linux-kernel - Re: [PATCH] x86: copy_oldmem_page using cached addressing

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]

Date:	Wed, 08 Sep 2010 21:42:18 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Cliff Wickman <public-cpw-sJ/iWh9BUns@...ne.gmane.org>
Cc:	public-kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@...ne.gmane.org,
	public-mingo-X9Un+BFzKDI@...ne.gmane.org,
	public-linux-kernel-u79uwXL29TY76Z2rM5mHXA@...ne.gmane.org
Subject: Re: [PATCH] x86: copy_oldmem_page using cached addressing



Cliff Wickman <cpw-sJ/iWh9BUns@...lic.gmane.org> writes:

> From: Cliff Wickman <cpw-sJ/iWh9BUns@...lic.gmane.org>
>
> The copy of /proc/vmcore to a user buffer proceeds much faster
> if the kernel addresses memory as cached.
>
> With this patch we have seen an increase in transfer rate from less than
> 15MB/s to 80-460MB/s, depending on size of the transfer.  This makes
> a big difference in time needed to save a system dump.
>
> (Does anyone know of a reason why copy_oldmem_page() would need
>  to use uncached addresses?)
>
> Diffed against 2.6.36-rc3

I had a similar patch somewhere in my private kernels,
yes it's a big win. I think it was simply a bug that was added
when ioremap was changed to default to uncached.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.

--
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/