linux-kernel - Re: [PATCH 3/8] migrate_pages: restrict number of pages to migrate in batch

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Message-ID: <87pmbvno43.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Wed, 04 Jan 2023 08:24:12 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Zi Yan <ziy@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, Yang Shi <shy828301@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Oscar Salvador <osalvador@...e.de>,
        "Matthew Wilcox" <willy@...radead.org>,
        Bharata B Rao <bharata@....com>,
        "Alistair Popple" <apopple@...dia.com>,
        haoxin <xhao@...ux.alibaba.com>
Subject: Re: [PATCH 3/8] migrate_pages: restrict number of pages to migrate
 in batch

Zi Yan <ziy@...dia.com> writes:

> On 26 Dec 2022, at 19:28, Huang Ying wrote:

[snip]

>> +/*
>> + * migrate_pages - migrate the folios specified in a list, to the free folios
>> + *		   supplied as the target for the page migration
>> + *
>> + * @from:		The list of folios to be migrated.
>> + * @get_new_page:	The function used to allocate free folios to be used
>> + *			as the target of the folio migration.
>> + * @put_new_page:	The function used to free target folios if migration
>> + *			fails, or NULL if no special handling is necessary.
>> + * @private:		Private data to be passed on to get_new_page()
>> + * @mode:		The migration mode that specifies the constraints for
>> + *			folio migration, if any.
>> + * @reason:		The reason for folio migration.
>> + * @ret_succeeded:	Set to the number of folios migrated successfully if
>> + *			the caller passes a non-NULL pointer.
>> + *
>> + * The function returns after 10 attempts or if no folios are movable any more
>> + * because the list has become empty or no retryable folios exist any more.
>> + * It is caller's responsibility to call putback_movable_pages() to return folios
>> + * to the LRU or free list only if ret != 0.
>> + *
>> + * Returns the number of {normal folio, large folio, hugetlb} that were not
>> + * migrated, or an error code. The number of large folio splits will be
>> + * considered as the number of non-migrated large folio, no matter how many
>> + * split folios of the large folio are migrated successfully.
>> + */
>> +int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> +		free_page_t put_new_page, unsigned long private,
>> +		enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
>> +{
>> +	int rc, rc_gether;
>
> rc_gether -> rc_gather?

Good catch!  Thanks!  Will change this in the next version.

Best Regards,
Huang, Ying

>> +	int nr_pages;
>> +	struct folio *folio, *folio2;
>> +	LIST_HEAD(folios);
>> +	LIST_HEAD(ret_folios);
>> +	struct migrate_pages_stats stats;
>> +

[snip]