redis连接密码，如果配置了连接密码，客户端在连接Redis时需要通过AUTH 命令提供密码，默认关闭

requirepass foobared

16. 设置同一时间最大客户端连接数，默认无限制，Redis可以同时打开的客户端连接数为Redis进程可以打开的最大文件描述符数，如果设置 maxclients 0，表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max number of clients reached错误信息

maxclients 128

17. 指定Redis最大内存限制，Redis在启动时会把数据加载到内存中，达到最大内存后，Redis会先尝试清除已到期或即将到期的Key，当此方法处理后，仍然到达最大内存设置，将无法再进行写入操作，但仍然可以进行读取操作。Redis新的vm机制，会把Key存放内存，Value会存放在swap区

maxmemory

18. 指定是否在每次更新操作后进行日志记录，Redis在默认情况下是异步的把数据写入磁盘，如果不开启，可能会在断电时导致一段时间内的数据丢失。因为 redis本身同步数据文件是按上面save条件来同步的，所以有的数据会在一段时间内只存在于内存中。默认为no

appendonly no

19. 指定更新日志文件名，默认为appendonly.aof

appendfilename appendonly.aof

20. 指定更新日志条件，共有3个可选值：
no：表示等操作系统进行数据缓存同步到磁盘（快）
always：表示每次更新操作后手动调用fsync()将数据写到磁盘（慢，安全）
everysec：表示每秒同步一次（折衷，默认值）

appendfsync everysec

21. 指定是否启用虚拟内存机制，默认值为no，简单的介绍一下，VM机制将数据分页存放，由Redis将访问量较少的页即冷数据swap到磁盘上，访问多的页面由磁盘自动换出到内存中（在后面的文章我会仔细分析Redis的VM机制）

vm-enabled no

22. 虚拟内存文件路径，默认值为/tmp/redis.swap，不可多个Redis实例共享

vm-swap-file /tmp/redis.swap

23. 将所有大于vm-max-memory的数据存入虚拟内存,无论vm-max-memory设置多小,所有索引数据都是内存存储的(Redis的索引数据就是keys),也就是说,当vm-max-memory设置为0的时候,其实是所有value都存在于磁盘。默认值为0

vm-max-memory 0

24. Redis swap文件分成了很多的page，一个对象可以保存在多个page上面，但一个page上不能被多个对象共享，vm-page-size是要根据存储的数据大小来设定的，作者建议如果存储很多小对象，page大小最好设置为32或者64bytes；如果存储很大大对象，则可以使用更大的page，如果不确定，就使用默认值

vm-page-size 32

25. 设置swap文件中的page数量，由于页表（一种表示页面空闲或使用的bitmap）是在放在内存中的，，在磁盘上每8个pages将消耗1byte的内存。

vm-pages 134217728

26. 设置访问swap文件的线程数,最好不要超过机器的核数,如果设置为0,那么所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟。默认值为4

vm-max-threads 4

27. 设置在向客户端应答时，是否把较小的包合并为一个包发送，默认为开启

glueoutputbuf yes

28. 指定在超过一定的数量或者最大的元素超过某一临界值时，采用一种特殊的哈希算法

hash-max-zipmap-entries 64

hash-max-zipmap-value 512

29. 指定是否激活重置哈希，默认为开启（后面在介绍Redis的哈希算法时具体介绍）

activerehashing yes

30. 指定包含其它的配置文件，可以在同一主机上多个Redis实例之间使用同一份配置文件，而同时各个实例又拥有自己的特定配置文件

include /path/to/local.conf

# By default Redis does not run as a daemon. Use 'yes' if you need it.

# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.

