Lines Matching +full:can +full:- +full:secondary
2 zram: Compressed RAM-based block devices
8 The zram module creates RAM-based block devices named /dev/zram<id>
20 There are several ways to configure and manage zram device(-s):
23 b) using zramctl utility, provided by util-linux (util-[email protected]).
28 In order to get a better idea about zramctl please consult util-linux
29 documentation, zramctl man-page or `zramctl --help`. Please be informed
30 that zram maintainers do not develop/maintain util-linux or zramctl, should
31 you have any questions please contact util-[email protected]
45 -EBUSY an attempt to modify an attribute that cannot be changed once
47 -ENOMEM zram was not able to allocate enough memory to fulfil your
49 -EINVAL invalid input has been provided.
50 -EAGAIN re-try operation later (e.g. when attempting to run recompress
58 if [ $? -ne 0 ]; then
74 pre-created. Default: 1.
80 allocate multiple compression streams - one per online CPU - thus
83 become offline. There is no single-compression-stream mode anymore,
93 Using comp_algorithm device attribute one can see available and
113 Compression algorithms may support specific parameters which can be
115 attribute which provides a per-algorithm params configuration.
118 In addition, certain compression algorithms support pre-trained dictionaries,
120 compression algorithm to use external pre-trained dictionary, pass full
123 #pass path to pre-trained zstd dictionary
130 #pass path to pre-trained zstd dictionary and compression level
134 Parameters are algorithm specific: not all algorithms support pre-trained
137 better the compression ratio, it even can take negatives values for some
145 The value can be either in bytes or you can use mem suffixes.
165 The value can be either in bytes or you can use mem suffixes.
194 zram provides a control interface, which enables dynamic (on-demand) device
199 can use /dev/zram<id>) or an error code.
203 cat /sys/class/zram-control/hot_add
209 echo X > /sys/class/zram-control/hot_remove
214 Per-device statistics are exported as various nodes under /sys/block/zram<id>/
217 please read Documentation/ABI/testing/sysfs-block-zram.
226 mem_limit WO specifies the maximum amount of memory ZRAM can
229 can write out to backing device as 4KB unit
259 invalid_io The number of non-page-size-aligned I/O requests
286 can be calculated using compr_data_size and this statistic.
288 mem_limit the maximum amount of memory ZRAM can use to store
337 ---------
339 With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
358 Additionally, when CONFIG_ZRAM_TRACK_ENTRY_ACTIME is enabled pages can be
367 Admin can request writeback of those idle pages at right timing via::
374 this can be accomplished with::
379 algorithms can compress) this can be accomplished with::
405 If admin wants to limit writeback as per-day 400M, they could do it
437 -------------
439 With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative
440 (secondary) compression algorithms. The basic idea is that alternative
441 compression algorithm can provide better compression ratio at a price of
443 algorithm can, for example, be more successful compressing huge pages (those
445 recompression - pages that are cold and sit in the memory can be recompressed
449 one primary and up to 3 secondary ones. Primary zram compressor is explained
450 in "3) Select compression algorithm", secondary algorithms are configured
457 #1: lzo lzo-rle lz4 lz4hc [zstd]
458 #2: lzo lzo-rle lz4 [lz4hc] zstd
486 The number of idle pages can be significant, so user-space can pass a size
496 It is also possible to limit the number of pages zram re-compression will
503 During re-compression for every page, that matches re-compression criteria,
505 order of their priorities. ZRAM stops either when re-compression was
506 successful (re-compressed object is smaller in size than the original one)
507 and matches re-compression criteria (e.g. size threshold) or when there are
508 no secondary algorithms left to try. If none of the secondary algorithms can
509 successfully re-compressed the page such a page is marked as incompressible,
510 so ZRAM will not attempt to re-compress it in the future.
512 This re-compression behaviour, when it iterates through the list of
517 This can be achieved by providing a `algo` or `priority` parameter:::
528 With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
557 recompressed page (secondary compression algorithm)
559 none (including secondary) of algorithms could compress it