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[Xen-devel] Possible bugs and doubts about readjusting weights/slice-len

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Possible bugs and doubts about readjusting weights/slice-lengths from command prompt
From: "Amitayu Das" <amitayudas@xxxxxxxxx>
Date: Wed, 3 May 2006 01:48:14 -0400
Cc: rhim@xxxxxxxxxxxxx
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I had few doubts/questions about readjusting slice/period length (or weights) for domains from command prompt. If someone can clarify, that'd be very nice. Here is the list (with respect to sedf scheduler):

1. Is is true that mentioning weights for a domain is setting a maximum limit for it so that it can't go beyond that limit by setting extra flag on? If that's the case, why in xen/common/scehd_sedf.c, a checking for extra flag is being made at first:

    if ( cmd->direction == SCHED_INFO_PUT )
        if (cmd->u.sedf.weight) {
            if ((cmd->u.sedf.extratime & EXTRA_AWARE) &&
                (! cmd->u.sedf.period)) {
                /*weight driven domains with xtime ONLY!*/

Please let me know if I'm missing something.

2. Say, I'm readjusting the slice lengths of running domains. While doing that, I make a mistake by having sum of the slice-lengths higher than period-length. In such cases, what does Xen actually do? I did not find sanity-checking code for such cases in xen/common/sched_sedf.c. Please let me know in case it's not there, why so or it's there, only I did not find it.

3. I tried to modify/readjust the slice/period length (or weights) for domains from command prompt.  However, I  found out that  changes are immaterial after first attempt. That is, no matter what changes I made at second or third or fourth time, they are not actually taking place. Only, the changes made during the first attempt actually took place. Please let me know if this is a bug in the existing code or I should have done the things in a different manner.

Thanks in advance,

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