#Redis默认不是以守护进程的方式运行，可以通过该配置项修改，使用yes启用守护进程

daemonize no

# When running daemonized, Redis writes a pid file in /var/run/redis.pid by

# default. You can specify a custom pid file location here.

#当 Redis 以守护进程的方式运行的时候，Redis 默认会把 pid 文件放在/var/run/redis.pid

#可配置到其他地址，当运行多个 redis 服务时，需要指定不同的 pid 文件和端口

pidfile /var/run/redis.pid

# Accept connections on the specified port, default is 6379.

# If port 0 is specified Redis will not listen on a TCP socket.

#端口

port 6379

# If you want you can bind a single interface, if the bind option is not

# specified all the interfaces will listen for incoming connections.

#指定Redis可接收请求的IP地址,不设置将处理所有请求,建议生产环境中设置

# bind 127.0.0.1

# Close the connection after a client is idle for N seconds (0 to disable)

#客户端连接的超时时间,单位为秒,超时后会关闭连接

timeout 0

# Set server verbosity to 'debug'

# it can be one of:

# debug (a lot of information, useful for development/testing)

# verbose (many rarely useful info, but not a mess like the debug level)

# notice (moderately verbose, what you want in production probably)

# warning (only very important / critical messages are logged)

#日志记录等级，4个可选值

loglevel notice

# Specify the log file name. Also 'stdout' can be used to force

# Redis to log on the standard output. Note that if you use standard

# output for logging but daemonize, logs will be sent to /dev/null

#配置 log 文件地址,默认打印在命令行终端的窗口上，也可设为/dev/null屏蔽日志、

logfile stdout

# Set the number of databases. The default database is DB 0, you can select

# a different one on a per-connection basis using SELECT where

# dbid is a number between 0 and 'databases'-1

#设置数据库的个数,可以使用 SELECT 命令来切换数据库。

databases 16

#

# Save the DB on disk:

#

# save

#

# Will save the DB if both the given number of seconds and the given

# number of write operations against the DB occurred.

#

# In the example below the behaviour will be to save:

# after 900 sec (15 min) if at least 1 key changed

# after 300 sec (5 min) if at least 10 keys changed

# after 60 sec if at least 10000 keys changed

#

# Note: you can disable saving at all commenting all the "save" lines.

#设置 Redis 进行数据库镜像的频率。保存数据到disk的策略

#900秒之内有1个keys发生变化时

#30秒之内有10个keys发生变化时

#60秒之内有10000个keys发生变化时

save 900 1

save 300 10

save 60 10000

# Compress string objects using LZF when dump .rdb databases?

# For default that's set to 'yes' as it's almost always a win.

# If you want to save some CPU in the saving child set it to 'no' but

# the dataset will likely be bigger if you have compressible values or keys.

#在进行镜像备份时,是否进行压缩

rdbcompression yes

# The filename where to dump the DB

#镜像备份文件的文件名

dbfilename dump.rdb

# The working directory.

#

# The DB will be written inside this directory, with the filename specified

# above using the 'dbfilename' configuration directive.

#

# Also the Append Only File will be created inside this directory.

#

# Note that you must specify a directory here, not a file name.

#数据库镜像备份的文件放置的路径

#路径跟文件名分开配置是因为 Redis 备份时，先会将当前数据库的状态写入到一个临时文件

#等备份完成时，再把该临时文件替换为上面所指定的文件

#而临时文件和上面所配置的备份文件都会放在这个指定的路径当中

#默认值为 ./

dir /var/lib/redis/

# Master-Slave replication. Use slaveof to make a Redis instance a copy of

# another Redis server. Note that the configuration is local to the slave

# so for example it is possible to configure the slave to save the DB with a

# different interval, or to listen to another port, and so on.

#设置该数据库为其他数据库的从数据库

#slaveof 当本机为从服务时，设置主服务的IP及端口

# slaveof

# If the master is password protected (using the "requirepass" configuration

# directive below) it is possible to tell the slave to authenticate before

# starting the replication synchronization process, otherwise the master will

# refuse the slave request.

#指定与主数据库连接时需要的密码验证

#masterauth 当本机为从服务时，设置主服务的连接密码

# masterauth

# When a slave lost the connection with the master, or when the replication

# is still in progress, the slave can act in two different ways:

#

# 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will

# still reply to client requests, possibly with out of data data, or the

# data set may just be empty if this is the first synchronization.

#

# 2) if slave-serve-stale data is set to 'no' the slave will reply with

# an error "SYNC with master in progress" to all the kind of commands

# but to INFO and SLAVEOF.

#当slave丢失与master的连接时，或slave仍然在于master进行数据同步时（未与master保持一致）

#slave可有两种方式来响应客户端请求：

#1)如果 slave-serve-stale-data 设置成 'yes'(默认)，slave仍会响应客户端请求,此时可能会有问题

#2)如果 slave-serve-stale-data 设置成 'no'，slave会返回"SYNC with master in progress"错误信息，但 INFO 和SLAVEOF命令除外。

