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Re: [Qemu-devel] [PATCH] Add warmup phase for live migration of large me


From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH] Add warmup phase for live migration of large memory apps
Date: Thu, 12 May 2011 08:12:45 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10

On 05/12/2011 06:23 AM, Shribman, Aidan wrote:
From: Juan Quintela [mailto:address@hidden

If there are no additional dirty pages to be sent
i.e. ram_save_remaining() == 0 then the migration *will* converge
(even though we don't want it to) see:

This should be a really idle guest to have that O:-)

But if that is the whole problem, I would change the code to make the
case of max_downtime == 0 to mean that migration didn't converge.


I agree this would be fine as surrogate for the warmup patch as I proposed. New 
patch based on your's / Anthony's suggestion:

---
diff --git a/arch_init.c b/arch_init.c
index 4486925..9a35411 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -295,7 +295,8 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, 
void *opaque)

      expected_time = ram_save_remaining() * TARGET_PAGE_SIZE / bwidth;

-    return (stage == 2)&&  (expected_time<= migrate_max_downtime());
+    return (stage == 2)&&  migrate_max_downtime()&&
+        (expected_time<= migrate_max_downtime());
  }


This is better but let's make sure to document this behavior (and please include a Signed-off-by: in the next patch).

Regards,

Anthony Liguori

  static inline void *host_from_stream_offset(QEMUFile *f,
---

Best,
Aidan




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