lkml.org 
[lkml]   [2019]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v15 0/7] mm / virtio: Provide support for free page reporting
    On Fri, Dec 13, 2019 at 11:00:42AM +0100, David Hildenbrand wrote:
    > > A brief history on the background of free page reporting can be found at:
    > > https://lore.kernel.org/lkml/29f43d5796feed0dec8e8bb98b187d9dac03b900.camel@linux.intel.com/
    > >
    > > Changes from v13:
    > > https://lore.kernel.org/lkml/20191105215940.15144.65968.stgit@localhost.localdomain/
    > > Rewrote core reporting functionality
    > > Merged patches 3 & 4
    > > Dropped boundary list and related code
    > > Folded get_reported_page into page_reporting_fill
    > > Folded page_reporting_fill into page_reporting_cycle
    > > Pulled reporting functionality out of free_reported_page
    > > Renamed it to __free_isolated_page
    > > Moved page reporting specific bits to page_reporting_drain
    > > Renamed phdev to prdev since we aren't "hinting" we are "reporting"
    > > Added documentation to describe the usage of unused page reporting
    > > Updated cover page and patch descriptions to avoid mention of boundary
    > >
    > > 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
    >
    > Last time Mel said
    >
    > "Ok, I'm ok with how this hooks into the allocator as the overhead is
    > minimal. However, the patch itself still includes a number of
    > optimisations instead of being a bare-boned implementation of the
    > feature with optimisations layered on top."
    >

    I didn't get the chance to take a close look as I'm trying to clear as
    much as possible from my table on the run-up to Christmas so I don't come
    back to a disaster inbox. I also noted that the Acks for earlier patches
    were not included so I was uncertain if doing a full review would still
    be a good use of time when time was tight.

    That said, some optimisations are still included but much reduced. For
    example, list rotations are still there but it's very straight-forward.
    The refcount is gone which is good and replaced by a state, which could be
    be better documented, but is more straight forward and the zone->lock is
    back protecting the free lists primarily and not zone metadata or prdev
    metadata (at least not obviously). I didn't put in the time to see if
    the atomic_set in page_reporting_process() is ok or whether state could
    be lost but I *think* it's ok because it should be called from just one
    workqueue request and they shouldn't be stacked. A comment there explaining
    why atomic_set is definitely correct would be helpful.

    I'm inclined to decide that yes, this version is potentially ok as a
    bare minimum but didn't put in the time to be 100% sure.

    --
    Mel Gorman
    SUSE Labs

    \
     
     \ /
      Last update: 2019-12-13 12:09    [W:4.109 / U:0.216 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site