We are seeig the same behavior on FC and IB where we cannot exceed 512K IO size on RHEL 5.1. We even tried increasing the max_sectors_kb and the max_hw_sectors_kb To 4096 For each device: echo 4096 > /sys/block/<device>/queue/max_hw_sectors_kb echo 4096 > /sys/block/<device>/queue/max_sectors_kb But still the same 512K. I've noticed that the file /usr/src/kernels/2.6.18-53.el5-x86_64/include/linux/blkdev.h has the BLK_DEF_MAX_SECTORS set to 1024 sectors (512K IO size). #define MAX_PHYS_SEGMENTS 128 #define MAX_HW_SEGMENTS 128 #define SAFE_MAX_SECTORS 255 #define BLK_DEF_MAX_SECTORS 1024 Is there a way to increase it either dynamically or through a patch? BTW, on RHEL 4.5 I didn't see such limit: #define MAX_PHYS_SEGMENTS 128 #define MAX_HW_SEGMENTS 128 #define MAX_SECTORS 255 This could explain why we could run more than 512K IOs on RHEL 4.5
Thanks. Abdel.. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Pasi Kärkkäinen Sent: Thursday, May 15, 2008 7:36 AM To: Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list Subject: Re: [rhelv5-list] MAX IO SIZE On Wed, May 14, 2008 at 07:40:16PM +0300, Pasi Kärkkäinen wrote: > On Wed, May 14, 2008 at 09:09:30AM -0600, Sadek, Abdel wrote: > > I was able to run more than 1 MB IOs on RHEL 4.5 (I believe I ran up to 2 > > MB so far). > > > > OK. You might want to ask about this on linux-scsi or linux-kernel > mailinglist.. > Did you figure out anything? -- Pasi _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list
