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@@ -1,5 +1,8 @@
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+.. _zsmalloc:
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+
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+========
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zsmalloc
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---------
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+========
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This allocator is designed for use with zram. Thus, the allocator is
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supposed to work well under low memory conditions. In particular, it
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@@ -31,40 +34,49 @@ be mapped using zs_map_object() to get a usable pointer and subsequently
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unmapped using zs_unmap_object().
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stat
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-----
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+====
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With CONFIG_ZSMALLOC_STAT, we could see zsmalloc internal information via
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-/sys/kernel/debug/zsmalloc/<user name>. Here is a sample of stat output:
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+``/sys/kernel/debug/zsmalloc/<user name>``. Here is a sample of stat output::
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-# cat /sys/kernel/debug/zsmalloc/zram0/classes
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+ # cat /sys/kernel/debug/zsmalloc/zram0/classes
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class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage
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- ..
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- ..
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+ ...
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+ ...
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9 176 0 1 186 129 8 4
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10 192 1 0 2880 2872 135 3
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11 208 0 1 819 795 42 2
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12 224 0 1 219 159 12 4
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- ..
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- ..
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+ ...
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+ ...
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+
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+class
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+ index
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+size
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+ object size zspage stores
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+almost_empty
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+ the number of ZS_ALMOST_EMPTY zspages(see below)
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+almost_full
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+ the number of ZS_ALMOST_FULL zspages(see below)
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+obj_allocated
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+ the number of objects allocated
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+obj_used
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+ the number of objects allocated to the user
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+pages_used
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+ the number of pages allocated for the class
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+pages_per_zspage
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+ the number of 0-order pages to make a zspage
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-class: index
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-size: object size zspage stores
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-almost_empty: the number of ZS_ALMOST_EMPTY zspages(see below)
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-almost_full: the number of ZS_ALMOST_FULL zspages(see below)
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-obj_allocated: the number of objects allocated
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-obj_used: the number of objects allocated to the user
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-pages_used: the number of pages allocated for the class
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-pages_per_zspage: the number of 0-order pages to make a zspage
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+We assign a zspage to ZS_ALMOST_EMPTY fullness group when n <= N / f, where
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-We assign a zspage to ZS_ALMOST_EMPTY fullness group when:
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- n <= N / f, where
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-n = number of allocated objects
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-N = total number of objects zspage can store
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-f = fullness_threshold_frac(ie, 4 at the moment)
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+* n = number of allocated objects
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+* N = total number of objects zspage can store
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+* f = fullness_threshold_frac(ie, 4 at the moment)
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Similarly, we assign zspage to:
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- ZS_ALMOST_FULL when n > N / f
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- ZS_EMPTY when n == 0
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- ZS_FULL when n == N
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+
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+* ZS_ALMOST_FULL when n > N / f
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+* ZS_EMPTY when n == 0
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+* ZS_FULL when n == N
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Mike Rapoport