linux-kernel - Re: [PATCH -mm -v4 03/21] mm, THP, swap: Support PMD swap mapping in swap

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Date:   Wed, 11 Jul 2018 08:59:40 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        "Shaohua Li" <shli@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Daniel Jordan <daniel.m.jordan@...cle.com>
Subject: Re: [PATCH -mm -v4 03/21] mm, THP, swap: Support PMD swap mapping in swap_duplicate()

Dave Hansen <dave.hansen@...ux.intel.com> writes:

>> Yes.  Boolean parameter isn't good at most times.  Matthew Wilcox
>> suggested to use
>> 
>>         swap_duplicate(&entry, HPAGE_PMD_NR);
>> 
>> vs.
>> 
>>         swap_duplicate(&entry, 1);
>> 
>> He thinks this makes the interface more flexible to support other swap
>> entry size in the future.  What do you think about that?
>
> That looks great to me too.
>
>>>>  		if (likely(!non_swap_entry(entry))) {
>>>> -			if (swap_duplicate(entry) < 0)
>>>> +			if (swap_duplicate(&entry, false) < 0)
>>>>  				return entry.val;
>>>>  
>>>>  			/* make sure dst_mm is on swapoff's mmlist. */
>>>
>>> I'll also point out that in a multi-hundred-line patch, adding arguments
>>> to a existing function would not be something I'd try to include in the
>>> patch.  I'd break it out separately unless absolutely necessary.
>> 
>> You mean add another patch, which only adds arguments to the function,
>> but not change the body of the function?
>
> Yes.  Or, just add the non-THP-swap version first.

OK, will do this.

Best Regards,
Huang, Ying