linux-kernel - Re: [PATCH 2/2] mm: add overcommit

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: <5214E96B.3090009@intel.com>
Date:	Wed, 21 Aug 2013 09:23:07 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Jerome Marchand <jmarchan@...hat.com>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: add overcommit_kbytes sysctl variable

On 08/21/2013 08:22 AM, Jerome Marchand wrote:
>> > Instead of introducing yet another tunable, why don't we just make the
>> > ratio that comes in from the user more fine-grained?
>> > 
>> > 	sysctl overcommit_ratio=0.2
>> > 
>> > We change the internal 'sysctl_overcommit_ratio' to store tenths or
>> > hundreths of a percent (or whatever), then parse the input as two
>> > integers.  I don't think we need fully correct floating point parsing
>> > and rounding here, so it shouldn't be too much of a chore.  It'd
>> > probably end up being less code than you have as it stands.
>> > 
> Now that I think about it, that could break user space. Sure write access
> wouldn't be a problem (one can still write a plain integer), but a script
> that reads a fractional value when it expects an integer might not be able
> to cope with it.

You're right.  Something doing FOO=$(cat overcommit_ratio) and then
trying do do arithmetic would just fail loudly.  But, it would probably
fail silently if we create another tunable that all of a sudden returns
0 (when the kernel is not _behaving_ like it is set to 0).

I'm not sure there's a good way out of this without breakage (or at
least confusing) of _some_ old scripts/programs.  Either way has ups and
downs.

The existing dirty_ratio/bytes stuff just annoys me because I end up
having to check two places whenever I go looking for it.

--
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/