The Processes table offers a granular view of memory usage, but the Physical Memory table presents a global view. Its main feature is a bar graph that offers a unique look at memory usage Figure C. Each section of the bar graph represents a list of pages of memory. As you use your system, the memory manager works in the background moving memory back and forth between these lists. This enables it to maintain the balance between using physical memory and the hard disk, allowing your system to work most efficiently.
The Hardware Reserved list shows the amount of memory reserved for hardware. It represents the amount of memory your hardware devices have reserved so that they can communicate with the operating system. Memory reserved for hardware is essentially locked so it's unavailable to the memory manager.
As a general rule, the amount of Hardware Reserved memory ranges from 10 to 70 MB--but it can vary depending on your hardware configuration.
In some cases, it might be several hundred MB. Here are some examples of components that can affect the amount of memory reserved:.
Note: Some users have reported huge amounts of memory being allocated to the Hardware Reserved list. I haven't run into this myself so I can't verify the suggested solution, but a number of people have said that upgrading the system BIOS firmware solved the problem. The In Use list appears in green. It indicates the amount of memory being used by the operating system, drivers, and the running processes.
This memory is calculated by adding the sizes of the Modified, Standby, and Free values and subtracting the sum from the amount of recognized memory. It's listed as Total in the section just below the graph.
Shown in orange, the Modified list represents the pages of memory that contain data that has been modified but not accessed recently.
It's not technically in use, but it can be pulled into service quickly if needed. If memory in the Modified list has not been accessed in a long time, the memory manager will write the page to disk and move it to the Standby list. The Standby list is shown in blue. If contains pages that have been removed from process working sets, but that are still linked to their working sets.
The Standby list is basically a cache, but memory pages in the list are prioritized in a range of with 7 being the highest. A page related to a high priority process will receive a high priority level in the Standby list. For example, processes that are Sharable will be a high priority and pages associated with them will have the highest priority in the Standby list.
If a process needs a page that is associated with the process, and that page is now in the Standby list, the memory manager will return the page to that process' working set. However, all pages on the Standby list are available for memory allocation requests from any process. When a process requests more memory and there's not enough in the Free list, the memory manager checks the page's priority. It will then take a page with a low priority from the Standby list, initialize it, and allocate it to that process.
The Free list appears in light blue. Active 7 years, 8 months ago. Viewed 30k times. Improve this question. Mike B Mike B Can't you set the JVM max memory parameters to below whatever threshold would be "excessive" for the system?
Mat Yup. But I'm looking for a way to be alerted if the memory usage is approaching the JVM max memory value I set. What would be your reaction if you received such an alert, how would it be actionable? Just curious, sorry for the noise. Mat Exactly. It would be an additional preventative safety measure to alert me if a JVM is using more memory than I would normally expect it to but still under the JVM maximum value I set.
Add a comment. Active Oldest Votes. The Win OS can send alerts for performance counter threshold conditions. Part 1 Perfmon Launch Performance Monitor perfmon. Change username if necessary. Create a new email action under the Action tab Enter all the info for from, to, subject, etc. Enter the SMTP server. You will be prompt for the password to run the task when you are not logged on.
Improve this answer. Clayton Clayton 4, 15 15 silver badges 24 24 bronze badges. When the Resource Monitor window opens, click the Memory tab. In the upper section here you will see a list of running processes and how much memory they are using. In the navigation pane, expand Monitoring Tools, and then choose Performance Monitor. In the console pane toolbar, choose the View Log Data button. In the Data Source section, select Log files, and then choose the Add button. Performance monitor Performance counters are bits of code that monitor, count, or measure events in software , which allow us to see patterns from a high-level view.
Setting the right minimum memory, maximum memory, garbage collectors, and Heap Ratios varies from application to application. The right parameters can be set by performing load tests and a lot of trial and error. And you'll want to analyze your logs to make sure everything's going as planned.
Used when Parallel Garbage collectors are configured. Refer to the section [Non-Standard Options] of this link for more details on the above VM parameters. Refer to this link for more info on GC tuning.
This can be achieved by adding the following VM parameters. This will enable the. I am not recommending any specific methodology to monitor your java application and apply appropriate fixes as the behavior of the system varies from application to application.
I have collated most of the available options for monitoring purposes. One should note that every tool and monitoring method comes with the cost, whether it's application performance or financial, if you have to license it. Thanks for visiting DZone today,. Edit Profile. Sign Out View Profile. Over 2 million developers have joined DZone. This comprehensive look at Java monitoring tools and commands will make sure you get the data you need to make your apps a success while protecting your prod environment.
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