From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org
Subject: Re: [PATCH -V1 06/24] powerpc: Reduce PTE table memory wastage
Date: Wed, 06 Mar 2013 10:33:16 +0530 [thread overview]
Message-ID: <877gll86i3.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <20130305021219.GC2888@iris.ozlabs.ibm.com>
Paul Mackerras <paulus@samba.org> writes:
> On Mon, Mar 04, 2013 at 04:28:42PM +0530, Aneesh Kumar K.V wrote:
>> The last one that ends up doing atomic_xor_bits which cause the mapcount
>> to go zero, will take the page off the list and free the page.
>
> No, look at the example again. page_table_free_rcu() won't take it
> off the list because it uses the (mask & FRAG_MASK) == 0 test, which
> fails (one fragment is still in use). page_table_free() won't take it
> off the list because it uses the mask == 0 test, which also fails (one
> fragment is still waiting for the RCU grace period). Finally,
> __page_table_free_rcu() doesn't take it off the list, it just frees
> the page. Oops. :)
How about the below
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -425,7 +425,7 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
bit = 1 << ((__pa(table) & ~PAGE_MASK) / PTE_FRAG_SIZE);
spin_lock(&mm->page_table_lock);
mask = atomic_xor_bits(&page->_mapcount, bit);
- if (mask == 0)
+ if (!(mask & FRAG_MASK))
list_del(&page->lru);
else if (mask & FRAG_MASK) {
/*
@@ -446,7 +446,7 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
ie, we always remove the page from the list, when the lower half is
zero or lower half is FRAG_MASK. We free the page when _mapcount is 0.
-aneesh
next prev parent reply other threads:[~2013-03-06 5:03 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-26 8:04 [PATCH -V1 00/24] THP support for PPC64 Aneesh Kumar K.V
2013-02-26 8:04 ` [PATCH -V1 01/24] powerpc: Use signed formatting when printing error Aneesh Kumar K.V
2013-02-26 8:04 ` [PATCH -V1 02/24] powerpc: Save DAR and DSISR in pt_regs on MCE Aneesh Kumar K.V
2013-02-26 8:04 ` [PATCH -V1 03/24] powerpc: Don't hard code the size of pte page Aneesh Kumar K.V
2013-02-27 23:09 ` Paul Mackerras
2013-02-26 8:04 ` [PATCH -V1 04/24] powerpc: Reduce the PTE_INDEX_SIZE Aneesh Kumar K.V
2013-02-26 8:04 ` [PATCH -V1 05/24] powerpc: Move the pte free routines from common header Aneesh Kumar K.V
2013-02-28 8:36 ` Paul Mackerras
2013-02-26 8:04 ` [PATCH -V1 06/24] powerpc: Reduce PTE table memory wastage Aneesh Kumar K.V
2013-03-04 4:58 ` Paul Mackerras
2013-03-04 10:58 ` Aneesh Kumar K.V
2013-03-04 23:36 ` Benjamin Herrenschmidt
2013-03-06 4:01 ` Aneesh Kumar K.V
2013-03-05 2:12 ` Paul Mackerras
2013-03-06 4:08 ` Aneesh Kumar K.V
2013-03-06 5:03 ` Aneesh Kumar K.V [this message]
2013-02-26 8:04 ` [PATCH -V1 07/24] powerpc: Add size argument to pgtable_cache_add Aneesh Kumar K.V
2013-03-04 5:13 ` Paul Mackerras
2013-03-04 11:02 ` Aneesh Kumar K.V
2013-03-05 1:50 ` Paul Mackerras
2013-03-06 4:23 ` Aneesh Kumar K.V
2013-02-26 8:04 ` [PATCH -V1 08/24] powerpc: Use encode avpn where we need only avpn values Aneesh Kumar K.V
2013-03-04 5:15 ` Paul Mackerras
2013-02-26 8:04 ` [PATCH -V1 09/24] powerpc: Decode the pte-lp-encoding bits correctly Aneesh Kumar K.V
2013-03-04 5:48 ` Paul Mackerras
2013-03-04 11:41 ` Aneesh Kumar K.V
2013-03-05 2:02 ` Paul Mackerras
2013-03-06 4:30 ` Aneesh Kumar K.V
2013-03-04 11:52 ` Aneesh Kumar K.V
2013-03-04 18:11 ` Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 10/24] powerpc: Return all the valid pte ecndoing in KVM_PPC_GET_SMMU_INFO ioctl Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 11/24] powerpc: Update tlbie/tlbiel as per ISA doc Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 12/24] powerpc: print both base and actual page size on hash failure Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 13/24] powerpc: Print page size info during boot Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 14/24] powerpc: Fix hpte_decode to use the correct decoding for page sizes Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 15/24] mm/THP: HPAGE_SHIFT is not a #define on some arch Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 16/24] mm/THP: Add pmd args to pgtable deposit and withdraw APIs Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 17/24] mm/THP: withdraw the pgtable after pmdp related operations Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 18/24] powerpc/THP: Implement transparent huge pages for ppc64 Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 19/24] powerpc/THP: Differentiate THP PMD entries from HUGETLB PMD entries Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 20/24] powerpc/THP: Add code to handle HPTE faults for large pages Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 21/24] powerpc: Handle huge page in perf callchain Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 22/24] powerpc/THP: hypervisor require few WIMG bit set Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 23/24] powerpc/THP: get_user_pages_fast changes Aneesh Kumar K.V
2013-02-26 8:05 ` [PATCH -V1 24/24] powerpc/THP: Enable THP on PPC64 Aneesh Kumar K.V
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