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: <877hgmr72o.fsf@gmail.com>
Date:	Tue, 09 Nov 2010 07:54:07 -0500
From:	Ben Gamari <bgamari.foss@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-kernel@...r.kernel.org,
	rsync@...ts.samba.org, linux-mm@...ck.org
Subject: Re: fadvise DONTNEED implementation (or lack thereof)

On Tue,  9 Nov 2010 16:28:02 +0900 (JST), KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> So, I don't think application developers will use fadvise() aggressively
> because we don't have a cross platform agreement of a fadvice behavior.
> 
I strongly disagree. For a long time I have been trying to resolve
interactivity issues caused by my rsync-based backup script. Many kernel
developers have said that there is nothing the kernel can do without
more information from user-space (e.g. cgroups, madvise). While cgroups
help, the fix is round-about at best and requires configuration where
really none should be necessary. The easiest solution for everyone
involved would be for rsync to use FADV_DONTNEED. The behavior doesn't
need to be perfectly consistent between platforms for the flag to be
useful so long as each implementation does something sane to help
use-once access patterns.

People seem to mention frequently that there are no users of
FADV_DONTNEED and therefore we don't need to implement it. It seems like
this is ignoring an obvious catch-22. Currently rsync has no fadvise
support at all, since using[1] the implemented hints to get the desired
effect is far too complicated^M^M^M^Mhacky to be considered
merge-worthy. Considering the number of Google hits returned for
fadvise, I wouldn't be surprised if there were countless other projects
with this same difficulty. We want to be able to tell the kernel about
our useage patterns, but the kernel won't listen.

Cheers,

- Ben

[1] http://insights.oetiker.ch/linux/fadvise.html
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