linux-kernel - 3.6-rc7 32-bit PAE miscalculates dirty page limits

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-next>] [day] [month] [year] [list]

Message-ID: <5068130A.4050602@pierre-beck.de>
Date:	Sun, 30 Sep 2012 11:38:45 +0200
From:	Pierre Beck <mail@...rre-beck.de>
To:	linux-kernel@...r.kernel.org
Subject: 3.6-rc7 32-bit PAE miscalculates dirty page limits

Hi,

there seems to be a bug in either ext4 or VM code triggered with 16 GB 
memory when compiled with 32-bit and PAE. dirty_background_ratio 
defaults to 10, dirty_ratio to 20. But in effect, dirty pages are 
strongly limited (zero or negative?). I observed extreme I/O wait states 
and slow disk access. A quick cure was to set dirty_bytes and 
dirty_background_bytes to sane values, overriding the ratios. An 
educated guess: the result of dirty_ratio calculation is stored as an 
unsigned 32-bit integer and overflows?

Greetings,

Pierre Beck
--
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/