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

Hi,

On Wed, Jun 07, 2000 at 12:23:36PM +0200, Christoph Rohland wrote:

Rik van Riel [off-list ref] writes:

quoted

Awaiting your promised integration of SHM with the shrink_mmap
queue...

Sorry Rik, there was a misunderstanding here. I would really like to
have this integration. But AFAICS this is a major task. shrink_mmap
relies on the pages to be in the page cache and the pagecache does not
handle shared anonymous pages.

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.

Cheers,
 Stephen
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