Re: What determines VSIZE allocation?
Re: What determines VSIZE allocation?
- Subject: Re: What determines VSIZE allocation?
- From: "Michael Ash" <email@hidden>
- Date: Thu, 15 Jan 2009 11:55:22 -0500
On Thu, Jan 15, 2009 at 1:59 AM, Bill Bumgarner <email@hidden> wrote:
> On Jan 14, 2009, at 9:40 PM, Michael Ash wrote:
>>
>> On Wed, Jan 14, 2009 at 5:31 PM, Tobias Zimmerman <email@hidden>
>> wrote:
>>>
>>> I know there are people who will say "VSIZE doesn't matter if there is no
>>> paging",
>>
>> This is kind of like that famous question, "Have you stopped beating
>> your wife?" VSIZE doesn't matter, period. Paging doesn't enter into
>> it.
>>
>>> but if I ever sought to distribute my app people will not want to
>>> install a statusitem that looks like a memory hog.
>>
>> The solution there is to educate the foolish people who think that
>> VSIZE is any indication of being a "memory hog", not to artificially
>> reduce a number that has no bearing on any kind of system resource
>> usage.
>
> Generally true (though I might choose a slightly different descriptor of the
> uselessness), but not always.
>
> VSIZE *can* be a very useful indication that an application is consuming
> address space. This is not the same as consuming memory and, to the user,
> is an utterly useless distinction to make.
>
> For example, an application's VSIZE might be growing over time because it is
> mmap()'ing a bunch of files (or a few small files). If the app fails to
> unmap, the VSIZE will grow and the app may likely exhaust its address space
> without any paging activity.
>
> Example: for applications that are processing large files -- ID3 tag editors
> come to mind -- watching the VSIZE can be a useful way of determining if
> your code is properly managing the mapping of said files.
All good points. However what I meant by "system resources" was that
VSIZE, while it may indicate misbehavior in your process, never
indicates misbehavior that could affect the system as a whole. An app
with a runaway RSIZE can quickly run you into swap hell. An app with
runaway CPU usage can make everything else slow. But VSIZE is at most
an internal problem. That's all I meant to indicate.
Mike
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