Playing with Swap Monitoring and Increasing Swap Space Using ZFS Volumes in Oracle Solaris 11
Various sections of the act stipulate that information regarding swap limits risk management options of participants who do not meet trading threshholds. I have one badz.info any one tell me why out put of df command does not show me swap space on my system. Please let me know whether swap is enabled or not,if it is enabled why it is not showing in df command. Swap isn't a filesystem (like e.g. ext3) and thus isn't mounted in. withColumn("hasRed", array_contains('values, "red")) // gives null for no option val colorPicker = when('hasRed, "red") val result = badz.info(redOrNot, "fn").
Another very good way to monitor the swap space is the following command: A rough comparison would be a high-watermark threshold. Remember that swap space is reserved when the virtual memory heap segment or anonymous memory for a process is created, and the reserved swap space is then allocated when the process is run. Anonymous memory is made of pages that don't have a counterpart in any file system and that are migrated to the swap space due to a shortage of physical memory RAM —probably because the sum of the stack, the shared memory, and the process heap from the malloc function, for example is larger than the amount of available memory.
Additionally, we must remember that some swap space is reserved when the virtual memory for a process is created, but only part of this reserved space is really associated with the address space of the process; otherwise, the swap -s output can be misinterpreted, because it is telling us that k is, at the end, reserved in order to allocate a space, the space must has been reserved previously and K of swap space has been touched. Another very important point is that the swap -l command reports the physical swap space on disk while swap -s reports virtual swap space, which is the sum of the physical swap space and the physical memory.
Therefore, the available swap space from swap -s is the sum of free physical swap space plus free physical memory space. That's the reason that the swap -s command is not recommended for evaluating the physical swap space; instead, swap -l should be used for this goal. If we want to try another way to get the swap information, we can use the echo:: As mentioned earlier, it's good to remember that anonymous memory doesn't have a counterpart in the file system. Usually, anonymous pages are the private data of a process, which includes the process heap anonymous data and the thread structure the stack area, for example.
Swapping—an operation in which the swapper process sched swaps out processes that have been sleeping for more than 20 seconds first their thread structures and then the stack and heap data [anonymous page] —shouldn't be confused with paging, which is moving pages normally 4 KB or 8 KB each from memory to disk and usually results in very efficient memory management.
However, one kind of paging has a horrible effect on system performance—anonymous paging mainly anonymous page-in —because it increases application latency for reading back data from a disk. How can you verify whether a system is using anonymous pages?
In the following output, the columns that are interesting are apo anonymous page-out and api anonymous page-inwhich both ideally should be equal to zero. The latter is responsible for an increase in application latency. Usually, when the amount of free memory goes below the amount specified by the desfree kernel parameter and then below the amount specified by the minfree kernel parameter, page scanning becomes more intensive. If the amount of free memory stays below the desfree value for 30 seconds or more, the system starts swapping.
The worst form of swapping is hard swapping, which is when some inactive kernel modules are unloaded and moved to the swap space. We can monitor whether the system is hard swapping by using the following command: The amount of free memory needs to be below desfree for more than 30 seconds, AND There must constantly be two pending processes on the run queue the r column in the vmstat output belowAND freemem must be below minfree OR the number of page-ins plus page-outs must be greater than maxpgio, where maxpgio is the number of page-out requests that can be queued by the paging system.
Therefore, maxpgio depends on the number of swap devices using their own disk controller. Its default value is 40 pages.
Disk Space Management with Disk Partitions An extreme method of enforcing disk use quotas is to create a disk partition and filesystem for each user account and to mount the filesystem on an empty directory as the user's home directory.
Then, when users run out of disk space, they will not be able to create or enlarge any files. When users attempt to write or create a file that takes them over their limit, they receive an error message indicating that no disk space is left on the device.
This method of disk control is not generally recommended. It requires a great deal of preparation and maintenance on the part of the administrator, and is not easily modified once in place. Additionally, fragmenting your disk into many small partitions reduces the total amount of available disk space and produces a performance overhead on your system.
In this case, the disk controller must write a user's files within only one small partition, instead of in the next convenient place on the disk. Consider this method of disk space control only if your system is so overloaded and your users so obstinate that all other measures have failed.
Wasted Disk Space Sometimes there is a great deal of wasted disk space on a system.
swap space does not show in df command
When you are low on space, check to make sure that large files have not accumulated in the temporary directories or in the administrative directories. These files can take up large amounts of space many megabytes and should be archived on tape and removed from your system. If you have system auditing enabled, be aware that this facility generates very large audit trail record files, and these need to be archived to tape on a regular perhaps daily basis.
