Documentation/mm/zsmalloc.rst

6 supposed to work well under low memory conditions. In particular, it
9 (0-order) pages, it would suffer from very high fragmentation --
13 To overcome these issues, zsmalloc allocates a bunch of 0-order pages
15 pages act as a single higher-order page i.e. an object can span 0-order
20 since this satisfies the requirements of all its current users (in the
21 worst case, page is incompressible and is thus stored "as-is" i.e. in
29 issues on 32-bit systems where the VA region for kernel space mappings
59 	the number of zspages with usage ratio between 10% and 20%
61 	the number of zspages with usage ratio between 20% and 30%
63 	the number of zspages with usage ratio between 30% and 40%
65 	the number of zspages with usage ratio between 40% and 50%
67 	the number of zspages with usage ratio between 50% and 60%
69 	the number of zspages with usage ratio between 60% and 70%
71 	the number of zspages with usage ratio between 70% and 80%
73 	the number of zspages with usage ratio between 80% and 90%
75 	the number of zspages with usage ratio between 90% and 99%
85 	the number of 0-order pages to make a zspage
90 objects stored in the zspage.  The inuse counter determines the zspage's
99 Each zspage can contain up to ZSMALLOC_CHAIN_SIZE physical (0-order) pages.
104 characteristics in terms of the number of pages per zspage and the number
116 Size classes #95-99 are merged with size class #100. This means that when we
119 1632 bytes, so each object of size 1568 bytes wastes 1632-1568=64 bytes.
138 objects of size 1568 in a single zspage, using a total of 5 physical pages.
143 such as pages per-zspage and objects per-zspage also change. This leads to
144 dewer class mergers, resulting in a more compact grouping of classes, which
158 to size class #254, which stores each object in its own physical page (objects
159 in huge classes do not share pages).
161 Increasing the size of the chain of zspages also results in a higher watermark
224 ----------------
255 Using larger zspage chains may result in using fewer physical pages, as seen
256 in the example where the number of physical pages used decreased from 159955
261 memory pressure (as some zspages have larger chain sizes) in cases where there
263 objects and release zspages. In these cases, it is recommended to decrease
270 .. kernel-doc:: mm/zsmalloc.c