Re: [PATCH 3/4] mm: zswap: add supporting for zsmalloc

[Seth Jennings <sjenning@linux.vnet.ibm.com>]

On Sun, Aug 18, 2013 at 04:40:48PM +0800, Bob Liu wrote:
> Make zswap can use zsmalloc as its allocater.
> But note that zsmalloc don't reclaim any zswap pool pages mandatory, if zswap
> pool gets full, frontswap_store will be refused unless frontswap_get happened
> and freed some space.
> 
> The reason of don't implement reclaiming zsmalloc pages from zswap pool is there
> is no requiremnet currently.
> If we want to do mandatory reclaim, we have to write those pages to real backend
> swap devices. But most of current users of zsmalloc are from embeded world,
> there is even no real backend swap device.
> This action is also the same as privous zram!
> 
> For several area, zsmalloc has unpredictable performance characteristics when
> reclaiming a single page, then CONFIG_ZBUD are suggested.

Looking at this patch on its own, it does show how simple it could be
for zswap to support zsmalloc.  So thanks!

However, I don't like all the ifdefs scattered everywhere.  I'd like to
have a ops structure (e.g. struct zswap_alloc_ops) instead and just
switch ops based on the CONFIG flag.  Or better yet, have it boot-time
selectable instead of build-time.

Seth