linux-kernel - Re: [PATCH 4/4] percpu: use reclaim threshold instead of running for every page

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Message-ID: <YH9GN/EbGE5yf+CO@carbon.dhcp.thefacebook.com>
Date:   Tue, 20 Apr 2021 14:23:03 -0700
From:   Roman Gushchin <guro@...com>
To:     Dennis Zhou <dennis@...nel.org>
CC:     Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] percpu: use reclaim threshold instead of running for
 every page

On Mon, Apr 19, 2021 at 10:50:47PM +0000, Dennis Zhou wrote:
> The last patch implements reclaim by adding 2 additional lists where a
> chunk's lifecycle is:
>   active_slot -> to_depopulate_slot -> sidelined_slot
> 
> This worked great because we're able to nicely converge paths into
> isolation. However, it's a bit aggressive to run for every free page.
> Let's accumulate a few free pages before we do this. To do this, the new
> lifecycle is:
>   active_slot -> sidelined_slot -> to_depopulate_slot -> sidelined_slot
> 
> The transition from sidelined_slot -> to_depopulate_slot occurs on a
> threshold instead of before where it directly went to the
> to_depopulate_slot. pcpu_nr_isolated_empty_pop_pages[] is introduced to
> aid with this.
> 
> Suggested-by: Roman Gushchin <guro@...com>
> Signed-off-by: Dennis Zhou <dennis@...nel.org>

Acked-by: Roman Gushchin <guro@...com>

Thanks, Dennis!