LWN: Comments on "LRU-list manipulation with DAMON"

LRU-list manipulation with DAMON

karim96 — Mon, 02 Jan 2023 02:40:50 +0000

> When this happens, the pages are "deactivated", meaning that they are marked in the page tables as "not present". Should some process try to access such a page, a soft page fault will result

This is wrong. Pages moved to inactive LRU lists are never marked "not present" in process page tables and page faults never happen on such pages.

Pages in the inactive lists get promoted back to the active lists if the page scan done by the reclaim subsystem finds out that the "accessed bit" for those pages was set since the last scan.

LRU-list manipulation with DAMON

jezuch — Sat, 27 Aug 2022 06:20:15 +0000

I would also add that PL-RUS relations are a little strained right now.

*ducks*

LRU-list manipulation with DAMON

zev — Thu, 25 Aug 2022 21:26:40 +0000

Author SeongJae Park calls this mechanism "proactive LRU-list sorting" or PLRUS.

 _______________________________________ 
/ I, for one, wish it were "work-ahead" \
\ instead of "proactive".               /
 --------------------------------------- 
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     (          '  |'        ( __= ___..-._ ( (.\\
    ('\      .___ ___.      /'.___=          \.\.\
     \\\-..____________..-''

LRU-list manipulation with DAMON

linusw — Tue, 23 Aug 2022 13:15:27 +0000

In a review of the hardware prefetch control registers that some architectures offer, I pointed to DAMON suggesting its statistics to be elegible to drive the prefetch control for a somewhat heuristic/scientific method rather than the trial-and-error method apparently currently used for these knobs, I don't know if there is something to it, but I hope I'm not all wrong.

https://lore.kernel.org/linux-arm-kernel/20220607120530.2...