Avi, so does the write to disk actually take 12 seconds? You could  
look at
writeImageFileIO or up in writeImageFile and stick a fork there and  
have the child do the I/O.
A bit further away from the OO space at this point so it's clearer  
what you are doing perhaps.


On 7-Oct-05, at 4:34 PM, Avi Bryant wrote:

>
> On Oct 7, 2005, at 4:09 PM, John M McIntosh wrote:
>
>
>> Of course if you have a  spare GB or two, you could do the fullGC  
>> ask for a block of memory, copy start of memory to end of memory  
>> there, then write that out
>> at your leisure, that forgoes the need for fork and the like.  
>> Assumes of course you can ask and get 500MB at no cost.
>> Surely the write happens quite quickly on modern high-speed disk i/ 
>> o machines tho?
>> Seems to me if you're wanting to minimize downtime you fork and do  
>> a snapshot, that as noticed takes upwards of image size to do.
>> Otherwise as you say full GC, fork for the write, but does that   
>> save anything?
>>
>
> The scenario is that you have a server packed with large images  
> that you want saving to disk periodically.  So mostly what I'm  
> trying to optimize is memory usage, but without unreasonable delay  
> by the standards of web applications.  The two options that take  
> more or less constant memory seem to be a regular snapshot, or GC- 
> >fork->snapshot.  For a largish image (100-200MB), a GC takes maybe  
> 2s (acceptable, if annoying) whereas a snapshot takes maybe 15s  
> (pretty much unacceptable).  So the forking seems like the right  
> choice.  Though if we could get rid of the GC altogether that would  
> be great...
>
> Avi
>
>
>
>

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