kernel.git/drivers/block/zram/Kconfig, branch linux-6.6.y

zram: split memory-tracking and ac-time tracking

2024-12-14T18:59:44Z

[ Upstream commit a7a0350583ba51d8cde6180bb51d704b89a3b29e ] ZRAM_MEMORY_TRACKING enables two features: - per-entry ac-time tracking - debugfs interface The latter one is the reason why memory-tracking depends on DEBUG_FS, while the former one is used far beyond debugging these days. Namely ac-time is used for fine grained writeback of idle entries (pages). Move ac-time tracking under its own config option so that it can be enabled (along with writeback) on systems without DEBUG_FS. [senozhatsky@chromium.org: ifdef fixup, per Dmytro] Link: https://lkml.kernel.org/r/20231117013543.540280-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20231115024223.4133148-1-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Dmytro Maluka Signed-off-by: Andrew Morton Stable-dep-of: d37da422edb0 ("zram: clear IDLE flag in mark_idle()") Signed-off-by: Sasha Levin

zram: introduce recompress sysfs knob

2022-11-30T23:58:51Z

Allow zram to recompress (using secondary compression streams) pages. Re-compression algorithms (we support up to 3 at this stage) are selected via recomp_algorithm: echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm Please read documentation for more details. We support several recompression modes: 1) IDLE pages recompression is activated by `idle` mode echo "type=idle" > /sys/block/zram0/recompress 2) Since there may be many idle pages user-space may pass a size threshold value (in bytes) and we will recompress pages only of equal or greater size: echo "threshold=888" > /sys/block/zram0/recompress 3) HUGE pages recompression is activated by `huge` mode echo "type=huge" > /sys/block/zram0/recompress 4) HUGE_IDLE pages recompression is activated by `huge_idle` mode echo "type=huge_idle" > /sys/block/zram0/recompress [senozhatsky@chromium.org: we should always zero out err variable in recompress loop[ Link: https://lkml.kernel.org/r/20221110143423.3250790-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20221109115047.2921851-5-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Acked-by: Minchan Kim Cc: Nathan Chancellor Cc: Alexey Romanov Cc: Nhat Pham Cc: Nitin Gupta Cc: Suleiman Souhlal Signed-off-by: Andrew Morton

zram: fix Kconfig dependency warning

2022-05-25T17:47:47Z

ZSMALLOC depends on MMU so ZRAM should also depend on MMU since 'select' does not follow any dependency chains. Fixes this Kconfig warning: WARNING: unmet direct dependencies detected for ZSMALLOC Depends on [n]: MMU [=n] Selected by [y]: - ZRAM [=y] && BLK_DEV [=y] && BLOCK [=y] && SYSFS [=y] && (CRYPTO_LZO [=y] || CRYPTO_ZSTD [=m] || CRYPTO_LZ4 [=m] || CRYPTO_LZ4HC [=n] || CRYPTO_842 [=n]) Link: https://lkml.kernel.org/r/20220522204027.22964-1-rdunlap@infradead.org Fixes: b3fbd58fcbb10 ("mm: Kconfig: simplify zswap configuration") Signed-off-by: Randy Dunlap Acked-by: Johannes Weiner Cc: Minchan Kim Cc: Nitin Gupta Cc: Sergey Senozhatsky Cc: Jens Axboe Signed-off-by: Andrew Morton

mm: Kconfig: simplify zswap configuration

2022-05-19T21:08:53Z

- CONFIG_ZRAM: Zram is a user-facing feature, whereas zsmalloc is not. Don't make the user chase down a technical dependency like that, just select it in automatically when zram is requested. The CONFIG_CRYPTO dependency is redundant due to more specific deps. - CONFIG_ZPOOL: This is not a user-facing feature. Hide the symbol and have it selected in as needed. - CONFIG_ZSWAP: Select CRYPTO instead of depend. Common pattern. - Make the ZSWAP suboptions and their descriptions (compression, allocation backend) a bit more straight-forward for the user. Link: https://lkml.kernel.org/r/20220510152847.230957-5-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Cc: Dan Streetman Cc: Michal Hocko Cc: Minchan Kim Cc: Roman Gushchin Cc: Seth Jennings Cc: Shakeel Butt Signed-off-by: Andrew Morton

zram: break the strict dependency from lzo

2020-12-15T20:13:47Z

From the beginning, the zram block device always enabled CRYPTO_LZO, since lzo-rle is hardcoded as the fallback compression algorithm. As a consequence, on systems where another compression algorithm is chosen (e.g. CRYPTO_ZSTD), the lzo kernel module becomes unused, while still having to be built/loaded. This patch removes the hardcoded lzo-rle dependency and allows the user to select the default compression algorithm for zram at build time. The previous behaviour is kept, as the default algorithm is still lzo-rle. Link: https://lkml.kernel.org/r/20201207121245.50529-1-rsalvaterra@gmail.com Signed-off-by: Rui Salvaterra Suggested-by: Sergey Senozhatsky Suggested-by: Minchan Kim Acked-by: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

docs: blockdev: add it to the admin-guide

2019-07-15T14:03:01Z

The blockdev book basically contains user-faced documentation. Signed-off-by: Mauro Carvalho Chehab

docs: blockdev: convert to ReST

2019-07-15T12:20:26Z

Rename the blockdev documentation files to ReST, add an index for them and adjust in order to produce a nice html output via the Sphinx build system. The drbd sub-directory contains some graphs and data flows. Add those too to the documentation. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab

