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From: "Alex Bennée" <1896298@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1896298] [RFC PATCH] accel/tcg: change default codegen buffer size for i386-softmmu
Date: Tue, 25 May 2021 16:45:41 -0000	[thread overview]
Message-ID: <20210525164541.17985-1-alex.bennee@linaro.org> (raw)
In-Reply-To: 160046874518.13612.4861858859499751315.malonedeb@gac.canonical.com

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

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1896298

Title:
  TCG memory leak with FreeDOS 'edit'

Status in QEMU:
  Expired

Bug description:
  qemu trunk as of today leaks memory FAST when freedos' edit is
  running.

  To reproduce, download:

  https://www.ibiblio.org/pub/micro/pc-
  stuff/freedos/files/repositories/1.3/cdrom.iso

  Then run:

  $ qemu-system-i386 -cdrom cdrom.iso

  select your language then select "return to DOS", then type

  > edit

  it will consume memory at ~10MB/s

  This does NOT happen when adding -enable-kvm

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1896298/+subscriptions


WARNING: multiple messages have this Message-ID (diff)
From: "Alex Bennée" <alex.bennee@linaro.org>
To: qemu-devel@nongnu.org
Cc: "Richard Henderson" <richard.henderson@linaro.org>,
	"Thomas Huth" <thuth@redhat.com>,
	1896298@bugs.launchpad.net,
	"Alex Bennée" <alex.bennee@linaro.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>
Subject: [RFC PATCH] accel/tcg: change default codegen buffer size for i386-softmmu
Date: Tue, 25 May 2021 17:45:41 +0100	[thread overview]
Message-ID: <20210525164541.17985-1-alex.bennee@linaro.org> (raw)
Message-ID: <20210525164541.kazTlnJ4DdwXdSBGBgHgsdaySA6Hz2t8pnQMo26UDcY@z> (raw)

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



  parent reply	other threads:[~2021-05-25 17:03 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-18 22:39 [Bug 1896298] [NEW] memory leak Michael Slade
2020-09-18 23:20 ` [Bug 1896298] " Michael Slade
2020-12-02  7:55 ` Thomas Huth
2021-05-11 13:35 ` Thomas Huth
2021-05-13 12:16 ` [Bug 1896298] Re: TCG memory leak with FreeDOS 'edit' Thomas Huth
2021-05-25 14:51 ` Alex Bennée
2021-05-25 16:45 ` Alex Bennée [this message]
2021-05-25 16:45   ` [RFC PATCH] accel/tcg: change default codegen buffer size for i386-softmmu Alex Bennée
2021-06-03 16:33   ` Alex Bennée
2021-06-03 16:33     ` [Bug 1896298] " Alex Bennée
2021-06-03 19:04   ` Richard Henderson
2021-06-04  7:42     ` Alex Bennée
2021-06-04  7:42       ` [Bug 1896298] " Alex Bennée

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