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 zram has built-in support for idle pages tracking (that is, allocated but
331 Additionally, when CONFIG_ZRAM_TRACK_ENTRY_ACTIME is enabled, pages can be
341 ---------
343 With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
354 Admin can request writeback of idle pages at right timing via::
361 this can be accomplished with::
366 algorithms can compress) this can be accomplished with::
378 `LOW-HIGH` range (or ranges) of pages to be written-back. This reduces the
379 number of syscalls, but more importantly this enables optimal post-processing
383 echo "page_indexes=1-100 page_indexes=200-300" > \
389 echo page_index=42 page_index=99 page_indexes=100-200 \
390 page_indexes=500-700 > /sys/block/zramX/writeback
409 If admin wants to limit writeback as per-day 400M, they could do it
441 -------------
443 With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative
444 (secondary) compression algorithms. The basic idea is that alternative
445 compression algorithm can provide better compression ratio at a price of
447 algorithm can, for example, be more successful compressing huge pages (those
449 recompression - pages that are cold and sit in the memory can be recompressed
453 one primary and up to 3 secondary ones. Primary zram compressor is explained
454 in "3) Select compression algorithm", secondary algorithms are configured
461 #1: lzo lzo-rle lz4 lz4hc [zstd]
462 #2: lzo lzo-rle lz4 [lz4hc] zstd
490 The number of idle pages can be significant, so user-space can pass a size
500 It is also possible to limit the number of pages zram re-compression will
505 During re-compression for every page, that matches re-compression criteria,
507 order of their priorities. ZRAM stops either when re-compression was
508 successful (re-compressed object is smaller in size than the original one)
509 and matches re-compression criteria (e.g. size threshold) or when there are
510 no secondary algorithms left to try. If none of the secondary algorithms can
511 successfully re-compressed the page such a page is marked as incompressible,
512 so ZRAM will not attempt to re-compress it in the future.
514 This re-compression behaviour, when it iterates through the list of
519 This can be achieved by providing a `algo` or `priority` parameter:::
530 With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
559 recompressed page (secondary compression algorithm)
561 none (including secondary) of algorithms could compress it