virtio

Posted on 2025-02-10 Edited on 2025-05-30 In utilities Views: Disqus:

virtio - 半虚拟化设备标准

对比项	全虚拟化（Emulated）	Virtio（半虚拟化）	SR-IOV（直通）
性能	❌ 低（模拟开销大）	✅ 高	✅✅ 超高（硬件直通）
驱动支持	无需额外驱动（但慢）	需要Virtio 驱动	需要物理设备驱动
适用场景	适用于无 Virtio 支持的旧 OS	普遍适用于 VM	适用于高性能网络存储
硬件需求	无特殊需求	无特殊需求	需要硬件支持

Piglit

Posted on 2025-02-07 Edited on 2025-05-30 In graphics Views: Disqus:

flowchart TB
  subgraph p [Main Thread]
    subgraph p0 ["piglit_drm_create_dma_buf()"]
      p.a["drv->create(w, h, fourcc, src_data, drm_buf)"]
      p.b["drv->export(drm_buf)"]
      subgraph p1 ["create_and_destroy_texture()"]
        p.c["egl_image_for_dma_buf_fd<br>(buf, fd, fourcc, img)"]
        p.d["texture_for_egl_image(img, texture)"]
        p.e["eglDestroyImageKHR(display, img)"]
        p.f["glDeleteTextures(1, &texture)"]
        p.g["glFinish()"]
      end
    end
  end
  subgraph t1 [Thread 1]
    subgraph lo11 [Loop 1]
      t1.a["eglCreateContext()"]
      t1.b["eglMakeCurrent()"]
      subgraph lo111 ["create_and_destroy_texture()"]
        t1.c["egl_image_for_dma_buf_fd<br>(buf, fd, fourcc, img)"]
        t1.d["texture_for_egl_image(img, texture)"]
        t1.e["eglDestroyImageKHR(display, img)"]
        t1.f["glDeleteTextures(1, &texture)"]
        t1.g["glFinish()"]
      end
    end
  end

  subgraph t2 [Thread 2]
    subgraph lo21 [Loop 1]
      t2.a["eglCreateContext()"]
      t2.b["eglMakeCurrent()"]
      subgraph lo211 ["create_and_destroy_texture()"]
        t2.c["egl_image_for_dma_buf_fd<br>(buf, fd, fourcc, img)"]
        t2.d["texture_for_egl_image(img, texture)"]
        t2.e["eglDestroyImageKHR(display, img)"]
        t2.f["glDeleteTextures(1, &texture)"]
        t2.g["glFinish()"]
      end
    end
  end

  p.a --> p.b --> p.c --> p.d --> p.e --> p.f --> p.g

  t1.a --> t1.b --> t1.c --> t1.d --> t1.e --> t1.f --> t1.g
  t2.a --> t2.b --> t2.c --> t2.d --> t2.e --> t2.f --> t2.g

  p --> t1
  p --> t2

  lo11 -- 100000 times --> lo11
  lo21 -- 100000 times --> lo21

  click p.a https://gitlab.freedesktop.org/mesa/piglit/-/blob/main/tests/util/piglit-framework-gl/piglit_drm_dma_buf.c#L519"
  click p.b https://gitlab.freedesktop.org/mesa/piglit/-/blob/main/tests/util/piglit-framework-gl/piglit_drm_dma_buf.c#L519"

strace - System Call Tracing

Posted on 2025-01-14 Edited on 2025-05-30 In linux Views: Disqus:

strace -c -w -o glmark2.strace glmark2

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ------------------
 55.82   14.421660          55    258416           ioctl
 16.68    4.309981          18    238578    205238 recvmsg
 14.62    3.777039          17    210879        42 futex
  5.06    1.306534          16     77652           getpid
  2.73    0.705886          21     33276           writev
  2.51    0.648318          17     36385           close
  2.40    0.620114          18     33335           ppoll
  0.04    0.011076          24       452           read
  0.04    0.009150          32       281        47 openat
  0.02    0.005639          30       187           mmap
  0.01    0.003267          28       113           munmap
  0.01    0.003240          21       152       120 readlinkat
  0.01    0.002085          26        80           mprotect
  0.01    0.002033          19       104           newfstatat
  0.01    0.001976          26        75           brk
  0.01    0.001364          71        19           recvfrom
  0.00    0.001138          54        21           clone3
  0.00    0.000778          18        43           rt_sigprocmask
  0.00    0.000679          27        25           write
  0.00    0.000645          29        22           getdents64
  0.00    0.000493         492         1           execve
  0.00    0.000323          17        18           lseek
  0.00    0.000249          20        12           getrusage
  0.00    0.000232          17        13           getrandom
  0.00    0.000163          27         6           memfd_create
  0.00    0.000150          24         6           sendmsg
  0.00    0.000136          22         6           ftruncate
  0.00    0.000131          16         8           fcntl
  0.00    0.000054          18         3           geteuid
  0.00    0.000054          18         3           getuid
  0.00    0.000047          23         2         1 faccessat
  0.00    0.000037          18         2           uname
  0.00    0.000033          32         1           socket
  0.00    0.000031          30         1           shutdown
  0.00    0.000028          27         1           connect
  0.00    0.000018          17         1           getpeername
  0.00    0.000018          17         1           sched_getaffinity
  0.00    0.000017          17         1           rt_sigaction
  0.00    0.000017          16         1           prlimit64
  0.00    0.000017          16         1           set_tid_address
  0.00    0.000016          16         1           rseq
  0.00    0.000016          16         1           set_robust_list
------ ----------- ----------- --------- --------- ------------------
100.00   25.834885          29    890185    205448 total

Render To Texture

Posted on 2025-01-11 Edited on 2025-05-30 In graphics Views: Disqus:

Render-To-Texture 是一种十分常见和简单的渲染技术，它将纹理对象和 FBO 绑定，把场景渲染到纹理中，以便之后可以反复使用。RTT 被广泛应用在 in-game cameras(virtual camera systems), post-processing 和各种特效中。本文主要比较 RTT 技术在两种不同的渲染架构下的不同和一些思考。

rtt-on-tbr