Re: kvm userspace: ksm support

[Izik Eidus]

Anthony Liguori wrote:
Izik Eidus wrote:
This patch is not for inclusion just rfc.
  

The madvise() interface looks really nice :-)
Thanks.


From 1297b86aa257100b3d819df9f9f0932bf4f7f49d Mon Sep 17 00:00:00 2001
From: Izik Eidus <iei...@redhat.com>
Date: Tue, 28 Jul 2009 19:14:26 +0300
Subject: [PATCH] kvm userspace: ksm support

rfc for ksm support to kvm userpsace.

thanks

Signed-off-by: Izik Eidus <iei...@redhat.com>
---
 exec.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/exec.c b/exec.c
index f6d9ec9..375cc18 100644
--- a/exec.c
+++ b/exec.c
@@ -2595,6 +2595,9 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
     new_block->host = file_ram_alloc(size, mem_path);
     if (!new_block->host) {
         new_block->host = qemu_vmalloc(size);
+#ifdef MADV_MERGEABLE
+        madvise(new_block->host, size, MADV_MERGEABLE);
+#endif
  

Are madvise calls additive?

Do we need to change the madvise balloon calls to include 
MADV_MERGEABLE or will this carry the property forever?

You mean: when we later call for other madvise calls, if it will remove 
the MADV_MERGEABLE from that memory?
if yes, the answer is no, it should be still l left in the vma->vm_flags...


I'd suggest doing the following in osdep.h too:

#if !defined(MADV_MERGABLE)
#define MADV_MERGABLE MADV_NORMAL
#endif

To avoid #ifdefs in .c files.

I tried to follow the way DONTFORK madvise is working...

So you say, just to throw this thing into osdep.h instead of that c file?


Regards,

Anthony Liguori

     }
     new_block->offset = last_ram_offset;
     new_block->length = size;
  


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