Feature Request - Load Throttling

[Marc Perkel]

jw schultz wrote:

>On Tue, Feb 17, 2004 at 06:47:19PM -0800, Marc Perkel wrote:
>  
>
>>Actually - the problem is disk IO. And the disk IO is what makes the 
>>load levels go up. The load level is something that's readable can can 
>>be used to have rsync slow itself down. Nice doesn't do the trick. Nice 
>>helps - but even at nice +19 it still slows the system to a crawl when 
>>backing up from one drive to another.
>>    
>>
>
>Is that is on AIX with 12 AS400 CPUs or the VMS SSI cluster?
>Or is that a single CPU linux box with a 2.4.?? kernel?
>  
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It's on a dual xeon with 4 gigs of ram and a pair of 250 gig serial ata 
drives.

>  
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>>So - if rsync could watch the load levels and pause every now and then 
>>to put a little space between disk access at high load levels it would 
>>make it a lot friendlier to the system. The reason nice doesn't work is 
>>that once the system call is made to access the disk - nice doesn't apply.
>>    
>>
>
>What load levels?  Do you have some nice C code that can do
>that for ALL the platforms without misreading?
>
>This is what process and i/o schedulers are for.
>Maybe you should contact the people responsible for whatever
>kernel it is you are running.
>
>  
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What happens is that the server is cooking along just fine serving about 
2 million hits a day. Load level - according to top is running around 
0.6 to 2.3 or so - and then rsync kicks in doing a backup between the 
drives and even though I'm running at nice +19 the load kicks up to 
around 50 and several services almost stop. That's why I'm asking for 
this feature.

I'd rather get a response from real develpers than nay sayers telling me 
things that don't work. Its a real issue and it requires changes in 
rsync to make it work correctly.