Optimizing the performance of IIS application pool requires balancing resources and stability. Key points include: 1. Setting the appropriate recycling time, it is recommended to recover at low peaks every day or trigger it according to memory; 2. Control the memory upper limit (such as 512MB~1GB) to prevent resource scrambling; 3. Enable fast fault isolation, adjust the error threshold to avoid misblocking; 4. Adjust the idle timeout time, and improve response speed in combination with preloading.

The performance setting optimization of IIS application pool is actually to find a balance point between resource allocation and stability. You may have noticed that if the configuration is not reasonable, the website response will slow down and even timeout or crash. Especially when the number of visits is large, unreasonable configuration will cause you to frequently check problems and are very inefficient.

The following key settings are something that most users are prone to ignore but are very important:

1. Set the appropriate recycling time (Regular Time Interval)

By default, IIS will automatically recycle the application pool every 1740 minutes (that is, 29 hours). Although this setting is safe, it is not suitable for many applications with high concurrency or memory sensitive.

• If your application has more caches or long-running tasks, too frequent recycling can cause performance jitter.
• On the contrary, if you find that memory usage continues to rise and occasionally GC pressure occurs, appropriately shortening the recovery interval can free up resources.

suggestion:

• For medium-load sites, it can be set to automatically recover once every morning during the low peak period (such as 1440 minutes).
• Or simply turn off regular recycling and use other trigger conditions (such as memory limit) to control it.

2. Control the upper limit of memory usage (Private Memory Limit)

This is a key setting to prevent an application pool from consuming too much memory affecting the entire server.

• The default value is unlimited, which is very dangerous on servers where multiple sites coexist.
• When an application pool exceeds the set private memory limit, IIS will automatically recycle it to avoid dragging down other services.

suggestion:

• The memory cap is reasonably allocated according to the expected load of each site. For example, a normal CMS site can be set to 512MB to 1GB.
• If you observe frequent recycling and memory usage is close to the upper limit, you need to consider whether the program has memory leaks or needs to add limits.

3. Enable Rapid-Fail Protection

This function is used to prevent the application pool from falling into a dead loop due to frequent crashes.

• The default setting is to disable the app pool 5 times every 5 minutes.
• This mechanism can effectively protect the overall stability of the system, but sometimes it can accidentally injure those short-term abnormal services.

suggestion:

• The enabled state is retained, but the error number and time window can be adjusted according to the actual situation. For example, change to "10 times every 5 minutes" to accommodate occasional abnormalities.
• Used with log monitoring, when fault isolation is triggered, you can promptly notify you to check the code or rely on the service.

4. Adjust the idle timeout time (Idle Time-out)

By default, the app pool will be paused after 20 minutes of idleness. This may cause significant delays in first requests for sites accessed at low frequency.

• For example, the internal system of the enterprise is only visited several times a day and has to be reloaded every time, which has a very poor user experience.
• In turn, if your server resources are tight, keeping the default or shorter time helps save resources.

suggestion:

• If you need to "on in seconds", you can adjust the idle time to longer or even set to 0 (never time out), but remember to combine it with other recycling mechanisms.
• Or use it in conjunction with "LoadUserProfile = true) preload" to achieve faster response.

Basically these key points. Optimizing the performance settings of IIS application pools is not a one-time thing, and it needs to be continuously adjusted according to actual operation. In particular, memory limits and recycling strategies directly affect stability and resource utilization, and it is worth spending time to make detailed adjustments.

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