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.
56 if [ $? -ne 0 ]; then
72 pre-created. Default: 1.
78 allocate multiple compression streams - one per online CPU - thus
81 become offline. There is no single-compression-stream mode anymore,
91 Using comp_algorithm device attribute one can see available and
107 list primarily to simplify device configuration and one can configure
119 The value can be either in bytes or you can use mem suffixes.
139 The value can be either in bytes or you can use mem suffixes.
168 zram provides a control interface, which enables dynamic (on-demand) device
173 can use /dev/zram<id>) or an error code.
177 cat /sys/class/zram-control/hot_add
183 echo X > /sys/class/zram-control/hot_remove
188 Per-device statistics are exported as various nodes under /sys/block/zram<id>/
191 please read Documentation/ABI/testing/sysfs-block-zram.
200 mem_limit WO specifies the maximum amount of memory ZRAM can
203 can write out to backing device as 4KB unit
232 invalid_io The number of non-page-size-aligned I/O requests
259 can be calculated using compr_data_size and this statistic.
261 mem_limit the maximum amount of memory ZRAM can use to store
310 ---------
312 With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
331 Additionally, when CONFIG_ZRAM_TRACK_ENTRY_ACTIME is enabled pages can be
340 Admin can request writeback of those idle pages at right timing via::
347 this can be accomplished with::
352 algorithms can compress) this can be accomplished with::
378 If admin wants to limit writeback as per-day 400M, they could do it
410 -------------
412 With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative
413 (secondary) compression algorithms. The basic idea is that alternative
414 compression algorithm can provide better compression ratio at a price of
416 algorithm can, for example, be more successful compressing huge pages (those
418 recompression - pages that are cold and sit in the memory can be recompressed
422 one primary and up to 3 secondary ones. Primary zram compressor is explained
423 in "3) Select compression algorithm", secondary algorithms are configured
430 #1: lzo lzo-rle lz4 lz4hc [zstd]
431 #2: lzo lzo-rle lz4 [lz4hc] zstd
459 The number of idle pages can be significant, so user-space can pass a size
471 During re-compression for every page, that matches re-compression criteria,
473 order of their priorities. ZRAM stops either when re-compression was
474 successful (re-compressed object is smaller in size than the original one)
475 and matches re-compression criteria (e.g. size threshold) or when there are
476 no secondary algorithms left to try. If none of the secondary algorithms can
477 successfully re-compressed the page such a page is marked as incompressible,
478 so ZRAM will not attempt to re-compress it in the future.
480 This re-compression behaviour, when it iterates through the list of
485 This can be achieved by providing a algo=NAME parameter:::
493 With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
522 recompressed page (secondary compression algorithm)
524 none (including secondary) of algorithms could compress it