[Qemu-devel] [Bug 1618122] Re: qemu-monitor screendump very slow

[vans163 <vans_163@yahoo.com>]

** Description changed:

  qemu-monitor screendump often using 10-20% cpu usage of one core to take
  a small capture.
  
  Most of the CPU usage seems to come from libpixman. There were many
  reports of libpixman becoming 8 times slower in newer releases.
  
  https://github.com/qemu/qemu/blob/0c56c6ab68902281094c7aac6305e2321c34c187/ui/console.c#L285
  
  Simple Valgrind Ir report.
  
  --------------------------------------------------------------------------------
-             Ir
+            Ir 
  --------------------------------------------------------------------------------
- 56,592,286,124  PROGRAM TOTALS
+ 9,994,313,959  PROGRAM TOTALS
  
  --------------------------------------------------------------------------------
-             Ir  file:function
+            Ir  file:function
  --------------------------------------------------------------------------------
- 40,288,379,712  ???:0x000000000000caa0 [/usr/lib64/libpixman-1.so.0.34.0]
-  3,585,795,168  ???:0x000000000006df20 [/usr/lib64/libpixman-1.so.0.34.0]
-  1,763,982,432  ???:0x0000000000052360 [/usr/lib64/libpixman-1.so.0.34.0]
-  1,517,832,033  ???:__memcpy_sse2_unaligned [/usr/lib64/libc-2.23.so]
-    993,997,885  ???:__GI_mempcpy [/usr/lib64/libc-2.23.so]
-    484,059,456  ???:0x0000000000050430 [/usr/lib64/libpixman-1.so.0.34.0]
-    460,109,168  ???:pixman_image_composite32 [/usr/lib64/libpixman-1.so.0.34.0]
+ 4,883,603,360  /usr/src/debug/pixman-0.34.0/pixman/pixman-access.c:store_scanline_b8g8r8 [/usr/lib64/libpixman-1.so.0.34.0]
+   282,312,800  /usr/src/debug/pixman-0.34.0/pixman/pixman-implementation.c:_pixman_implementation_iter_init [/usr/lib64/libpixman-1.so.0.34.0]
+   267,394,160  /usr/src/debug/pixman-0.34.0/pixman/pixman-sse2.c:sse2_fetch_x8r8g8b8 [/usr/lib64/libpixman-1.so.0.34.0]
+   256,761,600  /usr/src/debug/pixman-0.34.0/pixman/pixman-private.h:store_scanline_b8g8r8
+   254,676,199  ???:0x0000000000011f40 [/usr/lib64/libjemalloc.so.2]
+   199,990,526  ???:0x0000000000011a10 [/usr/lib64/libjemalloc.so.2]
  
- I tried taking a look on how to fix this, but it seems pixman is deeply
- enrooted inside the monitor.  I wanted to try to simply take whats on
- the display and memcpy it into .ppm format manually creating the file
- header, but I cant figure out where the raw display buffer/image is
- gotten from.
+ 
+ I tried taking a look on how to fix this, but it seems pixman is deeply enrooted inside the monitor.  I wanted to try to simply take whats on the display and memcpy it into .ppm format manually creating the file header, but I cant figure out where the raw display buffer/image is gotten from.
  
  For example this is DisplaySurface:
  
  struct DisplaySurface {
      pixman_format_code_t format;
      pixman_image_t *image;
      uint8_t flags;
  #ifdef CONFIG_OPENGL
      GLenum glformat;
      GLenum gltype;
      GLuint texture;
  #endif
  };
  
  Which as you can see already has the pixman_image_t. Maybe I should just
  work with that pixman_image_t?
  
  The most effective solution IMO seems to just memcpy from the display
  into a premade header for a .ppm or .bmp file assuming 24 or 32 bpp. No
  need for libpixman.

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https://bugs.launchpad.net/bugs/1618122

Title:
  qemu-monitor screendump very slow

Status in QEMU:
  New

Bug description:
  qemu-monitor screendump often using 10-20% cpu usage of one core to
  take a small capture.

  Most of the CPU usage seems to come from libpixman. There were many
  reports of libpixman becoming 8 times slower in newer releases.

  https://github.com/qemu/qemu/blob/0c56c6ab68902281094c7aac6305e2321c34c187/ui/console.c#L285

  Simple Valgrind Ir report.

  --------------------------------------------------------------------------------
             Ir 
  --------------------------------------------------------------------------------
  9,994,313,959  PROGRAM TOTALS

  --------------------------------------------------------------------------------
             Ir  file:function
  --------------------------------------------------------------------------------
  4,883,603,360  /usr/src/debug/pixman-0.34.0/pixman/pixman-access.c:store_scanline_b8g8r8 [/usr/lib64/libpixman-1.so.0.34.0]
    282,312,800  /usr/src/debug/pixman-0.34.0/pixman/pixman-implementation.c:_pixman_implementation_iter_init [/usr/lib64/libpixman-1.so.0.34.0]
    267,394,160  /usr/src/debug/pixman-0.34.0/pixman/pixman-sse2.c:sse2_fetch_x8r8g8b8 [/usr/lib64/libpixman-1.so.0.34.0]
    256,761,600  /usr/src/debug/pixman-0.34.0/pixman/pixman-private.h:store_scanline_b8g8r8
    254,676,199  ???:0x0000000000011f40 [/usr/lib64/libjemalloc.so.2]
    199,990,526  ???:0x0000000000011a10 [/usr/lib64/libjemalloc.so.2]

  
  I tried taking a look on how to fix this, but it seems pixman is deeply enrooted inside the monitor.  I wanted to try to simply take whats on the display and memcpy it into .ppm format manually creating the file header, but I cant figure out where the raw display buffer/image is gotten from.

  For example this is DisplaySurface:

  struct DisplaySurface {
      pixman_format_code_t format;
      pixman_image_t *image;
      uint8_t flags;
  #ifdef CONFIG_OPENGL
      GLenum glformat;
      GLenum gltype;
      GLuint texture;
  #endif
  };

  Which as you can see already has the pixman_image_t. Maybe I should
  just work with that pixman_image_t?

  The most effective solution IMO seems to just memcpy from the display
  into a premade header for a .ppm or .bmp file assuming 24 or 32 bpp.
  No need for libpixman.

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