linux-kernel - Re: [PATCH 8/8] Per-container pages reclamation

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:	Fri, 01 Jun 2007 11:44:25 +0400
From:	Pavel Emelianov <xemul@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Balbir Singh <balbir@...ibm.com>, Paul Menage <menage@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org, Kirill Korotaev <dev@...nvz.org>
Subject: Re: [PATCH 8/8] Per-container pages reclamation

Andrew Morton wrote:
> On Thu, 31 May 2007 14:35:43 +0400
> Pavel Emelianov <xemul@...nvz.org> wrote:
> 
>>> Would I be correct in guessing that pages which are on the
>>> per-rss-container lists are also eligible for reclaim off the traditional
>>> page LRUs?  If so, how does that work?  When a page gets freed off the
>> Yes. All the pages are accessible from booth - global and per-container
>> LRU lists and reclamation can be performed from booth.
>>
>>> per-zone LRUs does it also get removed from the per-rss_container LRU?  But
>>> how can this be right?  
>> I don't get your idea here.
> 
> If we have a page which is on the zone LRU with refcount=1 and someone does
> put_page() on it, we will take that page off the zone LRU and then actually
> free the page.
> 
> I am assuming that your patches change that logic so that we will also
> remove that page from the per-container LRU at the same time?

Oh, I see. No that will work another way. Page stays in per-container
LRU lists as long as it is mapped. When the last process is unmapping
the page, it it is removed, but stays in global LRU till its refcount
drops to 0.

Since all unmaps happen from process-context this looks to be safe.

> If so, the problem which I see is that, under rare circumstances, that
> final put_page() will occur from interrupt context.  Hence we would be
> trying to remove the page from the per-container LRU at interrupt time. 
> But the locks which you have in there are not suited for taking from
> interrupt context.
> 
> 

Thanks,
Pavel.
-
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/