linux-kernel - Re: [PATCH v15 0/7] mm / virtio: Provide support for free page reporting

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Date:   Thu, 12 Dec 2019 15:47:18 -0800
From:   Alexander Duyck <alexander.h.duyck@...ux.intel.com>
To:     Alexander Duyck <alexander.duyck@...il.com>, kvm@...r.kernel.org,
        mst@...hat.com, linux-kernel@...r.kernel.org, willy@...radead.org,
        mhocko@...nel.org, linux-mm@...ck.org, akpm@...ux-foundation.org,
        mgorman@...hsingularity.net, vbabka@...e.cz
Cc:     yang.zhang.wz@...il.com, nitesh@...hat.com, konrad.wilk@...cle.com,
        david@...hat.com, pagupta@...hat.com, riel@...riel.com,
        lcapitulino@...hat.com, dave.hansen@...el.com,
        wei.w.wang@...el.com, aarcange@...hat.com, pbonzini@...hat.com,
        dan.j.williams@...el.com, osalvador@...e.de
Subject: Re: [PATCH v15 0/7] mm / virtio: Provide support for free page
 reporting

On Thu, 2019-12-05 at 08:22 -0800, Alexander Duyck wrote:
> This series provides an asynchronous means of reporting free guest pages
> to a hypervisor so that the memory associated with those pages can be
> dropped and reused by other processes and/or guests on the host. Using
> this it is possible to avoid unnecessary I/O to disk and greatly improve
> performance in the case of memory overcommit on the host.

<snip>

> Changes from v14:
> https://lore.kernel.org/lkml/20191119214454.24996.66289.stgit@localhost.localdomain/
> Renamed "unused page reporting" to "free page reporting"
>   Updated code, kconfig, and patch descriptions
> Split out patch for __free_isolated_page
>   Renamed function to __putback_isolated_page
> Rewrote core reporting functionality
>   Added logic to reschedule worker in 2 seconds instead of run to completion
>   Removed reported_pages statistics
>   Removed REPORTING_REQUESTED bit used in zone flags
>   Replaced page_reporting_dev_info refcount with state variable
>   Removed scatterlist from page_reporting_dev_info
>   Removed capacity from page reporting device
>   Added dynamic scatterlist allocation/free at start/end of reporting process
>   Updated __free_one_page so that reported pages are not always added to tail
>   Added logic to handle error from report function
> Updated virtio-balloon patch that adds support for page reporting
>   Updated patch description to try and highlight differences in approaches
>   Updated logic to reflect that we cannot limit the scatterlist from device
>   Added logic to return error from report function
> Moved documentation patch to end of patch set

It has been about a week since I posted v15 and haven't heard anything.
Consider this a gentle ping.

I'm looking for input on patches 3 and 4 in this set as I updated them to
address most of the concerns Mel had. Just wondering if the set needs
additional work or if we are good with this as a starting point for this
feature?

Thanks.

- Alex