Search the FAQ Archives

3 - A - B - C - D - E - F - G - H - I - J - K - L - M
N - O - P - Q - R - S - T - U - V - W - X - Y - Z - Internet FAQ Archives

comp.unix.aix Frequently Asked Questions (Part 2 of 5)
Section - 1.300: Some info about the memory management system

( Part1 - Part2 - Part3 - Part4 - Part5 - Single Page )
[ Usenet FAQs | Web FAQs | Documents | RFC Index | Business Photos and Profiles ]

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:

Report this comment as inappropriate
Aug 17, 2019 @ 4:04 am
The Rise Of The online dating site Industry

online dating service personals is going mainstream. This week just in time for Valentine's Day the Pew Research Center released a new study on online dating and found that 15% of American adults have used online dating sites and/or mobile dating apps, Up outside of 11% in 2013. Adults that was executed in summer 2015.

And the rapid growth in online dating is as much about money as it is love.

Young adults are leading the surge in international dating, With usage among 18 to 24 year olds almost tripling since Pew's 2013 uniform dating study. refer to it the Tinder factor: 22% of young adults get a mobile dating app, when compared just 5% just two years earlier.

But young people aren't the only ones in search of the digital get down. The study reveals that 55 to 64 year olds are also flocking to international dating, With 12% of older adults having tried it double the amount 6% reported back in 2013.

online dating sites is a big market. this assists explain why IAC/InterActiveCorp (IACI) Decided to spin off its online dating [url=]latino dating[/url] assets last year with the Match Group (nasdaq:MTCH) initial public offering.

dating foreign girls is also gaining traction overseas, such as in China, Where revenue is roughly to total $1.6 billion for the year towards the end of 2016. Investors want to the market's potential: last year, German media firm Bertelsmann spent $5 million in dating app Tantan, While Sequoia Capital and Vertex go Holdings put $20.5 million throughout to Qingchifan, an additional app.

nevertheless, Despite the ever increasing popularity of online dating, Concerns remain over the industry's ability to get a profit. the key issue is that, When the apps work and people find partners, They stop having the service. consequently, Dating apps must be adept at acquiring new customers. all the same, As the Wall Street Journal highlights, Most dating apps don't experience the same meteoric rise that Grindr and Tinder have, And users generally don't recommend the most recent apps to their friends.

Match's first quarterly earnings illustrate the possible hurdles within the online dating industry. While the company beat visions with $0.24 earnings per share when compared to the consensus estimate of $0.19, gross income came up short. Analysts had envisioned $272 million for the fourth quarter, And Match gained $267.6 million. following a earnings report, Barclays decreased the stock, And both JPMorgan and Merrill Lynch lowered their price prey.

Keeping these stretches in mind (beyond just the industry's growth), Let's evaluate what analysts expect to see from online dating companies when they next report earnings.

Analysts provide estimates many different aspects of a company's operations, Including its net income, income per share and revenue. The consensus estimate, which is the average of the provided figures, Is then used as a benchmark come earnings season. If a company outperforms estimates, That's having a positive earnings surprise and can boost a stock. instead, Missing estimates is strangling earnings surprise and can tank a stock. Just look at twittollower (nyse:TWTR).

Below is a list of international dating stocks and analyst estimates for their next quarterly earnings and revenue.

go through the interactive chart to view data over time.

1. ((nasdaq:night), gains, analysts, financials): Operates an online dating service platform in the People's Republic of China.

Average revenue approximation for Q4 2015: $28.68 million.

2. Spark cpa marketing networks Inc. ((NYSEMKT:ador), earnings, analysts, financials): Provides online personals services inside the and internationally.

Average revenue assess for Q4 2015: $12.14 million.

3. rival Group Inc. (MTCH, earnings, experts, financials): gives you dating products. current market cap at 2.35B, newest closing price (...)

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: (Jose Pina Coelho)

Last Update March 27 2014 @ 02:11 PM