From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Kalesh Singh <kaleshsingh@google.com>,
Nick Piggin <npiggin@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Christophe Leroy <christophe.leroy@csgroup.eu>
Subject: Re: [PATCH v5 7/9] mm/mremap: Move TLB flush outside page table lock
Date: Mon, 24 May 2021 19:54:08 +0530 [thread overview]
Message-ID: <87tumsqkfr.fsf@linux.ibm.com> (raw)
In-Reply-To: <CAHk-=whUHnm1CQ3LC0Qz=BBkhBRZkNW6ZmQZvSac2vju7gfeVg@mail.gmail.com>
Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Fri, May 21, 2021 at 3:04 AM Aneesh Kumar K.V
> <aneesh.kumar@linux.ibm.com> wrote:
>>
>> We could do MOVE_PMD with something like below? A equivalent MOVE_PUD
>> will be costlier which makes me wonder whether we should even support that?
>
> Well, without USE_SPLIT_PTE_PTLOCKS the pud case would be trivial too.
> But everybody uses split pte locks in practice.
>
> I get the feeling that the rmap code might have to use
> pud_lock/pmd_lock. I wonder how painful that would be.
>
Looking at this further, i guess we need to do the above to close the
race window. We do
static bool map_pte(struct page_vma_mapped_walk *pvmw)
{
pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
..
pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
spin_lock(pvmw->ptl);
}
That is we walk the table without holding the pte ptl. Hence we still
can race with the optimized PMD move.
-aneesh
next prev parent reply other threads:[~2021-05-24 14:24 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 5:43 [PATCH v5 0/9] Speedup mremap on ppc64 Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 1/9] selftest/mremap_test: Update the test to handle pagesize other than 4K Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 2/9] selftest/mremap_test: Avoid crash with static build Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 3/9] mm/mremap: Use pmd/pud_poplulate to update page table entries Aneesh Kumar K.V
2021-05-18 20:04 ` Nathan Chancellor
2021-05-19 4:46 ` Aneesh Kumar K.V
2021-05-19 18:02 ` Nathan Chancellor
2021-05-20 2:18 ` Peter Xu
2021-05-20 8:26 ` Aneesh Kumar K.V
2021-05-20 12:46 ` Peter Xu
2021-05-20 13:23 ` Aneesh Kumar K.V
2021-05-20 13:37 ` Aneesh Kumar K.V
2021-05-20 14:57 ` Peter Xu
2021-05-20 19:06 ` Zi Yan
2021-05-20 20:01 ` Peter Xu
2021-05-20 20:25 ` Kalesh Singh
2021-04-22 5:43 ` [PATCH v5 4/9] powerpc/mm/book3s64: Fix possible build error Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 5/9] powerpc/mm/book3s64: Update tlb flush routines to take a page walk cache flush argument Aneesh Kumar K.V
2021-05-15 16:35 ` Guenter Roeck
2021-05-15 20:41 ` Andrew Morton
2021-05-15 23:05 ` Guenter Roeck
2021-05-17 8:40 ` Aneesh Kumar K.V
2021-05-17 13:38 ` Guenter Roeck
2021-05-17 13:55 ` Aneesh Kumar K.V
2021-05-17 14:18 ` Guenter Roeck
2021-05-19 0:26 ` Michael Ellerman
2021-05-19 0:45 ` Segher Boessenkool
2021-05-19 12:03 ` Segher Boessenkool
2021-05-19 13:37 ` Guenter Roeck
2021-05-19 14:20 ` Segher Boessenkool
2021-05-19 15:28 ` Guenter Roeck
2021-05-20 7:37 ` Michael Ellerman
2021-05-20 12:17 ` Segher Boessenkool
2021-05-19 1:08 ` Guenter Roeck
2021-05-20 11:38 ` Michael Ellerman
2021-05-20 11:56 ` Guenter Roeck
2021-04-22 5:43 ` [PATCH v5 6/9] mm/mremap: Use range flush that does TLB and page walk cache flush Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 7/9] mm/mremap: Move TLB flush outside page table lock Aneesh Kumar K.V
2021-05-20 15:26 ` Aneesh Kumar K.V
2021-05-20 16:57 ` Aneesh Kumar K.V
2021-05-21 2:40 ` Linus Torvalds
2021-05-21 3:03 ` Aneesh Kumar K.V
2021-05-21 3:28 ` Aneesh Kumar K.V
2021-05-21 6:13 ` Linus Torvalds
2021-05-21 12:50 ` Aneesh Kumar K.V
2021-05-21 13:03 ` Aneesh Kumar K.V
2021-05-21 16:03 ` Linus Torvalds
2021-05-21 16:29 ` Aneesh Kumar K.V
2021-05-24 14:24 ` Aneesh Kumar K.V [this message]
2021-05-21 15:24 ` Liam Howlett
2021-05-21 16:02 ` Aneesh Kumar K.V
2021-05-21 16:05 ` Linus Torvalds
2021-04-22 5:43 ` [PATCH v5 8/9] mm/mremap: Allow arch runtime override Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 9/9] powerpc/mm: Enable move pmd/pud Aneesh Kumar K.V
2021-05-11 22:19 ` Andrew Morton
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