blocks|key|3984756|text|您可以将syslogd+(至少是rsyslog+)配置为在出现日志消息后不同步日志文件，方法是在配置文件中的日志文件路径前添加一个"-“。这以日志消息可能在崩溃中丢失的危险为代价来提高性能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3984757|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You can configure syslogd (and rsyslog at least) not to sync the log files after a log message by prepending a "-" to the log file path in the configuration file. This speeds up performance at the expense of the danger that log messages could be lost in a crash.

blocks|key|822554|text|有几个选项可以提高syslog性能：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|822555|822556|使用宏优化输出调用|unordered-list-item|822557|822558|int+syslog=+LOG_UPTO(LOG_WARNING)；#定义syslog(a，...)如果((a)+&+LogMask+)+syslog((a)，__VA_ARGS__)+int+main(int+argc，char+**argv)+{+LogMask+=+setlogmask(LOG_UPTO(LOG_WARNING))；...+}|822559|使用宏来过滤syslog调用的一个优点是，整个调用被简化为全局变量上的条件跳转，如果您碰巧有调试调用正在通过其他functions.|822560|setlogmask()转换大型数据集，这将非常有用|822561|822562|setlogmask(LOG_UPTO(LOG_LEVEL))|822563|setlogmask()将通过不记录到/dev/log来优化调用，但程序仍然会调用syslog.conf中用作arguments.|822564|filtering的函数|822565|822566|*.err+/var/日志/消息|822567|“查看details."|822568|configure+syslog的syslog.conf手册页以执行异步或缓冲日志记录|822569|822570|metalog用于缓冲日志输出，并将其按块刷新。据我所知，股票syslog和syslog-ng不能做到这一点。|822571|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|17|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|18|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|19|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|1A|8|@]|9|@]|A|$]]|$1|K|3|L|5|E|7|1B|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1D|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1E|8|@]|9|@]|A|$]]|$1|R|3|S|5|E|7|1F|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1H|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1I|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|E|7|1J|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]|$1|11|3|12|5|6|7|1L|8|@]|9|@]|A|$]]|$1|13|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|14|$]]

There are several options to improve syslog performance:

<ul>
<li>Optimizing out calls with a macro

<pre><code> int LogMask = LOG_UPTO(LOG_WARNING);
 #define syslog(a, ...) if ((a) &amp; LogMask ) syslog((a), __VA_ARGS__)

 int main(int argc, char **argv)
 {
 LogMask = setlogmask(LOG_UPTO(LOG_WARNING));
 ...
 }
</code></pre>

An advantage of using a macro to filter syslog calls is that the entire call is 
reduced to a conditional jump on a global variable, very helpful if you happen to
have DEBUG calls which are translating large datasets through other functions.</li>
<li>setlogmask()

<pre><code>setlogmask(LOG_UPTO(LOG_LEVEL))
</code></pre>

setlogmask() will optimize the call by not logging to /dev/log, but the program will
still call the functions used as arguments.</li>
<li>filtering with syslog.conf

<pre><code> *.err /var/log/messages
</code></pre>

"check out the man page for syslog.conf for details."</li>
<li>configure syslog to do asynchronous or buffered logging

metalog used to buffer log output and flushed it in blocks. stock syslog and syslog-ng
do not do this as far as I know.</li>
</ul>

blocks|key|3139655|text|在开始编写新的守护进程之前，您可以检查syslog-ng是否比普通的旧syslog更快(或者可以配置为更快)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3139656|entityMap|0|LINK|mutability|MUTABLE|url|http://www.balabit.com/network-security/syslog-ng/^0|J|9|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Before embarking in new daemon writing you can check if <a href="http://www.balabit.com/network-security/syslog-ng/" rel="nofollow noreferrer">syslog-ng</a> is faster (or can be configured to be faster) than plain old syslog.

blocks|key|3139866|text|如果您控制日志应用程序的源，您可以使用的一个技巧是在应用程序本身而不是syslog.conf中屏蔽您想要的日志级别。几年前，我用一个应用程序做到了这一点，该应用程序生成了大量的调试日志。我们只是屏蔽了调试级调用，而不是从生产代码中删除调用，而不是将调试级调用发送到后台进程。我实际上找到了代码，它是Perl，但它只是setlogmask(3)调用的前缀。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3139867|use+Sys::Syslog;
#+Start+system+logging
#+setlogmask+controls+what+levels+we're+going+to+let+get+through.++If+we+mask
#+them+off+here,+then+the+syslog+daemon+doesn't+need+to+be+concerned+by+them
#+1+++=+emerg
#+2+++=+alert
#+4+++=+crit
#+8+++=+err
#+16++=+warning
#+32++=+notice
#+64++=+info
#+128+=+debug
Sys::Syslog::setlogsock('unix');
openlog($myname,'pid,cons,nowait','mail');
setlogmask(127);+#+allow+everything+but+debug
#setlogmask(255);+#+everything
syslog('debug',"syslog+opened");|code-block|syntax|javascript|3139868|不知道为什么我用十进制而不是位掩码...耸肩|3139869|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

One trick you can use if you control the source to the logging application is to mask out the log level you want in the app itself, instead of in syslog.conf. I did this years ago with an app that generated a huge, huge, huge amount of debug logs. Rather than remove the calls from the production code, we just masked so that debug level calls never got sent to the daemon. I actually found the code, it's Perl but it's just a front to the setlogmask(3) call.

