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Re: [PATCH] bdi flusher should not be throttled here when it fall into buddy slow path

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On Tue, Oct 18, 2016 at 03:12:45PM +0800, zhouxianrong@huawei.com wrote:
> From: z00281421 <z00281421@notesmail.huawei.com>
> 
> bdi flusher may enter page alloc slow path due to writepage and kmalloc. 
> in that case the flusher as a direct reclaimer should not be throttled here
> because it can not to reclaim clean file pages or anaonymous pages
> for next moment; furthermore writeback rate of dirty pages would be
> slow down and other direct reclaimers and kswapd would be affected.
> bdi flusher should be iosceduled by get_request rather than here.
> 
> Signed-off-by: z00281421 <z00281421@notesmail.huawei.com>

What does this patch do that PF_LESS_THROTTLE is not doing already if
there is an underlying BDI?

There have been a few patches like this recently that look like they might
do something useful but are subtle. They really should be accompanied by
a test case and data showing they either fix a functional issue (machine
livelocking due to writeback not making progress) or a performance issue.

-- 
Mel Gorman
SUSE Labs

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[PATCH] bdi flusher should not be throttled here when it fall into buddy slow path <zhouxianrong@huawei.com> - 2016-10-18 09:30 +0200
  Re: [PATCH] bdi flusher should not be throttled here when it fall into buddy slow path "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2016-10-18 11:40 +0200
  Re: [PATCH] bdi flusher should not be throttled here when it fall  into buddy slow path Mel Gorman <mgorman@techsingularity.net> - 2016-10-18 12:00 +0200
    Re: [PATCH] bdi flusher should not be throttled here when it fall  into buddy slow path zhouxianrong <zhouxianrong@huawei.com> - 2016-10-18 13:20 +0200
      Re: [PATCH] bdi flusher should not be throttled here when it fall  into buddy slow path Michal Hocko <mhocko@kernel.org> - 2016-10-18 13:50 +0200
  [PATCH] bdi flusher should not be throttled here when it fall into buddy slow path <zhouxianrong@huawei.com> - 2016-10-20 14:50 +0200
    Re: [PATCH] bdi flusher should not be throttled here when it fall  into buddy slow path Michal Hocko <mhocko@kernel.org> - 2016-10-20 15:30 +0200

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