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Ported backingswap to file to compcache-0.5 #81

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
Hi,
I wanted the backing swap to file feature in compcache-0.5 (for my old's N810 
kernel), so I backported it from 0.6.2 (seemed a task I could achieve)
I was dissapointed to discover that the backing swap device limits the size of 
the ramzswap device (after finishing the port, that happens for not reading the 
code comments first, ha!), when in fact non-compressed pages are less than 10%.
I guess the pages are sparsely written to the device, directly in it indexed 
position, instead of using a mapping. Am I right?
By the way, the backing device seems gone in zram... to make it simpler?

Consider applying it to the 0.5 package.

Original issue reported on code.google.com by maac...@gmail.com on 7 Jan 2011 at 8:49

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GoogleCodeExporter commented 9 years ago 
> I guess the pages are sparsely written to the device, directly in it indexed 
position, instead of using a mapping. Am I right?

Yes, there is direct one-to-one ident mapping between index and disk block 
number. As you guessed much better (but slightly more complicated) would be to 
reduce disk seeks, in case of disks, or spread out writes, in case of SSDs, for 
better performance. This would require maintaining another mapping in zram to 
match index locations with disk block numbers.

> By the way, the backing device seems gone in zram... to make it simpler?

Yes and there were some opposition to using the current approach for backing 
swap from folks  at LKML. So, currently I'm looking for other implement this 
feature -- essentially making xvmalloc memory swappable.

Thanks for your efforts with this patch. This seems to be much requested 
feature. I will merge this in 0.5.x branch if there are still enough users of 
that version or redirect to this issue.

Original comment by nitingupta910@gmail.com on 27 Jan 2011 at 3:44

GoogleCodeExporter commented 9 years ago 
Issue 75 has been merged into this issue.

Original comment by nitingupta910@gmail.com on 2 Oct 2012 at 10:25

GoogleCodeExporter commented 9 years ago 
I don't think I will be able to push this feature to mainline anytime soon and 
I'm no longer maintaining separate repo on this site. So, closing this issues 
for now. Thanks.

Original comment by nitingupta910@gmail.com on 2 Oct 2012 at 10:47