linux-kernel - Re: [RFC V2 12/12] mm: Tag VMA with VM_CDM flag explicitly during mbind(MPOL

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Message-ID: <26a17cd1-dd50-43b9-03b1-dd967466a273@intel.com>
Date:   Mon, 30 Jan 2017 09:54:27 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     mhocko@...e.com, vbabka@...e.cz, mgorman@...e.de,
        minchan@...nel.org, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, srikar@...ux.vnet.ibm.com,
        haren@...ux.vnet.ibm.com, jglisse@...hat.com,
        dan.j.williams@...el.com
Subject: Re: [RFC V2 12/12] mm: Tag VMA with VM_CDM flag explicitly during
 mbind(MPOL_BIND)

On 01/29/2017 07:35 PM, Anshuman Khandual wrote:
> +		if ((new_pol->mode == MPOL_BIND)
> +			&& nodemask_has_cdm(new_pol->v.nodes))
> +			set_vm_cdm(vma);

So, if you did:

	mbind(addr, PAGE_SIZE, MPOL_BIND, all_nodes, ...);
	mbind(addr, PAGE_SIZE, MPOL_BIND, one_non_cdm_node, ...);

You end up with a VMA that can never have KSM done on it, etc...  Even
though there's no good reason for it.  I guess /proc/$pid/smaps might be
able to help us figure out what was going on here, but that still seems
like an awful lot of damage.