Also, check any UUCP or ftp directories you may have available, and generally look for core files, and any other large and unnecessary files that may exist on your system. Swap Space T he IRIX operating system uses a portion of the disk as swap space for temporarily saving part or all of a user's program when there is not enough physical memory to contain all of the running programs. If you run many very large programs, you might run out of swap space.
The IRIX system allows programs occupying more space than the system limit to run, since each program is only partially loaded into memory at any given time.
One of the effects of this policy is that the IRIX system has to preallocate swap space based on likely future usage, and sometimes this prediction is incorrect. When the swap space is actually needed, the IRIX system allocates the most convenient available space, not the specific space allocated. So the physical allocation is separate from the accounting allocation.
If your system preallocates all your swap space, but the space has not yet been used, it may appear that your system is running out of swap space when it is not. It is possible that your system has simply preallocated the rights to future swap space to existing processes, and no new processes can allocate space due to the strict swap space accounting in the IRIX system. Strict swap space accounting is always in effect, but the ability to add both physical and virtual swap space through ordinary system files allows the administrator to add swap space or to effectively turn off strict swap space accounting, without having to either repartition the disk or reconfigure and reboot the system.
Monitoring Paging and Swap Space Use sar -p, sar -w, sar -q, swap -s, and swap -l to monitor paging and swap space use.
If you find that you are running out of swap space, two solutions are available: Adding swap space does not improve the performance of large programs, but it permits them to run successfully.
Your kernel should then allow more processes to execute. However, when an attempt is made to access more than the system limit, the IRIX system swaps the largest running program out of memory. The output of the swap -s command looks something like: So, at this point, the system is not swapping, but the programs running on the system have requested approximately 17 MB of swap space, just in case they need to grow.
Many applications reserve what is known as virtual swap space. That is, they request more memory than they will ever need. The actual size of the application is the amount of physical system resources that the application is using. The virtual size of the application is the amount of system resources it is using plus the amount of extra resources requested but not in use.
This is the case in the above example; space has been reserved, but is not in use. Negative Swap Space Look at another example of swap -s output: The swap -s output does not take main memory into account.
The data that is shown in the negative is actually data that is contained in system memory. It appears that approximately 20 MB of physical swap space is in use, as shown by the amount of allocated space. Therefore, the system is not out of physical swap space.
If there was no more physical swap space, the number of allocated blocks would be very close to the number of blocks reported by the swap -l command. This appears to leave an overrun of 10 MB. So, as long as that negative number has an absolute value less than approximately the amount of physical memory obtained from the hinv command that you have, you have not overrun your system.
The following example shows swap -s output of a system that has most likely come to its swapping limit: If the swap -l in this example were to report blocks of physical swap space on the system, it is easy to see that there are only physical blocks that are not in use. Turning On Virtual Swapping If swap -s reports a negative number, increase virtual swap when your system is not near its physical limits. This allows your system to allocate space to those applications that grab more space than they actually need.
To do this, you can turn on virtual swapping by entering the following commands: If virtual swapping is already on use chkconfig to find out or if the number of allocated blocks is approaching the number of blocks reported by the swap -l command, the only way to remedy the situation is to add more physical memory or swap space.
See the swap 1M man page for more information regarding adding swap space whether through another disk partition or a swap file.
Playing with Swap Monitoring and Increasing Swap Space Using ZFS Volumes
This section explains how to increase the size of the swap partition on a single disk. You can increase your available swap space by repartitioning your disk, as described earlier in this chapter, or you can add space with the swap command as discussed here.
The swap command allows you to designate a portion of any disk partition as additional swap space. You can add swap space at any time and delete the new swap space when you no longer need it. There are several options available with this command, and the command is described completely in the swap 1M man page, but the most convenient method to use is to specify a normal system file as additional swap space.
To specify a file as additional swap space, you first create an empty file of appropriate size with the mkfile 1M command. The second field in the mkfile command is the size of the file. In this case, 10m specifies a file that is 10 MB in size. You can use b, k, or m as a suffix to the size argument to indicate that the size number is in bytes, kilobytes, or megabytes, respectively. For example, the following commands all produce files of 10 MB: When you make your file, be certain that the file resides in the filesystem from which you want to take the space.
Note, however, that you can also use filesystems mounted remotely via NFS. Complete information on using remote mounted filesystems for swap space is available in the swap 1M man page.
To begin using your new file as swap space, give the following command: To check your new swap space, use the command: Increasing Swap Space on a Multidisk System Adding more swap space to a multidisk system can be done just as if you were adding space on a single-disk system.
You can always use the mkfile and swap commands to add a swap file to your system. However, if you want to add dedicated swap space in a new disk partition, follow the steps in Procedure Adding Dedicated Swap Space To double the default amount of swap space, you can use another disk drive as follows: Be sure that the swap partition does not overlap any user filesystem partitions.
Verify the size of the swap partition in blocks. Place a line of the following form in the file: