linux-kernel - Re: [PATCH v29 04/13] mm/idle_page_tracking: Make PG

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: <20210611134920.6302-1-sjpark@amazon.de>
Date:   Fri, 11 Jun 2021 13:49:20 +0000
From:   SeongJae Park <sj38.park@...il.com>
To:     "Shah, Amit" <aams@...zon.de>
Cc:     "sj38.park@...il.com" <sj38.park@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "snu@...zon.de" <snu@...zon.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "minchan@...nel.org" <minchan@...nel.org>,
        "vdavydov.dev@...il.com" <vdavydov.dev@...il.com>,
        "linux-damon@...zon.com" <linux-damon@...zon.com>,
        "zgf574564920@...il.com" <zgf574564920@...il.com>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "fan.du@...el.com" <fan.du@...el.com>,
        "Park, Seongjae" <sjpark@...zon.de>,
        "amit@...nel.org" <amit@...nel.org>,
        "gthelen@...gle.com" <gthelen@...gle.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "Foerster, Leonard" <foersleo@...zon.de>,
        "guoju.fgj@...baba-inc.com" <guoju.fgj@...baba-inc.com>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "shakeelb@...gle.com" <shakeelb@...gle.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        "greg@...ah.com" <greg@...ah.com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "mgorman@...e.de" <mgorman@...e.de>,
        "Jonathan.Cameron@...wei.com" <Jonathan.Cameron@...wei.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "brendanhiggins@...gle.com" <brendanhiggins@...gle.com>,
        "corbet@....net" <corbet@....net>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "elver@...gle.com" <elver@...gle.com>,
        "riel@...riel.com" <riel@...riel.com>, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v29 04/13] mm/idle_page_tracking: Make PG_idle reusable

From: SeongJae Park <sjpark@...zon.de>

Hi Amit,

On Fri, 11 Jun 2021 12:55:27 +0000 "Shah, Amit" <aams@...zon.de> wrote:

> On Thu, 2021-05-20 at 07:56 +0000, SeongJae Park wrote:
> > From: SeongJae Park <sjpark@...zon.de>
> > 
> > PG_idle and PG_young allow the two PTE Accessed bit users, Idle Page
> > Tracking and the reclaim logic concurrently work while don't interfere
> 
> ... while not interfering with ...

Will fix so.

> 
> > each other.  That is, when they need to clear the Accessed bit, they set
> > PG_young to represent the previous state of the bit, respectively.  And
> > when they need to read the bit, if the bit is cleared, they further read
> > the PG_young to know whether the other has cleared the bit meanwhile or
> > not.
> > 
> > We could add another page flag and extend the mechanism to use the flag
> > if we need to add another concurrent PTE Accessed bit user subsystem.
> > However, the space is limited.  Meanwhile, if the new subsystem is
> > mutually exclusive with IDLE_PAGE_TRACKING or interfering with it is not
> > a real problem, it would be ok to simply reuse the PG_idle flag.
> > However, it's impossible because the flags are dependent on
> > IDLE_PAGE_TRACKING.
> 
> For better readability, I suggest:
> 
> For yet another user of the PTE Accessed bit, we could add another page
> flag, or extend the mechanism to use the flags. For the DAMON usecase,
> however, we don't need to do that just yet.  IDLE_PAGE_TRACKING and
> DAMON are mutually exclusive, so there's only ever going to be one user
> of the current set of flags. 
> 
> In this commit, we split out the CONFIG options to allow for the use of
> PG_young and PG_idle outside of idle page tracking.

Thank you for the suggestion, it looks better to me, either.  I will update so
in the next spin.


Thanks,
SeongJae Park

[...]