Messages in this thread | | | From | Minchan Kim <> | Subject | [PATCH v2 0/4] zram memory tracking | Date | Tue, 27 Mar 2018 15:50:29 +0900 |
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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. As well, it's pointless to store incompressible pages to zram so better idea is app developers manages them directly like free or mlock rather than remaining them on heap.
This patch provides a debugfs /sys/kernel/debug/zram/zram0/block_state to represent each block's state so admin can investigate what memory is cold|incompressible|same page with using pagemap once the pages are swapped out.
The output is as follows,
25064 .wh 100 25065 s.. 9 25067 ..h 15
First column is zram's block index and second one represents symbol (s: same page w: written page to backing store h: huge page) of the block state. Last one means number of seconds elapsed since the block was last accessed. So above example means the 25064th block is accessed 100 second ago and it was huge so it was written to the backing store.
* From v1: * Do not propagate error number for debugfs fail - Greg KH * Add writeback and hugepage information - Sergey
Minchan Kim (4): zram: correct flag name of ZRAM_ACCESS zram: mark incompressible page as ZRAM_HUGE zram: record accessed second zram: introduce zram memory tracking
Documentation/blockdev/zram.txt | 1 + drivers/block/zram/Kconfig | 10 ++ drivers/block/zram/zram_drv.c | 157 +++++++++++++++++++++++++++++--- drivers/block/zram/zram_drv.h | 12 ++- 4 files changed, 163 insertions(+), 17 deletions(-)
-- 2.17.0.rc0.231.g781580f067-goog
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