linux-kernel - Re: [PATCH v2 1/2] mm:vmscan: the dirty folio in folio

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Message-ID: <ZTZlR2qJivLIdgsB@casper.infradead.org>
Date:   Mon, 23 Oct 2023 13:21:27 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     zhiguojiang <justinjiang@...o.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, opensource.kernel@...o.com
Subject: Re: [PATCH v2 1/2] mm:vmscan: the dirty folio in folio_list skip
 unmap

On Mon, Oct 23, 2023 at 04:07:28PM +0800, zhiguojiang wrote:
> > Are you seeing measurable changes for any workloads?  It certainly seems
> > like you should, but it would help if you chose a test from mmtests and
> > showed how performance changed on your system.
> In one mmtest, the max times for a invalid recyling of a folio_list dirty
> folio that does not support pageout and has been activated in
> shrink_folio_list() are: cost=51us, exe=2365us.
> 
> Calculate according to this formula: dirty_cost / total_cost * 100%, the
> recyling efficiency of dirty folios can be improved 53.13%、82.95%.
> 
> So this patch can optimize shrink efficiency and reduce the workload of
> kswapd to a certain extent.
> 
> kswapd0-96      (     96) [005] .....   387.218548:
> mm_vmscan_lru_shrink_inactive: [Justin] nid 0 nr_scanned 32 nr_taken 32
> nr_reclaimed 31 nr_dirty  1 nr_unqueued_dirty  1 nr_writeback 0
> nr_activate[1]  1 nr_ref_keep  0 f RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
> total_cost 96 total_exe 2365 dirty_cost 51 total_exe 2365
> 
> kswapd0-96      (     96) [006] .....   412.822532:
> mm_vmscan_lru_shrink_inactive: [Justin] nid 0 nr_scanned 32 nr_taken 32
> nr_reclaimed  0 nr_dirty 32 nr_unqueued_dirty 32 nr_writeback 0
> nr_activate[1] 19 nr_ref_keep 13 f RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
> total_cost 88 total_exe 605  dirty_cost 73 total_exe 605

I appreciate that you can put probes in and determine the cost, but do
you see improvements for a real workload?  Like doing a kernel compile
-- does it speed up at all?