From: Andrew Morton <akpm@linux-foundation.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Rik van Riel <riel@surriel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Michal Hocko <mhocko@suse.com>,
"kirill.shutemov" <kirill.shutemov@linux.intel.com>,
Minchan Kim <minchan@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
kernel-team <kernel-team@fb.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Nadav Amit <nadav.amit@gmail.com>
Subject: Re: mm,tlb: revert 4647706ebeee?
Date: Mon, 9 Jul 2018 17:13:56 -0700 [thread overview]
Message-ID: <20180709171356.87d834e125f06e0cdaa72f85@linux-foundation.org> (raw)
In-Reply-To: <20180708012538.51b2c672@roar.ozlabs.ibm.com>
On Sun, 8 Jul 2018 01:25:38 +1000 Nicholas Piggin <npiggin@gmail.com> wrote:
> On Fri, 06 Jul 2018 13:03:55 -0400
> Rik van Riel <riel@surriel.com> wrote:
>
> > Hello,
> >
> > It looks like last summer, there were 2 sets of patches
> > in flight to fix the issue of simultaneous mprotect/madvise
> > calls unmapping PTEs, and some pages not being flushed from
> > the TLB before returning to userspace.
> >
> > Minchan posted these patches:
> > 56236a59556c ("mm: refactor TLB gathering API")
> > 99baac21e458 ("mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem")
> >
> > Around the same time, Mel posted:
> > 4647706ebeee ("mm: always flush VMA ranges affected by zap_page_range")
> >
> > They both appear to solve the same bug.
> >
> > Only one of the two solutions is needed.
> >
> > However, 4647706ebeee appears to introduce extra TLB
> > flushes - one per VMA, instead of one over the entire
> > range unmapped, and also extra flushes when there are
> > no simultaneous unmappers of the same mm.
> >
> > For that reason, it seems like we should revert
> > 4647706ebeee and keep only Minchan's solution in
> > the kernel.
> >
> > Am I overlooking any reason why we should not revert
> > 4647706ebeee?
>
> Yes I think so. Discussed here recently:
>
> https://marc.info/?l=linux-mm&m=152878780528037&w=2
Unclear if that was an ack ;)
> Actually we realized that powerpc does not implement the mmu
> gather flushing quite right so it needs a fix before this
> revert. But I propose the revert for next merge window.
Yes, I have Rik's patch for 4.19-rc1. I added yourself, Aneesh and
Nadav to cc so you'll see it fly past. If poss, please do get this all
tested before the time comes and let me know?
next prev parent reply other threads:[~2018-07-10 0:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-06 17:03 Rik van Riel
2018-07-06 17:10 ` [PATCH] Revert "mm: always flush VMA ranges affected by zap_page_range" Rik van Riel
2018-07-16 13:12 ` Mel Gorman
2018-07-07 15:25 ` mm,tlb: revert 4647706ebeee? Nicholas Piggin
2018-07-10 0:13 ` Andrew Morton [this message]
2018-07-10 5:04 ` Nicholas Piggin
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