zram: support idle/huge page writeback

2018-12-28T20:11:49Z

Add a new feature "zram idle/huge page writeback". In the zram-swap use case, zram usually has many idle/huge swap pages. It's pointless to keep them in memory (ie, zram). To solve this problem, this feature introduces idle/huge page writeback to the backing device so the goal is to save more memory space on embedded systems. Normal sequence to use idle/huge page writeback feature is as follows, while (1) { # mark allocated zram slot to idle echo all > /sys/block/zram0/idle # leave system working for several hours # Unless there is no access for some blocks on zram, # they are still IDLE marked pages. echo "idle" > /sys/block/zram0/writeback or/and echo "huge" > /sys/block/zram0/writeback # write the IDLE or/and huge marked slot into backing device # and free the memory. } Per the discussion at https://lore.kernel.org/lkml/20181122065926.GG3441@jagdpanzerIV/T/#u, This patch removes direct incommpressibe page writeback feature (d2afd25114f4 ("zram: write incompressible pages to backing device")). Below concerns from Sergey: == &< == "IDLE writeback" is superior to "incompressible writeback". "incompressible writeback" is completely unpredictable and uncontrollable; it depens on data patterns and compression algorithms. While "IDLE writeback" is predictable. I even suspect, that, *ideally*, we can remove "incompressible writeback". "IDLE pages" is a super set which also includes "incompressible" pages. So, technically, we still can do "incompressible writeback" from "IDLE writeback" path; but a much more reasonable one, based on a page idling period. I understand that you want to keep "direct incompressible writeback" around. ZRAM is especially popular on devices which do suffer from flash wearout, so I can see "incompressible writeback" path becoming a dead code, long term. == &< == Below concerns from Minchan: == &< == My concern is if we enable CONFIG_ZRAM_WRITEBACK in this implementation, both hugepage/idlepage writeck will turn on. However someuser want to enable only idlepage writeback so we need to introduce turn on/off knob for hugepage or new CONFIG_ZRAM_IDLEPAGE_WRITEBACK for those usecase. I don't want to make it complicated *if possible*. Long term, I imagine we need to make VM aware of new swap hierarchy a little bit different with as-is. For example, first high priority swap can return -EIO or -ENOCOMP, swap try to fallback to next lower priority swap device. With that, hugepage writeback will work tranparently. So we could regard it as regression because incompressible pages doesn't go to backing storage automatically. Instead, user should do it via "echo huge" > /sys/block/zram/writeback" manually. == &< == Link: http://lkml.kernel.org/r/20181127055429.251614-6-minchan@kernel.org Signed-off-by: Minchan Kim Reviewed-by: Joey Pabalinas Reviewed-by: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

drivers/block: remove redundant 'default n' from Kconfig-s

2018-10-10T20:11:08Z

'default n' is the default value for any bool or tristate Kconfig setting so there is no need to write it explicitly. Also since commit f467c5640c29 ("kconfig: only write '# CONFIG_FOO is not set' for visible symbols") the Kconfig behavior is the same regardless of 'default n' being present or not: ... One side effect of (and the main motivation for) this change is making the following two definitions behave exactly the same: config FOO bool config FOO bool default n With this change, neither of these will generate a '# CONFIG_FOO is not set' line (assuming FOO isn't selected/implied). That might make it clearer to people that a bare 'default n' is redundant. ... Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Jens Axboe

zram: introduce zram memory tracking

2018-06-08T00:34:34Z

zRam as swap is useful for small memory device. However, swap means those pages on zram are mostly cold pages due to VM's LRU algorithm. Especially, once init data for application are touched for launching, they tend to be not accessed any more and finally swapped out. zRAM can store such cold pages as compressed form but it's pointless to keep in memory. Better idea is app developers free them directly rather than remaining them on heap. This patch tell us last access time of each block of zram via "cat /sys/kernel/debug/zram/zram0/block_state". The output is as follows, 300 75.033841 .wh 301 63.806904 s.. 302 63.806919 ..h First column is zram's block index and 3rh one represents symbol (s: same page w: written page to backing store h: huge page) of the block state. Second column represents usec time unit of the block was last accessed. So above example means the 300th block is accessed at 75.033851 second and it was huge so it was written to the backing store. Admin can leverage this information to catch cold|incompressible pages of process with *pagemap* once part of heaps are swapped out. I used the feature a few years ago to find memory hoggers in userspace to notify them what memory they have wasted without touch for a long time. With it, they could reduce unnecessary memory space. However, at that time, I hacked up zram for the feature but now I need the feature again so I decided it would be better to upstream rather than keeping it alone. I hope I submit the userspace tool to use the feature soon. [akpm@linux-foundation.org: fix i386 printk warning] [minchan@kernel.org: use ktime_get_boottime() instead of sched_clock()] Link: http://lkml.kernel.org/r/20180420063525.GA253739@rodete-desktop-imager.corp.google.com [akpm@linux-foundation.org: documentation tweak] [akpm@linux-foundation.org: fix i386 printk warning] [minchan@kernel.org: fix compile warning] Link: http://lkml.kernel.org/r/20180508104849.GA8209@rodete-desktop-imager.corp.google.com [rdunlap@infradead.org: fix printk formats] Link: http://lkml.kernel.org/r/3652ccb1-96ef-0b0b-05d1-f661d7733dcc@infradead.org Link: http://lkml.kernel.org/r/20180416090946.63057-5-minchan@kernel.org Signed-off-by: Minchan Kim Signed-off-by: Randy Dunlap Reviewed-by: Sergey Senozhatsky Acked-by: Greg Kroah-Hartman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds