linux-kernel - Re: [RFC PATCH v19 0/8] mm: security: ro protection for dynamic data

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Message-ID: <fc984bf4-c46a-976c-ec74-ad89dc3d150e@huawei.com>
Date:   Thu, 15 Mar 2018 15:43:49 +0200
From:   Igor Stoppa <igor.stoppa@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <keescook@...omium.org>, <david@...morbit.com>,
        <rppt@...ux.vnet.ibm.com>, <mhocko@...nel.org>,
        <labbott@...hat.com>, <linux-security-module@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [RFC PATCH v19 0/8] mm: security: ro protection for dynamic data



On 14/03/2018 19:33, Matthew Wilcox wrote:
> On Wed, Mar 14, 2018 at 06:11:22PM +0200, Igor Stoppa wrote:

[...]

>> Probably page_frag does well with relatively large allocations, while
>> genalloc seems to be better for small (few allocation units) allocations.
> 
> I don't understand why you would think that.  If you allocate 4096 1-byte
> elements, page_frag will just use up a page.  Doing the same thing with
> genalloc requires allocating two bits per byte (1kB of bitmap), plus
> other overheads.

I had misunderstood the amount of page_frag structures needed.

--
igor