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[Qemu-devel] Translation cache sizes

From: Julian Seward
Subject: [Qemu-devel] Translation cache sizes
Date: Sat, 8 Apr 2006 04:13:52 +0100
User-agent: KMail/1.8.2

Using qemu from cvs simulating x86-softmmu (no kqemu) on x86,
booting SuSE 9.1 and getting to the xdm (kdm?) graphical login
screen, requires making about 1088000 translations, and the
translation cache is flushed 17 times.  Booting is not too bad,
but once user-mode starts to run the translation cache is pretty
much hammered.

I made 2 changes: 

* increase CODE_GEN_BUFFER_SIZE from 16*1024*1024
  to 64*1024*1024, 

* observe that CODE_GEN_AVG_BLOCK_SIZE of 128
  for the softmmu case is too low; my measurements put it
  at about 247.  So I changed it to 256.

With those changes in place, the same boot-to-kdm process 
requires only about 570000 translations to be made, and 2 
cache flushes to happen.  Of course the cost is an extra
48M of memory use.


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