On Tue, Oct 18, 2016 at 03:12:45PM +0800, zhouxianr...@huawei.com wrote:
> From: z00281421 <z00281...@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 <z00281...@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

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