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[Xen-devel] Issues while running Xen with new RR scheduler

To: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Issues while running Xen with new RR scheduler
From: Ananth <cbananth@xxxxxxxxx>
Date: Tue, 28 Apr 2009 00:09:19 +0530
Cc: dunlapg@xxxxxxxxx
Delivery-date: Mon, 27 Apr 2009 11:41:01 -0700
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In continuation with my previous post, I am able to login to the compiled Xen. But it is continuing to run on credit scheduler even if i modify the kernel parameters to run using round robin scheduler.
I have pasted the contents of the /boot/grub/menu.lst file.

title Xen -- openSUSE 11.0 - manually compiled AGAIN
root (hd0,4)
kernel /boot/xen.gz
module /boot/vmlinuz- root=/dev/disk/by-id/scsi-SATA_Hitachi_HTS5416_SB2D04E4CE7YEE-part5 showopts sched=rrobin vga=0x314
module /boot/initrd-2.6.18-xen0

Incidentally, even if i give sched=sedf, it still runs only on credit scheduler. Please let me know your feedback on this issue. My aim is to study the performance statistics of credit, sedf and new RR scheduler. It would be great if you could give me any pointers to measure scheduler performance or get statistics from the system.

Thanks & Regards

---------- Forwarded message ----------
From: Ananth <cbananth@xxxxxxxxx>
Date: Mon, Apr 27, 2009 at 6:45 PM
Subject: Re: [Xen-devel] Fwd: Error while compiling with new RR scheduler
To: George Dunlap <dunlapg@xxxxxxxxx>
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>

Thank you so much for pointing it out. How could I miss something so obvious. I am able to compile it now. I will get back to you in case I get into any issues during run time.

Thank you.


On Mon, Apr 27, 2009 at 6:29 PM, George Dunlap <dunlapg@xxxxxxxxx> wrote:
The message says it pretty clearly:  you return the value of ret, but
there are control paths in the function for which ret.task is not set.
 Namely, if list_empty(runq) is true, then you will return an
uninitialized value, which may be anything (garbage on the stack,
NULL, &c).  This will most likely cause Xen to crash, as
xen/common/schedule.c assumes that ret.task will be a valid, non-NULL

If you happen to know that runq is never empty, then you don't need
the if statement.  If it may be empty, then you need an else clause to
return the idle vcpu for that processor.


2009/4/24 Ananth <cbananth@xxxxxxxxx>:
> Hi,
> I figured out that the error was because of a missing ' ; ' . This has been fixed now. I have attached the modified code.
> While compiling I am getting the below error message.
> cc1: warnings being treated as errors
> sched_rrobin.c: In function ‘rrobin_schedule’:
> sched_rrobin.c:74: error: ‘ret.task’ may be used uninitialized in this function
> Please guide.
> Thanks & Regards
> Ananth
> ---------- Forwarded message ----------
> From: Ananth <cbananth@xxxxxxxxx>
> Date: Fri, Apr 24, 2009 at 7:25 PM
> Subject: Error while compiling with new RR scheduler
> To: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
> Hi,
> Please find attached the source code of Round Robin scheduler which I am trying to add to Xen 3.3.1.
> I am facing the following error messages while compiling the same.
> sched_rrobin.c:31: error: two or more data types in declaration specifiers
> sched_rrobin.c: In function ‘rrobin_vcpu_init’:
> sched_rrobin.c:34: error: incompatible types in return
> sched_rrobin.c:51: error: incompatible types in return
> sched_rrobin.c:94: error: initialization from incompatible pointer type
> I believe the error in line 94 is causing the rest of the error messages. I have checked with the structure definition in sched-if.h as well as the implementation of the same in other schedulers such as SEDF and Credit.
> Request you to kindly provide your feedback regarding the same.
> Thanks & Regards
> Ananth
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