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Top Document: comp.unix.aix Frequently Asked Questions (Part 2 of 5) Previous Document: 1.212: How do I speed up backups to DLT tapes? Next Document: 1.301: How much should I trust the ps memory reports? See reader questions & answers on this topic! - Help others by sharing your knowledge 1. Does AIX use more paging space than other unix systems? Under many scenarios, AIX requires more paging space than other unix systems. The AIX VMM implements a technique called "early allocation of paging space". When a page is allocated in RAM, and it is not a "client" (NFS) or a "persistent" (disk file) storage page, then it is considered a "working" storage page. Working storage pages are commonly an application's stack, data, and any shared memory segments. So, when a program's stack or data area is increased, and RAM is accessed, the VMM will allocate space in RAM and space on the paging device. This means that even before RAM is exhausted, paging space is used. This does not happen on many other unix systems, although they do keep track of total VM used. Example 1: Workstation with 64mb RAM is running only one small application that accesses a few small files. Everything fits into RAM, including all accessed data. On AIX, some paging space will already be used. On other unix systems, paging space will be 100% free. Clearly, this is an example that shows where we use more paging space than the other machines. Example 2: Same machine as above, except we are in an environment where many applications are running with inadequate RAM. Also, the system is running applications that are started, run, left idle, and not in constant use. A session of FRAME running in a window, for example. What happens is that eventually (theoretically) all applications will be paged out at least once. On the AIX system and the other systems the total paging requirements will be the same (assuming similar malloc algorithm). The major difference is that the AIX system allocated the paging space pages before they were actually needed, and the other systems did not allocate them until they were needed. However, most other systems have an internal variable that gets incremented as virtual memory pages are used. AIX does not do this. This can cause the AIX system to run out of paging space (virtual memory), even though malloc() continues to return memory. This "feature" allows sparse memory segments to work, but requires that all normal users of malloc() (sbrk()) know how much virtual memory will be available (actually impossible), and to handle a paging space low condition. A big problem. There are some pretty obvious pros and cons to both methods of doing Virtual Memory. 2. How much paging space do I need? Concerning the rule of thumb of having 2 times RAM for paging space: this is rather simplistic, as are most rules of thumb. If the machine is in a "persistent storage environment", meaning that they have a few small programs, and lots of data, they may not need even as much as 1 times RAM for paging space. For example, a 1GB database server running on a 6000 with 256MB of RAM, and only running about 50MB of "working" storage does not need 512MB of paging space, or even 256MB. They only need the amount of paging space that will allow all their working storage to be paged out to disk. This is because the 1GB database is mostly "persistent storage", and will require little or no paging space. Excessive paging space may simply mean wasted disk space. However, avoid insufficient paging space. Tip: Don't have more than one paging space per disk. Tip: Put lots of RAM in your system - it will use it. 3. Why does vmstat show no free RAM pages? AIX uses RAM as a possibly huge disk buffer. If you read a file in the morning, that file is read into RAM, and left there. If no other programs need that RAM, that file will be left in RAM until the machine is halted. This means that if you need the file again, access will be quick. If you need that RAM, the system will simply use the pages the file were using. The pages were flushed back to disk earlier. This means that you can get a huge speedup in disk access if you have enough RAM. For example, a 200MB database will just ease into RAM if you have a 256MB system. 4. Since vmstat shows no free RAM pages, am I out of RAM? Probably not. Since disk files will be "mapped" into RAM, if vmstat shows lots of RAM pages FREE, then you probably have too much RAM (not usual on a RISC System/6000)! 