[Interest] memory fragmentation?

[John Weeks]

On 21-Aug-2012, at 12:52 AM, Thiago Macieira wrote:

> How? Putting up an alert usually requires allocating memory somewhere, be it 
> in your application or in the display server.

> 
> If we're already out of memory, the likelihood of another set of allocations 
> succeeding is quite low. 

If a large allocation just failed, it's actually likely that you still have a large enough block of memory left to put up an alert. That's our experience with a scientific application, at least. We don't usually fail from a billion tiny allocations, we fail on an allocation of hundreds of megabytes.

In the old days on Macintosh (our application has been shipping since 1989) you would pre-allocate a block of memory that could be released under low-memory conditions just in order to show this alert. There's nothing preventing an application from pre-making the Out of Memory alert at start-up if such conditions are likely. Which they actually aren't (see first paragraph).

> Not to mention that, by the time you do run out of 
> memory, the chances are that the system has been swapping hard for several 
> minutes. The user will have likely pressed the Reset button long ago.

That's always possible. They call tech support about that, too. Even a 32-bit application benefits from running on a 64-bit machine with lots of physical memory. On Windows, you even get an extra GByte in your address space.

-John Weeks

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