linux-kernel - Re: [PATCH v1 00/16] ext4: Add metadata checksumming

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: <yq139gcymqj.fsf@sermon.lab.mkp.net>
Date:	Sun, 04 Sep 2011 18:19:16 -0400
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	djwong@...ibm.com, "Greg Freemyer" <greg.freemyer@...il.com>,
	"Andreas Dilger" <adilger.kernel@...ger.ca>,
	"Theodore Tso" <tytso@....edu>,
	"Sunil Mushran" <sunil.mushran@...cle.com>,
	"Amir Goldstein" <amir73il@...il.com>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"Mingming Cao" <cmm@...ibm.com>,
	"Joel Becker" <jlbec@...lplan.org>,
	"linux-fsdevel" <linux-fsdevel@...r.kernel.org>,
	linux-ext4@...r.kernel.org, "Coly Li" <colyli@...il.com>
Subject: Re: [PATCH v1 00/16] ext4: Add metadata checksumming

>>>>> "Andi" == Andi Kleen <andi@...stfloor.org> writes:

Andi> Doesn't have any performance numbers.

It's been a while since I read them. I thought they had some compelling
numbers. Anyway, made a big difference in real life testing here. For
sustained I/O we're talking an order of magnitude.

Andi> You need to keep in mind that PCLMULQDQ uses FPU state, so any
Andi> speedup for the kernel must be large enough to amortize the cost
Andi> of saving the FPU state.

Yeah, my test cases were for bulk database I/O, not for writing a
handful of fs metadata blocks. Plus for the DB tests the CRC was
generated in userland.

I seem to recall Joel picking something other than the hw-accelerated
CRC32C for ocfs2 metadata and that didn't cause any problems.

That said, I do see a difference between IP checksum and CRC on normal
FS workloads with DIX enabled here.

Andi> Typically that only works out for quite large buffers, but kernel
Andi> buffers are relatively small.

*nod*

-- 
Martin K. Petersen	Oracle Linux Engineering
--
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/