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SubjectRe: [Xen-devel] [PATCH v13 0/5] xenbus/backend: Add memory pressure handler callback
Date
Every patch of this patchset got at least one 'Reviewed-by' or 'Acked-by' from
appropriate maintainers by last Wednesday, and after that, got no comment yet.
May I ask some more comments?


Thanks,
SeongJae Park

On Wed, 18 Dec 2019 19:37:13 +0100 SeongJae Park <sjpark@amazon.com> wrote:

> Granting pages consumes backend system memory. In systems configured
> with insufficient spare memory for those pages, it can cause a memory
> pressure situation. However, finding the optimal amount of the spare
> memory is challenging for large systems having dynamic resource
> utilization patterns. Also, such a static configuration might lack
> flexibility.
>
> To mitigate such problems, this patchset adds a memory reclaim callback
> to 'xenbus_driver' (patch 1) and then introduce a lock for race
> condition avoidance (patch 2). After that, patch 3 applies the callback
> mechanism to mitigate the problem in 'xen-blkback'. The fourth and
> fifth patches are trivial cleanups; those fix nits we found during the
> development of this patchset.
>
> Note that patches 1, 4, and 5 are not changed since v9.
>
>
> Base Version
> ------------
>
> This patch is based on v5.4. A complete tree is also available at my
> public git repo:
> https://github.com/sjp38/linux/tree/patches/blkback/buffer_squeeze/v13
>
>
> Patch History
> -------------
>
> Changes from v12
> (https://lore.kernel.org/xen-devel/20191218104232.9606-1-sjpark@amazon.com/)
> - Do not unnecessarily disable interrupts (suggested by Juergen)
> - Hold lock from xenbus side (suggested by Juergen)
>
> Changes from v11
> (https://lore.kernel.org/xen-devel/20191217160748.693-2-sjpark@amazon.com/)
> - Fix wrong trylock use (reported by Juergen)
> - Merge patch 3 and 4 (suggested by Juergen)
> - Update test result
>
> Changes from v10
> (https://lore.kernel.org/xen-devel/20191216124527.30306-1-sjpark@amazon.com/)
> - Fix race condition (reported by SeongJae, suggested by Juergen)
>
> Changes from v9
> (https://lore.kernel.org/xen-devel/20191213153546.17425-1-sjpark@amazon.de/)
> - Add 'Reviewed-by' and 'Acked-by' from Roger Pau Monné
> - Update the commit message for overhead test of the 2nd path
>
> Changes from v8
> (https://lore.kernel.org/xen-devel/20191213130211.24011-1-sjpark@amazon.de/)
> - Drop 'Reviewed-by: Juergen' from the second patch
> (suggested by Roger Pau Monné)
> - Update contact of the new module param to SeongJae Park
> <sjpark@amazon.de>
> (suggested by Roger Pau Monné)
> - Wordsmith the description of the parameter
> (suggested by Roger Pau Monné)
> - Fix dumb bugs
> (suggested by Roger Pau Monné)
> - Move module param definition to xenbus.c and reduce the number of
> lines for this change
> (suggested by Roger Pau Monné)
> - Add a comment for the new callback, reclaim_memory, as other
> callbacks also have
> - Add another trivial cleanup of xenbus.c file (4th patch)
>
> Changes from v7
> (https://lore.kernel.org/xen-devel/20191211181016.14366-1-sjpark@amazon.de/)
> - Update sysfs-driver-xen-blkback for new parameter
> (suggested by Roger Pau Monné)
> - Use per-xen_blkif buffer_squeeze_end instead of global variable
> (suggested by Roger Pau Monné)
>
> Changes from v6
> (https://lore.kernel.org/linux-block/20191211042428.5961-1-sjpark@amazon.de/)
> - Remove more unnecessary prefixes (suggested by Roger Pau Monné)
> - Constify a variable (suggested by Roger Pau Monné)
> - Rename 'reclaim' into 'reclaim_memory' (suggested by Roger Pau Monné)
> - More wordsmith of the commit message (suggested by Roger Pau Monné)
>
> Changes from v5
> (https://lore.kernel.org/linux-block/20191210080628.5264-1-sjpark@amazon.de/)
> - Wordsmith the commit messages (suggested by Roger Pau Monné)
> - Change the reclaim callback return type (suggested by Roger Pau
> Monné)
> - Change the type of the blkback squeeze duration variable
> (suggested by Roger Pau Monné)
> - Add a patch for removal of unnecessary static variable name prefixes
> (suggested by Roger Pau Monné)
> - Fix checkpatch.pl warnings
>
> Changes from v4
> (https://lore.kernel.org/xen-devel/20191209194305.20828-1-sjpark@amazon.com/)
> - Remove domain id parameter from the callback (suggested by Juergen
> Gross)
> - Rename xen-blkback module parameter (suggested by Stefan Nuernburger)
>
> Changes from v3
> (https://lore.kernel.org/xen-devel/20191209085839.21215-1-sjpark@amazon.com/)
> - Add general callback in xen_driver and use it (suggested by Juergen
> Gross)
>
> Changes from v2
> (https://lore.kernel.org/linux-block/af195033-23d5-38ed-b73b-f6e2e3b34541@amazon.com)
> - Rename the module parameter and variables for brevity
> (aggressive shrinking -> squeezing)
>
> Changes from v1
> (https://lore.kernel.org/xen-devel/20191204113419.2298-1-sjpark@amazon.com/)
> - Adjust the description to not use the term, `arbitrarily`
> (suggested by Paul Durrant)
> - Specify time unit of the duration in the parameter description,
> (suggested by Maximilian Heyne)
> - Change default aggressive shrinking duration from 1ms to 10ms
> - Merge two patches into one single patch
>
>
> SeongJae Park (5):
> xenbus/backend: Add memory pressure handler callback
> xenbus/backend: Protect xenbus callback with lock
> xen/blkback: Squeeze page pools if a memory pressure is detected
> xen/blkback: Remove unnecessary static variable name prefixes
> xen/blkback: Consistently insert one empty line between functions
>
> .../ABI/testing/sysfs-driver-xen-blkback | 10 +++++
> drivers/block/xen-blkback/blkback.c | 42 +++++++++----------
> drivers/block/xen-blkback/common.h | 1 +
> drivers/block/xen-blkback/xenbus.c | 28 ++++++++++---
> drivers/xen/xenbus/xenbus_probe.c | 8 +++-
> drivers/xen/xenbus/xenbus_probe_backend.c | 38 +++++++++++++++++
> include/xen/xenbus.h | 3 ++
> 7 files changed, 103 insertions(+), 27 deletions(-)
>
> --
> 2.17.1
>

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