slave-serve-stale-data yes

# Require clients to issue AUTH before processing any other

# commands. This might be useful in environments in which you do not trust

# others with access to the host running redis-server.

#

# This should stay commented out for backward compatibility and because most

# people do not need auth (e.g. they run their own servers).

#

# Warning: since Redis is pretty fast an outside user can try up to

# 150k passwords per second against a good box. This means that you should

# use a very strong password otherwise it will be very easy to break.

#设置客户端连接后进行任何其他指定前需要使用的密码

#redis速度相当快，一个外部用户在一秒钟进行150K次密码尝试，需指定强大的密码来防止暴力破解

# requirepass foobared

# Set the max number of connected clients at the same time. By default there

# is no limit, and it's up to the number of file descriptors the Redis process

# is able to open. The special value '0' means no limits.

# Once the limit is reached Redis will close all the new connections sending

# an error 'max number of clients reached'.

#限制同时连接的客户数量。

#当连接数超过这个值时，redis 将不再接收其他连接请求，客户端尝试连接时将收到 error 信息

# maxclients 128

# Don't use more memory than the specified amount of bytes.

# When the memory limit is reached Redis will try to remove keys

# accordingly to the eviction policy selected (see maxmemmory-policy).

#

# If Redis can't remove keys according to the policy, or if the policy is

# set to 'noeviction', Redis will start to reply with errors to commands

# that would use more memory, like SET, LPUSH, and so on, and will continue

# to reply to read-only commands like GET.

#

# This option is usually useful when using Redis as an LRU cache, or to set

# an hard memory limit for an instance (using the 'noeviction' policy).

#

# WARNING: If you have slaves attached to an instance with maxmemory on,

# the size of the output buffers needed to feed the slaves are subtracted

# from the used memory count, so that network problems / resyncs will

# not trigger a loop where keys are evicted, and in turn the output

# buffer of slaves is full with DELs of keys evicted triggering the deletion

# of more keys, and so forth until the database is completely emptied.

#

# In short... if you have slaves attached it is suggested that you set a lower

# limit for maxmemory so that there is some free RAM on the system for slave

# output buffers (but this is not needed if the policy is 'noeviction').

#设置redis能够使用的最大内存。

#达到最大内存设置后，Redis会先尝试清除已到期或即将到期的Key（设置过expire信息的key）

#在删除时,按照过期时间进行删除，最早将要被过期的key将最先被删除

#如果已到期或即将到期的key删光，仍进行set操作，那么将返回错误

#此时redis将不再接收写请求,只接收get请求。

#maxmemory的设置比较适合于把redis当作于类似memcached 的缓存来使用

# maxmemory

# By default Redis asynchronously dumps the dataset on disk. If you can live

# with the idea that the latest records will be lost if something like a crash

# happens this is the preferred way to run Redis. If instead you care a lot

# about your data and don't want to that a single record can get lost you should

# enable the append only mode: when this mode is enabled Redis will append

# every write operation received in the file appendonly.aof. This file will

# be read on startup in order to rebuild the full dataset in memory.

#

# Note that you can have both the async dumps and the append only file if you

# like (you have to comment the "save" statements above to disable the dumps).

# Still if append only mode is enabled Redis will load the data from the

# log file at startup ignoring the dump.rdb file.

#

# IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append

# log file in background when it gets too big.

#redis 默认每次更新操作后会在后台异步的把数据库镜像备份到磁盘，但该备份非常耗时，且备份不宜太频繁

#redis 同步数据文件是按上面save条件来同步的

#如果发生诸如拉闸限电、拔插头等状况,那么将造成比较大范围的数据丢失

#所以redis提供了另外一种更加高效的数据库备份及灾难恢复方式

#开启append only 模式后,redis 将每一次写操作请求都追加到appendonly.aof 文件中

#redis重新启动时,会从该文件恢复出之前的状态。

#但可能会造成 appendonly.aof 文件过大，所以redis支持BGREWRITEAOF 指令，对appendonly.aof重新整理

appendonly no

# The name of the append only file (default: "appendonly.aof")

##更新日志文件名，默认值为appendonly.aof

