[RFC PATCH] accel/tcg: change default codegen buffer size for i386-softmmu

[Alex Bennée]

There are two justifications for making this change. The first is that
i386 emulation is typically for smaller machines where having a 1gb of
generated code is overkill for basic emulation. The second is the
propensity of self-modifying code (c.f. Doom/edit) utilised on i386
systems can trigger a rapid growth in invalidated and re-translated
buffers. This is seen in bug #283. Execution is still inefficient but
at least the host memory isn't so aggressively used up.

That said it's still really just a sticking plaster for user
convenience.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Thomas Huth <thuth@redhat.com>
Cc: 1896298@bugs.launchpad.net
---
 accel/tcg/translate-all.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 640ff6e3e7..f442165674 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -951,9 +951,13 @@ static void page_lock_pair(PageDesc **ret_p1, 
tb_page_addr_t phys1,
  * Users running large scale system emulation may want to tweak their
  * runtime setup via the tb-size control on the command line.
  */
+#ifdef TARGET_I386
+#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (32 * MiB)
+#else
 #define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (1 * GiB)
 #endif
 #endif
+#endif
 
 #define DEFAULT_CODE_GEN_BUFFER_SIZE \
   (DEFAULT_CODE_GEN_BUFFER_SIZE_1 < MAX_CODE_GEN_BUFFER_SIZE \
-- 
2.20.1