| 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
| ||
|
Message-ID: <CAGsJ_4yRq6iBPpWLdbcknGLGUCEBDsc05rAeMuK8HRAwnpg2Zg@mail.gmail.com>
Date: Wed, 16 Apr 2025 15:48:40 +0800
From: Barry Song <21cnbao@...il.com>
To: Zi Yan <ziy@...dia.com>, Tangquan Zheng <zhengtangquan@...o.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Barry Song <v-songbaohua@...o.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>, David Hildenbrand <david@...hat.com>,
Johannes Weiner <hannes@...xchg.org>, Matthew Wilcox <willy@...radead.org>,
Oscar Salvador <osalvador@...e.de>, Ryan Roberts <ryan.roberts@....com>
Subject: Re: [RFC PATCH] mm: don't promote exclusive file folios of dying processes
On Sun, Apr 13, 2025 at 12:31 AM Zi Yan <ziy@...dia.com> wrote:
>
> On 12 Apr 2025, at 4:58, Barry Song wrote:
>
> > From: Barry Song <v-songbaohua@...o.com>
> >
> > Promoting exclusive file folios of a dying process is unnecessary and
> > harmful. For example, while Firefox is killed and LibreOffice is
> > launched, activating Firefox's young file-backed folios makes it
> > harder to reclaim memory that LibreOffice doesn't use at all.
> >
> > An exiting process is unlikely to be restarted right away—it's
> > either terminated by the user or killed by the OOM handler.
>
> The proposal looks reasonable to me. Do you have any performance number
> about the improvement?
Tangquan ran the test on Android phones and saw 3% improvement on
refault/thrashing things:
w/o patch w/patch
workingset_refault_anon 2215933 2146602 3.13%
workingset_refault_file 9859208 9646518 2.16%
pswpin 2411086 2337790 3.04%
pswpout 6482838 6264865 3.36%
A further demotion of exclusive file folios can improvement more, but
might be controversial. it could be a separate patch later.
>
> >
> > Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
> > Cc: David Hildenbrand <david@...hat.com>
> > Cc: Johannes Weiner <hannes@...xchg.org>
> > Cc: Matthew Wilcox (Oracle) <willy@...radead.org>
> > Cc: Oscar Salvador <osalvador@...e.de>
> > Cc: Ryan Roberts <ryan.roberts@....com>
> > Cc: Zi Yan <ziy@...dia.com>
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
> > ---
> > mm/huge_memory.c | 4 ++--
> > mm/internal.h | 19 +++++++++++++++++++
> > mm/memory.c | 9 ++++++++-
> > 3 files changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index e97a97586478..05b83d2fcbb6 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2264,8 +2264,8 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> > * Use flush_needed to indicate whether the PMD entry
> > * is present, instead of checking pmd_present() again.
> > */
> > - if (flush_needed && pmd_young(orig_pmd) &&
> > - likely(vma_has_recency(vma)))
> > + if (!exclusive_folio_of_dying_process(folio, vma) && flush_needed &&
> > + pmd_young(orig_pmd) && likely(vma_has_recency(vma)))
> > folio_mark_accessed(folio);
> > }
> >
> > diff --git a/mm/internal.h b/mm/internal.h
> > index 4e0ea83aaf1c..666de96a293d 100644
> > --- a/mm/internal.h
> > +++ b/mm/internal.h
> > @@ -11,6 +11,7 @@
> > #include <linux/khugepaged.h>
> > #include <linux/mm.h>
> > #include <linux/mm_inline.h>
> > +#include <linux/oom.h>
> > #include <linux/pagemap.h>
> > #include <linux/pagewalk.h>
> > #include <linux/rmap.h>
> > @@ -130,6 +131,24 @@ static inline int folio_nr_pages_mapped(const struct folio *folio)
> > return atomic_read(&folio->_nr_pages_mapped) & FOLIO_PAGES_MAPPED;
> > }
> >
> > +/*
> > + * Return true if a folio is exclusive and belongs to an exiting or
> > + * oom-reaped process; otherwise, return false.
> > + */
> > +static inline bool exclusive_folio_of_dying_process(struct folio *folio,
> > + struct vm_area_struct *vma)
> > +{
> > + if (folio_maybe_mapped_shared(folio))
> > + return false;
> > +
> > + if (!atomic_read(&vma->vm_mm->mm_users))
> > + return true;
> > + if (check_stable_address_space(vma->vm_mm))
> > + return true;
> > +
> > + return false;
> > +}
> > +
> > /*
> > * Retrieve the first entry of a folio based on a provided entry within the
> > * folio. We cannot rely on folio->swap as there is no guarantee that it has
> > diff --git a/mm/memory.c b/mm/memory.c
> > index b9e8443aaa86..cab69275e473 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -1515,7 +1515,14 @@ static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb,
> > *force_flush = true;
> > }
> > }
> > - if (pte_young(ptent) && likely(vma_has_recency(vma)))
> > +
> > + /*
> > + * Skip marking exclusive file folios as accessed for processes that are
> > + * exiting or have been reaped due to OOM. This prevents unnecessary
> > + * promotion of folios that won't benefit the new process being launched.
> > + */
> > + if (!exclusive_folio_of_dying_process(folio, vma) && pte_young(ptent) &&
> > + likely(vma_has_recency(vma)))
> > folio_mark_accessed(folio);
> > rss[mm_counter(folio)] -= nr;
> > } else {
> > --
> > 2.39.3 (Apple Git-146)
>
>
> --
> Best Regards,
> Yan, Zi
Thanks
Barry
Powered by blists - more mailing lists