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-linux@vger.kernel.org).
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-linux@vger.kernel.org
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.
79 Using comp_algorithm device attribute one can see available and
99 Compression algorithms may support specific parameters which can be
101 attribute which provides a per-algorithm params configuration.
104 In addition, certain compression algorithms support pre-trained dictionaries,
106 compression algorithm to use external pre-trained dictionary, pass full
109 #pass path to pre-trained zstd dictionary
116 #pass path to pre-trained zstd dictionary and compression level
120 Parameters are algorithm specific: not all algorithms support pre-trained
123 better the compression ratio, it even can take negatives values for some
131 The value can be either in bytes or you can use mem suffixes.
151 The value can be either in bytes or you can use mem suffixes.
180 zram provides a control interface, which enables dynamic (on-demand) device
185 can use /dev/zram<id>) or an error code.
189 cat /sys/class/zram-control/hot_add
195 echo X > /sys/class/zram-control/hot_remove
200 Per-device statistics are exported as various nodes under /sys/block/zram<id>/
203 please read Documentation/ABI/testing/sysfs-block-zram.
212 mem_limit WO specifies the maximum amount of memory ZRAM can
215 can write out to backing device as 4KB unit
243 invalid_io The number of non-page-size-aligned I/O requests
270 can be calculated using compr_data_size and this statistic.
272 mem_limit the maximum amount of memory ZRAM can use to store
321 ---------
323 With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
342 Additionally, when CONFIG_ZRAM_TRACK_ENTRY_ACTIME is enabled pages can be
351 Admin can request writeback of those idle pages at right timing via::
358 this can be accomplished with::
363 algorithms can compress) this can be accomplished with::
389 If admin wants to limit writeback as per-day 400M, they could do it
421 -------------
423 With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative
424 (secondary) compression algorithms. The basic idea is that alternative
425 compression algorithm can provide better compression ratio at a price of
427 algorithm can, for example, be more successful compressing huge pages (those
429 recompression - pages that are cold and sit in the memory can be recompressed
433 one primary and up to 3 secondary ones. Primary zram compressor is explained
434 in "3) Select compression algorithm", secondary algorithms are configured
441 #1: lzo lzo-rle lz4 lz4hc [zstd]
442 #2: lzo lzo-rle lz4 [lz4hc] zstd
470 The number of idle pages can be significant, so user-space can pass a size
480 It is also possible to limit the number of pages zram re-compression will
487 During re-compression for every page, that matches re-compression criteria,
489 order of their priorities. ZRAM stops either when re-compression was
490 successful (re-compressed object is smaller in size than the original one)
491 and matches re-compression criteria (e.g. size threshold) or when there are
492 no secondary algorithms left to try. If none of the secondary algorithms can
493 successfully re-compressed the page such a page is marked as incompressible,
494 so ZRAM will not attempt to re-compress it in the future.
496 This re-compression behaviour, when it iterates through the list of
501 This can be achieved by providing a `algo` or `priority` parameter:::
512 With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
541 recompressed page (secondary compression algorithm)
543 none (including secondary) of algorithms could compress it