linux-kernel - Re: [RFC][PATCH 4/5] memory_pressure

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: <cfd9edbf0801151455j48669850s7ea4fe589dbb9710@mail.gmail.com>
Date:	Tue, 15 Jan 2008 23:55:17 +0100
From:	"Daniel Spång" <daniel.spang@...il.com>
To:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"Marcelo Tosatti" <marcelo@...ck.org>,
	"Rik van Riel" <riel@...hat.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH 4/5] memory_pressure_notify() caller

Hi,

On 1/15/08, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> the notification point to happen whenever the VM moves an
> anonymous page to the inactive list - this is a pretty good indication
> that there are unused anonymous pages present which will be very likely
> swapped out soon.

> +                               /* deal with the case where there is no
> +                                * swap but an anonymous page would be
> +                                * moved to the inactive list.
> +                                */
> +                               if (!total_swap_pages && reclaim_mapped &&
> +                                   PageAnon(page))
> +                                       inactivated_anon = 1;

As you know I have had some concerns regarding a too early
notification in a swapless system.

I did a test with a populated page cache in a swapless system:

$ cat /bigfile > /dev/null # populate page cache
$ cat /proc/meminfo
MemTotal:      1037040 kB
MemFree:        113976 kB
Buffers:          1068 kB
Cached:         907552 kB
SwapCached:          0 kB
Active:          11116 kB
Inactive:       903968 kB
HighTotal:      130992 kB
HighFree:          252 kB
LowTotal:       906048 kB
LowFree:        113724 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:              36 kB
Writeback:           0 kB
AnonPages:        6484 kB
Mapped:           1216 kB
Slab:             4024 kB
SReclaimable:      864 kB
SUnreclaim:       3160 kB
PageTables:        444 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:    518520 kB
Committed_AS:    18816 kB
VmallocTotal:   114680 kB
VmallocUsed:       904 kB
VmallocChunk:   113672 kB

Start to allocate memory, 10 MB every second, exit on notification.

$ cat /proc/meminfo # just after notification
MemTotal:      1037040 kB
MemFree:        123468 kB
Buffers:           876 kB
Cached:         897976 kB
SwapCached:          0 kB
Active:          12984 kB
Inactive:       892332 kB
HighTotal:      130992 kB
HighFree:         1064 kB
LowTotal:       906048 kB
LowFree:        122404 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:               0 kB
Writeback:           0 kB
AnonPages:        6484 kB
Mapped:           1220 kB
Slab:             4012 kB
SReclaimable:      864 kB
SUnreclaim:       3148 kB
PageTables:        448 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:    518520 kB
Committed_AS:    18816 kB
VmallocTotal:   114680 kB
VmallocUsed:       904 kB
VmallocChunk:   113672 kB

The notification fires after only ~100 MB allocated, i.e., when page
reclaim is beginning to nag from page cache. Isn't this a bit early?
Repeating the test with swap enabled results in a notification after
~600 MB allocated, which is more reasonable and just before the system
starts to swap.

Cheers,
Daniel
--
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/