5. Shouldn't the "avm" and the "fre" fields from vmstat add up to something? No. The "avm" field tells you how much "Active Virtual Memory" AIX thinks you are using. This will closely match the amount of paging space you are using. This number has *ABSOLUTELY* nothing to do with the amount of RAM you are using, and does *NOT* include your mapped files (disk files). The amount of RAM can be determined with /usr/sbin/bootinfo -r 6. Why does the "fre" field from vmstat sometimes show lots of free RAM pages? This will happen after an application that used a lot of RAM via "working" storage (not NFS storage, and not disk file or "persistent" storage) exits. When RAM pages that were used by working storage (a program's stack and data area) are no longer needed, there is no need to leave them around. AIX completely frees these RAM pages. The time to access these pages versus a RAM page holding a "sync'd" mapped file is almost identical. Therefore, there is no need to periodically "flush" RAM. 7. Is the vmstat "fre" field useful? The vmstat "fre" field represents the number of free page frames. If the number is consistently small (less than 500 pages), this is normal. If the number is consistently large (greater than 4000 pages), then you have more memory than you need in this machine. User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: comp.unix.aix Frequently Asked Questions (Part 2 of 5) Previous Document: 1.212: How do I speed up backups to DLT tapes? Next Document: 1.301: How much should I trust the ps memory reports? Part1 - Part2 - Part3 - Part4 - Part5 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: bofh@mail.teleweb.pt (Jose Pina Coelho)
Last Update March 27 2014 @ 02:11 PM
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This sunday, quite possibly 28, 2019 snapshot, Provided by the city service group, jointly for Jarniyah, contains been authenticated based on its contents and other AP reporting, Shows Syrians lifetime extinguish a fire in a field of crops, wearing Jaabar, Raqqa state, Syria. Thousands of acres of wheat and barley fields in both Syria and Iraq have been scorched by the fires within harvest season, that typically runs until mid June. "The life that we live here is already bitter, " stated Hussain Attiya, A farmer from Topzawa Kakayi in upper Iraq. "If the outcome continues like this, I would say that no one will continue to be here. I plant 500 to 600 acres on a yearly basis. still, I won't be able to do that because I can't stay here and guard the land day and night. "ISIS militants have a history of working with a "Scorched earth insurance coverage " In areas from that they can retreat or where they are defeated. Ahmed al Hashloum thoughts Inmaa, Arabic for benefits, A local civil group that supports farming. all it takes is a cigarette butt to set haystacks on fire, He brought up. Said the fires are threatening to disrupt normal food production cycles and potentially reduce food to protect months to come. The crop burning remains localized and can't be compared to pre war devastation, Beals considered that. "suffice to say, It is only the beginning of the summer and if the fires continue it could lead to a crisis, " Beals recounted,AlternativeHeadline,prepared crop burning blamed on ISIS remnants compounds misery in war torn Iraq and Syria"}
But good news is short lived in this part of the world, Where residents of the two countries struggle to face seemingly never ending violence and turmoil amid Syria's civil war and attacks by remnants of the Islamic State of Iraq and Syria (ISIS) social groups. of course, Even in locations where conflict has subsided, Fires currently raging in farmers' fields, depriving them of valuable crops.
The blazes have been blamed also consider on defeated ISIS militants seeking to avenge their losses, Or on Syrian regime forces battling to rout other armed groups. Thousands of acres of wheat and barley fields in both Syria and Iraq have been scorched by the fires within harvest season, what kind runs until mid June.
ISIS militants have a history of implementing a "Scorched earth guideline" In areas from which retreat or where they are defeated. this "A means of inflicting a collective punishment on those put aside, said Emma Beals, a completely independent Syria researcher.
ISIS militants claimed obligations for burning crops in their weekly newsletter, al Nabaa, Saying they targeted farms owned by senior officials in six Iraqi provinces and in Kurdish administered eastern Syria, sending the persistent threat from the group even after its territorial defeat.
ISIS said it burned the farms of "The apostates in Iraq together with the Levant" And required more.
"It seems that it'll be a hot summer that will burn the pockets of the apostates as well as their hearts as they burned the Muslims and their homes in the past years, this great article said.
countless acres of wheat fields around Kirkuk in northern Iraq were set on fire. Several wheat fields in the Daquq district in southern Kirkuk burned for three days straight yesterday.
In eastern Syria's Raqqa state, Farmers battled raging fires with items of cloth, bags and water trucks. Piles of hay burned and black smoke billowed above the job areas.
The Syrian Observatory for Human Rights said through 74,000 acres (30,000 hectares) linked farmland in Hassakeh, Raqqa and completely to Aleppo province to the west, Were scorched.
Activist Omar Abou Layla said local Kurdish led forces failed to react to the fires in the province of Deir el Zour, Where ISIS was uprooted from its last property in March, (...)