linux-kernel - Re: [PATCH] mm: vmscan: correct nr

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3a919cba-fefe-d78e-313a-8f0d81a4a75d@linux.alibaba.com>
Date:   Fri, 10 May 2019 09:50:04 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Matthew Wilcox <willy@...radead.org>,
        "Huang, Ying" <ying.huang@...el.com>
Cc:     hannes@...xchg.org, mhocko@...e.com, mgorman@...hsingularity.net,
        kirill.shutemov@...ux.intel.com, hughd@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP



On 5/10/19 9:36 AM, Matthew Wilcox wrote:
> On Fri, May 10, 2019 at 10:12:40AM +0800, Huang, Ying wrote:
>>> +		nr_reclaimed += (1 << compound_order(page));
>> How about to change this to
>>
>>
>>          nr_reclaimed += hpage_nr_pages(page);
> Please don't.  That embeds the knowledge that we can only swap out either
> normal pages or THP sized pages.  I'm trying to make the VM capable of
> supporting arbitrary-order pages, and this would be just one more place
> to fix.
>
> I'm sympathetic to the "self documenting" argument.  My current tree has
> a patch in it:
>
>      mm: Introduce compound_nr
>      
>      Replace 1 << compound_order(page) with compound_nr(page).  Minor
>      improvements in readability.
>
> It goes along with this patch:
>
>      mm: Introduce page_size()
>
>      It's unnecessarily hard to find out the size of a potentially huge page.
>      Replace 'PAGE_SIZE << compound_order(page)' with page_size(page).

So you prefer keeping using  "1 << compound_order" as v1 did? Then you 
will convert all "1 << compound_order" to compound_nr?

>
> Better suggestions on naming gratefully received.  I'm more happy with
> page_size() than I am with compound_nr().  page_nr() gives the wrong
> impression; page_count() isn't great either.