linux-kernel - Re: [RFC][PATCH 0/5] VM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 27 May 2014 00:49:08 +0400
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Mike Marciniszyn <infinipath@...el.com>
Subject: Re: [RFC][PATCH 0/5] VM_PINNED

On Tue, May 27, 2014 at 12:32 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, May 27, 2014 at 12:19:16AM +0400, Konstantin Khlebnikov wrote:
>> On Mon, May 26, 2014 at 6:56 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> > Hi all,
>> >
>> > I mentioned at LSF/MM that I wanted to revive this, and at the time there were
>> > no disagreements.
>> >
>> > I finally got around to refreshing the patch(es) so here goes.
>> >
>> > These patches introduce VM_PINNED infrastructure, vma tracking of persistent
>> > 'pinned' page ranges. Pinned is anything that has a fixed phys address (as
>> > required for say IO DMA engines) and thus cannot use the weaker VM_LOCKED. One
>> > popular way to pin pages is through get_user_pages() but that not nessecarily
>> > the only way.
>>
>> Lol, this looks like resurrection of VM_RESERVED which I've removed
>> not so long time ago.

That was swap-out prevention from 2.4 era, something between VM_IO and
VM_LOCKED with various side effects.

>
> Not sure what VM_RESERVED did, but there might be a similarity.
>
>> Maybe single-bit state isn't flexible enought?
>
> Not sure what you mean, the one bit is perfectly fine for what I want it
> to do.
>
>> This supposed to supports pinning only by one user and only in its own mm?
>
> Pretty much, that's adequate for all users I'm aware of and mirrors the
> mlock semantics.

Ok, fine. Because get_user_pages is used sometimes for pinning pages
from different mm.

Another suggestion. VM_RESERVED is stronger than VM_LOCKED and extends
its functionality.
Maybe it's easier to add VM_DONTMIGRATE and use it together with VM_LOCKED.
This will make accounting easier. No?

>
>> This might be done as extension of existing memory-policy engine.
>> It allows to keep vm_area_struct slim in normal cases and change
>> behaviour when needed.
>> memory-policy might hold reference-counter of "pinners", track
>> ownership and so on.
>
> That all sounds like raping the mempolicy code and massive over
> engineering.
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/