<pre><code>use Sys::Syslog;
# Start system logging
# setlogmask controls what levels we're going to let get through. If we mask
# them off here, then the syslog daemon doesn't need to be concerned by them
# 1 = emerg
# 2 = alert
# 4 = crit
# 8 = err
# 16 = warning
# 32 = notice
# 64 = info
# 128 = debug
Sys::Syslog::setlogsock('unix');
openlog($myname,'pid,cons,nowait','mail');
setlogmask(127); # allow everything but debug
#setlogmask(255); # everything
syslog('debug',"syslog opened");
</code></pre>

Not sure why I used decimal instead of a bitmask... shrug

blocks|key|822368|text|编写您自己的syslog实现。:-P|type|unstyled|depth|inlineStyleRanges|entityRanges|data|822369|这可以通过两种方式来实现。|822370|822371|编写您自己的LD_PRELOAD钩子来覆盖syslog函数，并将它们输出到stderr。实际上，我在很多年前就写过一篇文章：http://marc.info/?m=97175526803720：-P|ordered-list-item|offset|length|style|CODE|822372|编写自己的syslog守护进程。这只是一个从/dev/log中抓取数据报的简单问题！:-P|822373|822374|好吧，好吧，这两个答案都很有趣。你有没有分析过syslogd，看看它在哪里阻塞得最厉害？|822375|entityMap|0|LINK|mutability|MUTABLE|url|http://marc.info/?m=97175526803720^0|0|0|0|6|A|11|6|1Q|Y|0|0|M|8|0|0|N|7|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|11|8|@$H|12|I|13|J|K]|$H|14|I|15|J|K]]|9|@$H|16|I|17|1|18]]|A|$]]|$1|L|3|M|5|G|7|19|8|@$H|1A|I|1B|J|K]]|9|@]|A|$]]|$1|N|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1D|8|@$H|1E|I|1F|J|K]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

Write your own syslog implementation. :-P

This can be accomplished in two ways.

<ol>
<li>Write your own <code>LD_PRELOAD</code> hook to override the syslog functions, and make them output to <code>stderr</code> instead. I actually wrote a post about this many years ago: <a href="http://marc.info/?m=97175526803720" rel="nofollow noreferrer">http://marc.info/?m=97175526803720</a> :-P</li>
<li>Write your own syslog daemon. It's just a simple matter of grabbing datagrams out of <code>/dev/log</code>! :-P</li>
</ol>

Okay, okay, so these are both facetious answers. Have you profiled <code>syslogd</code> to see where it's choking up most?

blocks|key|826934|text|您可以将syslogd的级别(或工具)配置为异步记录，方法是在日志文件的路径前加一个减号(即:+user.*+tab+-/var/+log+/user.log)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|826935|干杯。|826936|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You may configure syslogd's level (or facility) to log asynchronously, by putting a minus before path to logfile (ie.: user.* [tab] -/var/log/user.log).

Cheers.

blocks|key|3139992|text|syslog-async()实现可能会有所帮助，但在其他时候可能会有丢失日志行/有限延迟的风险。http://thekelleys.org.uk/syslog-async/|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3139993|注意:这里的“异步”是指在应用程序中对日志事件进行排队，而不是其他答案提到的异步syslogd输出文件配置选项。|3139994|entityMap|0|LINK|mutability|MUTABLE|url|http://thekelleys.org.uk/syslog-async/^0|1C|12|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

The syslog-async() implementation may help, at the risk of lost log lines / bounded delays at other times.
<a href="http://thekelleys.org.uk/syslog-async/" rel="nofollow">http://thekelleys.org.uk/syslog-async/</a>

Note: 'asynchronous' here refers to queueing log events within your application, and not the asynchronous syslogd output file configuration option that other answers refer to.

We have an application on Linux that used the <a href="http://linux.die.net/man/3/syslog" rel="noreferrer">syslog</a> mechanism. After a week spent trying to figure out why this application was running slower than expected, we discovered that if we eliminated syslog, and just wrote directly to a log file, performance improved dramatically.

I understand why syslog is slower than direct file writes. But I was wondering: Are there ways to configure syslog to optimize its performance?

Can syslog Performance Be Improved?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我们在Linux上有一个使用机制的应用程序。在花了一周的时间试图找出这个应用程序运行速度比预期慢的原因后，我们发现，如果我们消除了syslog，只需直接写入日志文件，性能就会显著提高。我理解为什么syslog比直接文件写入慢。但我想知道:有没有办法配置syslog来优化它的性能？

问是否可以提高syslog性能？
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