linux-kernel - Re: [RFC 0/7] introduce memory hinting API for external process

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]

Message-ID: <20190521050144.GK10039@google.com>
Date:   Tue, 21 May 2019 14:01:44 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tim Murray <timmurray@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Daniel Colascione <dancol@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>
Subject: Re: [RFC 0/7] introduce memory hinting API for external process

On Mon, May 20, 2019 at 06:44:52PM -0700, Matthew Wilcox wrote:
> On Mon, May 20, 2019 at 12:52:47PM +0900, Minchan Kim wrote:
> > IMHO we should spell it out that this patchset complements MADV_WONTNEED
> > and MADV_FREE by adding non-destructive ways to gain some free memory
> > space. MADV_COLD is similar to MADV_WONTNEED in a way that it hints the
> > kernel that memory region is not currently needed and should be reclaimed
> > immediately; MADV_COOL is similar to MADV_FREE in a way that it hints the
> > kernel that memory region is not currently needed and should be reclaimed
> > when memory pressure rises.
> 
> Do we tear down page tables for these ranges?  That seems like a good

True for MADV_COLD(reclaiming) but false for MADV_COOL(deactivating) at
this implementation.

> way of reclaiming potentially a substantial amount of memory.

Given that consider refauting are spread out over time and reclaim occurs
in burst, that does make sense to speed up the reclaiming. However, a
concern to me is anonymous pages since they need swap cache insertion,
which would be wasteful if they are not reclaimed, finally.