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Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark()

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On (02/22/16 09:04), Minchan Kim wrote:
[..]
> max_zpage_size was there since zram's grandpa(ie, ramzswap).
> AFAIR, at that time, it works to forward incompressible
> (e.g, PAGE_SIZE/2) page to backing swap if it presents.
> If it doesn't have any backing swap and it's incompressbile
> (e.g, PAGE_SIZE*3/4), it stores it as uncompressed page
> to avoid *decompress* overhead later.

"PAGE_SIZE * 3 / 4" introduces a bigger memory overhead than
decompression of 3K bytes later.

> And Nitin want to make it as tunable parameter. I agree the
> approach because I don't want to make coupling between zram
> and allocator as far as possible.
> 
> If huge class is pain

they are.

> it's allocator problem, not zram stuff.

the allocator's problems start at the point where zram begins to have
opinion on what should be stored as ->huge object and what should not.
it's not up to zram to enforce this.


> I think we should try to remove such problem in zsmalloc layer,
> firstly.

zram asks to store a PAGE_SIZE sized object, what zsmalloc can
possible do about this?


> Having said that, I agree your claim that uncompressible pages
> are pain. I want to handle the problem as multiple-swap apparoach.

zram is not just for swapping. as simple as that.


and enforcing a multi-swap approach on folks who use zram for swap
doesn't look right to me.


> For that, we should introduce new knob in zram layer like Nitin
> did and make it configurable so we could solve the problem of
> single zram-swap system as well as multiple swap system.

a 'bad compression' watermark knob? isn't it an absolutely low level
thing no one ever should see?

	-ss

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[RFC][PATCH v2 0/3] mm/zsmalloc: increase objects density and reduce memory wastage Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-21 18:30 +0100
  [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-21 18:50 +0100
    Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Minchan Kim <minchan@kernel.org> - 2016-02-22 01:10 +0100
      Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 01:40 +0100
        Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Minchan Kim <minchan@kernel.org> - 2016-02-22 02:30 +0100
          Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 03:00 +0100
            Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 03:10 +0100
            Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Minchan Kim <minchan@kernel.org> - 2016-02-22 04:00 +0100
              Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 05:00 +0100
                Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Minchan Kim <minchan@kernel.org> - 2016-02-22 06:00 +0100
                Re: [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 06:10 +0100
  [RFC][PATCH v2 1/3] mm/zsmalloc: introduce zs_get_huge_class_size_watermark() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-21 19:50 +0100
  [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-21 20:00 +0100
    Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Minchan Kim <minchan@kernel.org> - 2016-02-22 01:30 +0100
      Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 01:50 +0100
        Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Minchan Kim <minchan@kernel.org> - 2016-02-22 02:40 +0100
          Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 03:10 +0100
            Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Minchan Kim <minchan@kernel.org> - 2016-02-22 03:40 +0100
              Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 05:00 +0100
                Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Minchan Kim <minchan@kernel.org> - 2016-02-22 05:50 +0100
                Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 11:50 +0100
          Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-22 03:30 +0100

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