linux-kernel - Re: [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CAOUHufbiSShp=khZFL6BmJKNNkG-LBrsPoLwYxewcgtZhi5tFg@mail.gmail.com>
Date:   Fri, 18 Mar 2022 21:11:09 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Barry Song <21cnbao@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Aneesh Kumar <aneesh.kumar@...ux.ibm.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>,
        Mike Rapoport <rppt@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Will Deacon <will@...nel.org>,
        Ying Huang <ying.huang@...el.com>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Kernel Page Reclaim v2 <page-reclaim@...gle.com>,
        x86 <x86@...nel.org>, Brian Geffon <bgeffon@...gle.com>,
        Jan Alexander Steffens <heftig@...hlinux.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Steven Barrett <steven@...uorix.net>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Daniel Byrne <djbyrne@....edu>,
        Donald Carr <d@...os-reins.com>,
        Holger Hoffstätte <holger@...lied-asynchrony.com>,
        Konstantin Kharlamov <Hi-Angel@...dex.ru>,
        Shuang Zhai <szhai2@...rochester.edu>,
        Sofia Trinh <sofia.trinh@....works>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>
Subject: Re: [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation

On Fri, Mar 18, 2022 at 9:01 PM Barry Song <21cnbao@...il.com> wrote:
>
> > +static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
> > +{
> > +       unsigned long old_flags, new_flags;
> > +       int type = folio_is_file_lru(folio);
> > +       struct lru_gen_struct *lrugen = &lruvec->lrugen;
> > +       int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
> > +
> > +       do {
> > +               new_flags = old_flags = READ_ONCE(folio->flags);
> > +               VM_BUG_ON_FOLIO(!(new_flags & LRU_GEN_MASK), folio);
> > +
> > +               new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
> > +               new_gen = (old_gen + 1) % MAX_NR_GENS;
>
> new_gen is assigned twice, i assume you mean
>                old_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
>                new_gen = (old_gen + 1) % MAX_NR_GENS;
>
> or do you always mean new_gen =  lru_gen_from_seq(min_seq) + 1?

Thanks a lot for your attention to details!

The first line should be in the next patch but I overlooked during the
last refactoring:

  new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
+ /* folio_update_gen() has promoted this page? */
+ if (new_gen >= 0 && new_gen != old_gen)
+ return new_gen;
+
  new_gen = (old_gen + 1) % MAX_NR_GENS;