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[5.15] Track PF uksmd patches #18

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@kakra kakra commented Nov 13, 2021 •
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@pfactum
mm/ksm: introduce ksm_madvise_merge() helper
d6839b7 
Move MADV_MERGEABLE part of ksm_madvise() into a dedicated helper since
it will be further used for marking VMAs to be merged forcibly.

This does not bring any functional changes.

Signed-off-by: Oleksandr Natalenko <[email protected]>
@pfactum
mm/ksm: introduce ksm_madvise_unmerge() helper
8dc9a4e 
Move MADV_UNMERGEABLE part of ksm_madvise() into a dedicated helper
since it will be further used for unmerging VMAs forcibly.

This does not bring any functional changes.

Signed-off-by: Oleksandr Natalenko <[email protected]>
@pfactum @kakra
mm/ksm, proc: introduce remote merge
94eaac1 
Present a per-process KSM knob to remotely mark anonymous
memory as mergeable.

To mark all the VMAs as mergeable, use:

   # echo merge > /proc/<pid>/ksm

To unmerge them, use:

   # echo unmerge > /proc/<pid>/ksm

Previously introduced ksm_madvise_*() helpers are used here.

Signed-off-by: Oleksandr Natalenko <[email protected]>
[backported KSM knob from 5.10]
Signed-off-by: Kai Krakow <[email protected]>
@pfactum @kakra
mm/ksm, proc: add remote KSM documentation
195c730 
Document respective /proc/<pid>/ksm knob.

Signed-off-by: Oleksandr Natalenko <[email protected]>
@kakra kakra mentioned this pull request Nov 13, 2021
Closed
@kakra kakra added the done To be superseded by next LTS label Dec 27, 2022
@kakra kakra closed this Mar 11, 2023
kakra pushed a commit that referenced this pull request May 31, 2025
@fatherMatrix @gregkh
dm: fix unconditional IO throttle caused by REQ_PREFLUSH
b55a97d 
[ Upstream commit 88f7f56 ]

When a bio with REQ_PREFLUSH is submitted to dm, __send_empty_flush()
generates a flush_bio with REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,
which causes the flush_bio to be throttled by wbt_wait().

An example from v5.4, similar problem also exists in upstream:

    crash> bt 2091206
    PID: 2091206  TASK: ffff2050df92a300  CPU: 109  COMMAND: "kworker/u260:0"
     #0 [ffff800084a2f7f0] __switch_to at ffff80004008aeb8
     #1 [ffff800084a2f820] __schedule at ffff800040bfa0c4
     #2 [ffff800084a2f880] schedule at ffff800040bfa4b4
     #3 [ffff800084a2f8a0] io_schedule at ffff800040bfa9c4
     #4 [ffff800084a2f8c0] rq_qos_wait at ffff8000405925bc
     #5 [ffff800084a2f940] wbt_wait at ffff8000405bb3a0
     #6 [ffff800084a2f9a0] __rq_qos_throttle at ffff800040592254
     #7 [ffff800084a2f9c0] blk_mq_make_request at ffff80004057cf38
     #8 [ffff800084a2fa60] generic_make_request at ffff800040570138
     #9 [ffff800084a2fae0] submit_bio at ffff8000405703b4
    #10 [ffff800084a2fb50] xlog_write_iclog at ffff800001280834 [xfs]
    #11 [ffff800084a2fbb0] xlog_sync at ffff800001280c3c [xfs]
    #12 [ffff800084a2fbf0] xlog_state_release_iclog at ffff800001280df4 [xfs]
    torvalds#13 [ffff800084a2fc10] xlog_write at ffff80000128203c [xfs]
    #14 [ffff800084a2fcd0] xlog_cil_push at ffff8000012846dc [xfs]
    #15 [ffff800084a2fda0] xlog_cil_push_work at ffff800001284a2c [xfs]
    #16 [ffff800084a2fdb0] process_one_work at ffff800040111d08
    #17 [ffff800084a2fe00] worker_thread at ffff8000401121cc
    #18 [ffff800084a2fe70] kthread at ffff800040118de4

After commit 2def284 ("xfs: don't allow log IO to be throttled"),
the metadata submitted by xlog_write_iclog() should not be throttled.
But due to the existence of the dm layer, throttling flush_bio indirectly
causes the metadata bio to be throttled.

Fix this by conditionally adding REQ_IDLE to flush_bio.bi_opf, which makes
wbt_should_throttle() return false to avoid wbt_wait().

Signed-off-by: Jinliang Zheng <[email protected]>
Reviewed-by: Tianxiang Peng <[email protected]>
Reviewed-by: Hao Peng <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
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@kakra @pfactum