Re: [PATCH] VM kswapd autotuning vs. -ac7

Hi Steven,

"Stephen C. Tweedie" [off-list ref] writes:

The swap cache --- which does handle anonymous pages --- is IN the
page cache.  

The main reason SHM needs its own swap code is that normal anonymous
pages are referred to only from ptes --- the ptes either point to
the physical page containing the page, or to the swap entry.  We
cannot use that for SHM, because SysV SHM segments must be persistent
even if there are no attachers, and hence no ptes to maintain the 
location of the pages.  

If it wasn't for persistent SHM segments, it would be trivial to
integrate SHM into the normal swapper.

But for persistence we now have the shm dentries (We will have at
least. I am planning to reuse the ramfs directory handling for shm
fs. This locks the dentries into the cache for persistence). 

Couldn't we use this to get the desired behaviour? 

Just guessing
		Christoph
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