linux-kernel - Lower HD transfer rate with NCQ enabled?

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: <BAY20-F50719E454DCCF2309DA1AF9670@phx.gbl>
Date:	Tue, 03 Apr 2007 07:11:28 +0000
From:	"Paa Paa" <paapaa125@...mail.com>
To:	linux-kernel@...r.kernel.org
Subject: Lower HD transfer rate with NCQ enabled?

I'm using Linux 2.6.20.4. I noticed that I get lower SATA hard drive 
throughput with 2.6.20.4 than with 2.6.19. The reason was that 2.6.20 
enables NCQ by defauly (queue_depth = 31/32 instead of 0/32). Transfer rate 
was measured using "hdparm -t":

With NCQ (queue_depth == 31): 50MB/s.
Without NCQ (queue_depth == 0): 60MB/s.

20% difference is quite a lot. This is with Intel ICH8R controller and 
Western Digital WD1600YS hard disk in AHCI mode. I also used the next 
command to cat-copy a biggish (540MB) file and time it:

rm temp && sync && time sh -c 'cat quite_big_file > temp && sync'

Here I noticed no differences at all with and without NCQ. The times (real 
time) were basically the same in many successive runs. Around 19s.

Q: What conclusion can I make on "hdparm -t" results or can I make any 
conclusions? Do I really have lower performance with NCQ or not? If I do, is 
this because of my HD or because of kernel?

Best regards,
Paapaa

_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today it's FREE! 
http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/

-
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/