Proc file system stat

If the mapping is not associated with a file:. So if a process has pages all to itself, and shared with one other process, its PSS will be Please note that the printed value might be lower than the real value due to optimizations used in the current implementation. If this is not desirable please file a bug report. It just shows the current status. This member represents the kernel flags associated with the particular virtual memory area in two letter encoded manner.

The codes are the following:. Note that there is no guarantee that every flag and associated mnemonic will be present in all further kernel releases. Things get changed, the flags may be vanished or the reverse — new added. Interpretation of their meaning might change in future as well. So each consumer of these flags has to follow each specific kernel version for the exact semantic.

This typically manifests when doing partial reads of these files while the memory map is being modified. Despite the races, we do provide the following guarantees:. Additionally, it contains these fields:. They represent the proportional shares of anonymous, file, and shmem pages, as described for smaps above.

These fields are omitted in smaps since each mapping identifies the type anon, file, or shmem of all pages it contains. To clear the bits for all the pages associated with the process:. For detailed explanation, see Examining Process Page Tables. The output follows a general format where mapping details get summarized separated by blank spaces, one mapping per each file line:.

Similar to the process entries, the kernel data files give information about the running kernel. Not all of these will be present in your system. It depends on the kernel configuration and the loaded modules, which files are there, and which are missing. Example: 0. The new vectors are:. Only available on some systems. This interrupt may also be generated when the temperature drops back to normal.

Hence the APIC sees the interrupt but does not know what device it came from. This might also be generated by chipset bugs. Typically, their statistics are used by kernel developers and interested users to determine the occurrence of interrupts of the given type. The above IRQ vectors are displayed only when relevant. Others are suppressed when the system is a uniprocessor.

You can set it by doing:. This hardware locality information does not include information about any possible driver locality preference. Default value is ffffffff all CPUs if there are only 32 of them. As usual the kernel has more info than you and does a better job than you, so the defaults are the best choice for almost everyone. The general rule is that the contents, or even the existence of these directories, depend on your kernel configuration.

If SCSI is not enabled, the directory scsi may not exist. The same is true with the net, which is there only when networking support is present in the running kernel. The slabinfo file gives information about memory usage at the slab level. Linux uses slab pools for memory management above page level in version 2.

Commonly used objects have their own slab pool such as network buffers, directory cache, and so on. External fragmentation is a problem under some workloads, and buddyinfo is a useful tool for helping diagnose these problems. Buddyinfo will give you a clue as to how big an area you can safely allocate, or why a previous allocation failed. Each column represents the number of pages of a certain order which are available. Fragmentation avoidance in the kernel works by grouping pages of different migrate types into the same contiguous regions of memory called page blocks.

A page block is typically the size of the default hugepage size, e. By keeping pages grouped based on their ability to move, the kernel can reclaim pages within a page block to satisfy a high-order allocation. The pagetypinfo begins with information on the size of a page block.

It then gives the same type of information as buddyinfo except broken down by migrate-type and finishes with details on how many page blocks of each type exist. Some of the Reclaimable blocks should also be allocatable although a lot of filesystem metadata may have to be reclaimed to achieve this. Provides information about distribution and utilization of memory. This varies by architecture and compile options.

Some of the counters reported here overlap. The memory reported by the non overlapping counters may not add up to the overall memory usage and the difference for some workloads can be substantial.

You may not have all of these fields. An estimate of how much memory is available for starting new applications, without swapping. The estimate takes into account that the system needs some page cache to function well, and that not all reclaimable slab will be reclaimable, due to items being in use.

The impact of those factors will vary from system to system. Memory which has been less recently used. It is more eligible to be reclaimed for other purposes.

Highmem areas are for use by userspace programs, or for the pagecache. The kernel must use tricks to access this memory, making it slower to access than lowmem. Among many other things, it is where everything from the Slab is allocated. Kernel allocations that the kernel will attempt to reclaim under memory pressure. Includes SReclaimable below , and other direct allocations with a shrinker. Always zero. If you list the directories, you will find that for each PID of a process there is dedicated directory.

You can check directories only on terminal using. Skip to content. Change Language. Related Articles. Table of Contents. Improve Article. Save Article. It isn't an exact match, but a solid understanding of the concepts presented in Lab10 will be incredibly helpful here. As you write the tests, look for ways to exercise all the code in your functions.

I will be running my own set of unit tests against your projects as part of the grading process so it would be a good idea to test the functions to ensure they handle expected and unexpected conditions as specified in the comments provided in ProcEntry.

When testing, be certain to check the test cases with valgrind. The provided makefile includes a memtest-mytests rule to assist with this testing. Begin the implementation of myps itself by writing the code to process the following command line options:. Stub out the -p, -c and -z options as they will be implemented in part 3. Once the command line options have been processed, build a filtered array of dirent structs that contains only PID directories.

A filter for PID directories will need to check if the dirent type is a directory and if the first character of the name is a number. For debugging purposes, go ahead and write the directory entries to the console to confirm the correct set of directories is being processed. HINT: Lab11 will be a great reference for this part of the project as well as the manpage for readdir. This can be performed manually. Once again, be sure to run these tests with valgrind to ensure no memory leaks creep into the codebase.

For basic testing, use the memtest-myps rule in the provided makefile. The number of items is determined by the number of dirents found in part 2. The following comparison function can be used to sort ProcEntry items by process id. The myps tool should sort by pid if the -p option is specified or if no sorting option is specified on the command line. You will need to implement a second comparison function to enable sorting by command comm as specified by the -c command line option.

This is also where myps will implement the -z option to display only ProcEntry items that are in the zombie Z state. Use the following code, verbatim, to display column headers that align with the output of the PrintProcEntry function provided above:. HINT: Lab12, particularly mysort, will be an excellent reference for this part of the project. There are points allocated to this project, the equivilant of five labs.