# appendfilename appendonly.aof

# The fsync() call tells the Operating System to actually write data on disk

# instead to wait for more data in the output buffer. Some OS will really flush

# data on disk, some other OS will just try to do it ASAP.

#

# Redis supports three different modes:

#

# no: don't fsync, just let the OS flush the data when it wants. Faster.

# always: fsync after every write to the append only log . Slow, Safest.

# everysec: fsync only if one second passed since the last fsync. Compromise.

#

# The default is "everysec" that's usually the right compromise between

# speed and data safety. It's up to you to understand if you can relax this to

# "no" that will will let the operating system flush the output buffer when

# it wants, for better performances (but if you can live with the idea of

# some data loss consider the default persistence mode that's snapshotting),

# or on the contrary, use "always" that's very slow but a bit safer than

# everysec.

#

# If unsure, use "everysec".

#设置对 appendonly.aof 文件进行同步的频率

#always 表示每次有写操作都进行同步,everysec 表示对写操作进行累积,每秒同步一次。

#no表示等操作系统进行数据缓存同步到磁盘，都进行同步,everysec 表示对写操作进行累积,每秒同步一次

# appendfsync always

appendfsync everysec

# appendfsync no

# Virtual Memory allows Redis to work with datasets bigger than the actual

# amount of RAM needed to hold the whole dataset in memory.

# In order to do so very used keys are taken in memory while the other keys

# are swapped into a swap file, similarly to what operating systems do

# with memory pages.

#

# To enable VM just set 'vm-enabled' to yes, and set the following three

# VM parameters accordingly to your needs.

#是否开启虚拟内存支持。

#redis 是一个内存数据库，当内存满时,无法接收新的写请求,所以在redis2.0后,提供了虚拟内存的支持

#但需要注意的，redis 所有的key都会放在内存中，在内存不够时,只把value 值放入交换区

#虽使用虚拟内存，但性能基本不受影响，需要注意的是要把vm-max-memory设置到足够来放下所有的key

vm-enabled no

# vm-enabled yes

# This is the path of the Redis swap file. As you can guess, swap files

# can't be shared by different Redis instances, so make sure to use a swap

# file for every redis process you are running. Redis will complain if the

# swap file is already in use.

#

# The best kind of storage for the Redis swap file (that's accessed at random)

# is a Solid State Disk (SSD).

#

# *** WARNING *** if you are using a shared hosting the default of putting

# the swap file under /tmp is not secure. Create a dir with access granted

# only to Redis user and configure Redis to create the swap file there.

#设置虚拟内存的交换文件路径，不可多个Redis实例共享

vm-swap-file /tmp/redis.swap

# vm-max-memory configures the VM to use at max the specified amount of

# RAM. Everything that deos not fit will be swapped on disk *if* possible, that

# is, if there is still enough contiguous space in the swap file.

#

# With vm-max-memory 0 the system will swap everything it can. Not a good

# default, just specify the max amount of RAM you can in bytes, but it's

# better to leave some margin. For instance specify an amount of RAM

# that's more or less between 60 and 80% of your free RAM.

#设置开启虚拟内存后,redis将使用的最大物理内存大小。

#默认为0，redis将把他所有能放到交换文件的都放到交换文件中，以尽量少的使用物理内存

#即当vm-max-memory设置为0的时候,其实是所有value都存在于磁盘

#在生产环境下,需要根据实际情况设置该值,最好不要使用默认的 0

vm-max-memory 0

# Redis swap files is split into pages. An object can be saved using multiple

# contiguous pages, but pages can't be shared between different objects.

# So if your page is too big, small objects swapped out on disk will waste

# a lot of space. If you page is too small, there is less space in the swap

# file (assuming you configured the same number of total swap file pages).

#

# If you use a lot of small objects, use a page size of 64 or 32 bytes.

# If you use a lot of big objects, use a bigger page size.

# If unsure, use the default :)

#设置虚拟内存的页大小

如果 value 值比较大,如要在 value 中放置博客、新闻之类的所有文章内容，就设大一点

vm-page-size 32

# Number of total memory pages in the swap file.

# Given that the page table (a bitmap of free/used pages) is taken in memory,

# every 8 pages on disk will consume 1 byte of RAM.

#

# The total swap size is vm-page-size * vm-pages

#

# With the default of 32-bytes memory pages and 134217728 pages Redis will

# use a 4 GB swap file, that will use 16 MB of RAM for the page table.

#

# It's better to use the smallest acceptable value for your application,

# but the default is large in order to work in most conditions.

#设置交换文件的总的 page 数量

#注意page table信息是放在物理内存中，每8个page 就会占据RAM中的 1 个 byte

#总的虚拟内存大小 = vm-page-size * vm-pages

vm-pages 134217728

# Max number of VM I/O threads running at the same time.

# This threads are used to read/write data from/to swap file, since they

# also encode and decode objects from disk to memory or the reverse, a bigger

# number of threads can help with big objects even if they can't help with

# I/O itself as the physical device may not be able to couple with many

# reads/writes operations at the same time.

#

# The special value of 0 turn off threaded I/O and enables the blocking

# Virtual Memory implementation.

#设置 VM IO 同时使用的线程数量。

vm-max-threads 4

# Hashes are encoded in a special way (much more memory efficient) when they

# have at max a given numer of elements, and the biggest element does not

# exceed a given threshold. You can configure this limits with the following

# configuration directives.

#redis 2.0后引入了 hash 数据结构。

#hash 中包含超过指定元素个数并且最大的元素当没有超过临界时，hash 将以zipmap来存储

#zipmap又称为 small hash，可大大减少内存的使用

hash-max-zipmap-entries 512

hash-max-zipmap-value 64

# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in

# order to help rehashing the main Redis hash table (the one mapping top-level

# keys to values). The hash table implementation redis uses (see dict.c)

# performs a lazy rehashing: the more operation you run into an hash table

# that is rhashing, the more rehashing "steps" are performed, so if the

# server is idle the rehashing is never complete and some more memory is used

# by the hash table.

#

# The default is to use this millisecond 10 times every second in order to

# active rehashing the main dictionaries, freeing memory when possible.

#

# If unsure:

# use "activerehashing no" if you have hard latency requirements and it is

# not a good thing in your environment that Redis can reply form time to time

# to queries with 2 milliseconds delay.

#

# use "activerehashing yes" if you don't have such hard requirements but

# want to free memory asap when possible.

#是否重置Hash表

#设置成yes后redis将每100毫秒使用1毫秒CPU时间来对redis的hash表重新hash，可降低内存的使用

#当使用场景有较为严格的实时性需求,不能接受Redis时不时的对请求有2毫秒的延迟的话，把这项配置为no。

#如果没有这么严格的实时性要求,可以设置为 yes,以便能够尽可能快的释放内存

activerehashing yes

Redis官方文档对VM的使用提出了一些建议:

当key很小而value很大时,使用VM的效果会比较好.因为这样节约的内存比较大
当key不小时,可以考虑使用一些非常方法将很大的key变成很大的value,如可将key,value组合成一个新的value
最好使用linux ext3 等对稀疏文件支持比较好的文件系统保存你的swap文件
vm-max-threads参数可设置访问swap文件的线程数，最好不要超过机器的核数；设置为0则所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟,但是对数据完整性有很好的保证

redis数据存储

redis的存储分为内存存储、磁盘存储和log文件三部分，配置文件中有三个参数对其进行配置。

save seconds updates，save配置，指出在多长时间内，有多少次更新操作，就将数据同步到数据文件。可多个条件配合，默认配置了三个条件。
appendonly yes/no ，appendonly配置，指出是否在每次更新操作后进行日志记录，如果不开启，可能会在断电时导致一段时间内的数据丢失。因为redis本身同步数据文件是按上面的save条件来同步的，所以有的数据会在一段时间内只存在于内存中。
appendfsync no/always/everysec ，appendfsync配置，no表示等操作系统进行数据缓存同步到磁盘，always表示每次更新操作后手动调用fsync()将数据写到磁盘，everysec表示每秒同步一次。

探路者 2014-06-18 12:57 发表评论

error C2471

探路者 — Sun, 22 Dec 2013 10:25:00 GMT

error C2471: 无法更新程序数据库“d:/Work/ Project/FBReader/debug/vc90.pdb”

fatal error C1083: 无法打开程序数据库文件:“d:/Work/ Project/FBReader/debug/vc90.pdb”: No such file or directory ..

解决方案：修改项目属性右击项目 --> "属性”

1. “C/C++” --> "常规” -->”调试信息格式” 设置为 “C7 兼容(/Z7)”

2. “C/C++” --> "代码生成” -->”启用字符串池” 设置为 “是(/GF)”

3. “链接器” --> "调试” -->”生成调试信息” 设置为 “是(/DEBUG)”

如图：

探路者 2013-12-22 18:25 发表评论

不要为每一天而后悔

探路者 — Sun, 05 Aug 2012 05:27:00 GMT

事效率绝对非常高，与之前在其它公司的实习经历，以及自己在实验室的研究经历相比，更像是把好几天的事情压缩在一天完成。每个人都在同时处理多个不同的项目，对个人时间管理、项目管理、与他人协作的要求格外高。第一件亟待学习的事情就是制订和执行计划，安排现有任务的轻重缓急。也因此在每天结束时，回顾一天工作，会格外有成就感。在实习结束时，可以自豪的说，没有为任何一天而后悔。
几乎每天都在学习新东西、认识新人的新鲜感和兴奋感。项目和产品所涉及的，往往也包括当前业内最优秀最炙手可热的技术，加上不断变化的金融领域需求，和日趋复杂的项目管理，每天也都要不断的通过询问其他同事、网上学校、内部培训等等渠道尽可能的学习。有些team专注于某项技术，深度发掘；有些team需要用到的技术比较广泛，要在短时间内了解多种流程，多个系统之间相互关系；有些team则更需要熟悉了解业务层的知识。但无论怎样，都需要快速学习能力和协作能力。每天都被鼓励要积极提问，积极思考，最大化利用一切可能的资源，加速学习过程。

探路者 2012-08-05 13:27 发表评论