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The book is available and called simply "Understanding The Linux Virtual Memory Manager". There is a lot of additional material in the book that is not available here, including details on later 2.4 kernels, introductions to 2.6, a whole new chapter on the shared memory filesystem, coverage of TLB management, a lot more code commentary, countless other additions and clarifications and a CD with lots of cool stuff on it. This material (although now dated and lacking in comparison to the book) will remain available although I obviously encourge you to buy the book from your favourite book store :-) . As the book is under the Bruce Perens Open Book Series, it will be available 90 days after appearing on the book shelves which means it is not available right now. When it is available, it will be downloadable from http://www.phptr.com/perens so check there for more information.
To be fully clear, this webpage is not the actual book.
Next: 11. Page Frame Reclamation Up: 10. High Memory Management Previous: 10.4 Bounce Buffers   Contents   Index
Two emergency pools of
buffer_heads and pages are maintained
for the express use by bounce buffers. If memory is too tight for allocations,
failing to complete IO requests is going to compound the situation as buffers
from high memory cannot be freed until low memory is available. This leads
to processes halting, thus preventing the possibility of them freeing up their
The pools are initialised by
init_emergency_pool() to contain
POOL_SIZE10.5 entries each. The
pages are linked via the
list field on a list headed
emergency_pages. Figure 10.5 illustrates how pages are stored on emergency pools and
acquired when necessary.
buffer_heads are very similar as they linked via the
inode_buffers on a list headed by
emergency_bhs. The number of entries left on the pages and
buffer lists are recorded by two counters
nr_emergency_bhs respectively and the two lists are protected
Next: 11. Page Frame Reclamation Up: 10. High Memory Management Previous: 10.4 Bounce Buffers   Contents   Index Mel 2004-02-15