linux-kernel - Re: [PATCH v6 7/9] mm: multigenerational lru: eviction

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Date:   Wed, 12 Jan 2022 01:05:51 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hillf Danton <hdanton@...a.com>, Jens Axboe <axboe@...nel.dk>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Michael Larabel <Michael@...haellarabel.com>,
        Michal Hocko <mhocko@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Will Deacon <will@...nel.org>,
        Ying Huang <ying.huang@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        page-reclaim@...gle.com, x86@...nel.org,
        Konstantin Kharlamov <Hi-Angel@...dex.ru>
Subject: Re: [PATCH v6 7/9] mm: multigenerational lru: eviction

On Tue, Jan 11, 2022 at 04:07:57PM +0530, Aneesh Kumar K.V wrote:
> ...
> 
>  +static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
> > +			  int *type_scanned, struct list_head *list)
> > +{
> > +	int i;
> > +	int type;
> > +	int scanned;
> > +	int tier = -1;
> > +	DEFINE_MIN_SEQ(lruvec);
> > +
> > +	VM_BUG_ON(!seq_is_valid(lruvec));
> > +
> > +	/*
> > +	 * Try to make the obvious choice first. When anon and file are both
> > +	 * available from the same generation, interpret swappiness 1 as file
> > +	 * first and 200 as anon first.
> > +	 */
> > +	if (!swappiness)
> > +		type = 1;
> > +	else if (min_seq[0] < min_seq[1])
> > +		type = 0;
> > +	else if (swappiness == 1)
> > +		type = 1;
> > +	else if (swappiness == 200)
> > +		type = 0;
> > +	else
> > +		type = get_type_to_scan(lruvec, swappiness, &tier);
> > +
> 
> Wondering wether it will make it simpler to use
> #define ANON 0
> #define FILE 1
> 
> and then
> 	else if (min_seq[ANON] < min_seq[FILE])
> 		type = ANON;
> 
> The usage of 0/1 across code do confuse

I agree, and I plan to do this later because the existing code uses
this convention and needs renaming too.