linux-kernel - Re: [PATCH -v2 0/9] migrate

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Message-ID: <87tu0rqaiv.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 16 Jan 2023 14:05:44 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Zi Yan <ziy@...dia.com>,
        Yang Shi <shy828301@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Oscar Salvador <osalvador@...e.de>,
        Bharata B Rao <bharata@....com>,
        Alistair Popple <apopple@...dia.com>,
        haoxin <xhao@...ux.alibaba.com>
Subject: Re: [PATCH -v2 0/9] migrate_pages(): batch TLB flushing

Matthew Wilcox <willy@...radead.org> writes:

> On Fri, Jan 13, 2023 at 10:42:08AM +0800, Huang, Ying wrote:
>> +++ b/mm/migrate.c
>> @@ -1187,10 +1187,13 @@ static int __migrate_folio_move(struct folio *src, struct folio *dst,
>>  	int rc;
>>  	int page_was_mapped = 0;
>>  	struct anon_vma *anon_vma = NULL;
>> +	bool is_lru = !__PageMovable(&src->page);
>>  
>>  	__migrate_folio_extract(dst, &page_was_mapped, &anon_vma);
>>  
>>  	rc = move_to_new_folio(dst, src, mode);
>> +	if (!unlikely(is_lru))
>> +		goto out_unlock_both;
>
> This reads a little awkwardly.  Could it be:
>
> 	if (likely(!is_lru))
>
> ... but honestly, I think the polarity here is wrong.  LRU pages tend to
> outnumber !LRU pages, so shouldn't this be:
>
> 	if (unlikely(!is_lru)) {
>
> just like it is in migrate_folio_unmap()?

Yes.  Thank you very much for pointing this out.  Will fix it for the
next version.

Best Regards,
Huang, Ying