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authorKirill Smelkov <kirr@mns.spb.ru>2012-11-02 09:10:30 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2012-12-21 18:25:21 -0200
commite3a8b4d22b47b3ee17baccdc5b351465f890671c (patch)
treefabb3426239a407b21b2c945be39cc5c08ab8143 /drivers/media/platform
parent011b2aad587a770e758711f465312ac843440d2a (diff)
[media] vivi: Optimize gen_text()
I've noticed that vivi takes a lot of CPU to produce its frames. For example for 8 devices and 8 simple programs running, where each captures YUY2 640x480 and displays it to X via SDL, profile timing is as follows: # cmdline : /home/kirr/local/perf/bin/perf record -g -a sleep 20 # Samples: 82K of event 'cycles' # Event count (approx.): 31551930117 # # Overhead Command Shared Object Symbol # ........ ............... .................... # 49.48% vivi-* [vivi] [k] gen_twopix 10.79% vivi-* [kernel.kallsyms] [k] memcpy 10.02% rawv libc-2.13.so [.] __memcpy_ssse3 8.35% vivi-* [vivi] [k] gen_text.constprop.6 5.06% Xorg [unknown] [.] 0xa73015f8 2.32% rawv [vivi] [k] gen_twopix 1.22% rawv [vivi] [k] precalculate_line 1.20% vivi-* [vivi] [k] vivi_fillbuff (rawv is display program, vivi-* is a combination of vivi-000 through vivi-007) so a lot of time is spent in gen_twopix() which as the follwing call-graph profile shows ... 49.48% vivi-* [vivi] [k] gen_twopix | --- gen_twopix | |--96.30%-- gen_text.constprop.6 | vivi_fillbuff | vivi_thread | kthread | ret_from_kernel_thread | --3.70%-- vivi_fillbuff vivi_thread kthread ret_from_kernel_thread ... is called mostly from gen_text(). If we'll look at gen_text(), in the inner loop, we'll see if (chr & (1 << (7 - i))) gen_twopix(dev, pos + j * dev->pixelsize, WHITE, (x+y) & 1); else gen_twopix(dev, pos + j * dev->pixelsize, TEXT_BLACK, (x+y) & 1); which calls gen_twopix() for every character pixel, and that is very expensive, because gen_twopix() branches several times. Now, let's note, that we operate on only two colors - WHITE and TEXT_BLACK, and that pixel for that colors could be precomputed and gen_twopix() moved out of the inner loop. Also note, that for black and white colors even/odd does not make a difference for all supported pixel formats, so we could stop doing that `odd` gen_twopix() parameter game. So the first thing we are doing here is 1) moving gen_twopix() calls out of gen_text() into vivi_fillbuff(), to pregenerate black and white colors, just before printing starts. what we have next is that gen_text's font rendering loop, even with gen_twopix() calls moved out, was inefficient and branchy, so let's 2) rewrite gen_text() loop so it uses less variables + unroll char horizontal-rendering loop + instantiate 3 code paths for pixelsizes 2,3 and 4 so that in all inner loops we don't have to branch or make indirections (*). Done all above reworks, for gen_text() we get nice, non-branchy streamlined code (showing loop for pixelsize=2): ? cmp $0x2,%eax ? ? jne 26 ? mov -0x18(%ebp),%eax ? mov -0x20(%ebp),%edi ? imul -0x20(%ebp),%eax ? movzwl 0x3ffc(%ebx),%esi 0,08 ? movzwl 0x4000(%ebx),%ecx 0,04 ? add %edi,%edi ? mov 0x0,%ebx 0,51 ? mov %edi,-0x1c(%ebp) ? mov %ebx,-0x14(%ebp) ? movl $0x0,-0x10(%ebp) ? lea 0x20(%edx,%eax,2),%eax ? mov %eax,-0x18(%ebp) ? xchg %ax,%ax 0,04 ? a0: mov 0x8(%ebp),%ebx ? mov -0x18(%ebp),%eax 0,04 ? movzbl (%ebx),%edx 0,16 ? test %dl,%dl 0,04 ? ? je 128 0,08 ? lea 0x0(%esi),%esi 1,61 ? b0:???shl $0x4,%edx 1,02 ? ? mov -0x14(%ebp),%edi 2,04 ? ? add -0x10(%ebp),%edx 2,24 ? ? lea 0x1(%ebx),%ebx 0,27 ? ? movzbl (%edi,%edx,1),%edx 9,92 ? ? mov %esi,%edi 0,39 ? ? test %dl,%dl 2,04 ? ? cmovns %ecx,%edi 4,63 ? ? test $0x40,%dl 0,55 ? ? mov %di,(%eax) 3,76 ? ? mov %esi,%edi 0,71 ? ? cmove %ecx,%edi 3,41 ? ? test $0x20,%dl 0,75 ? ? mov %di,0x2(%eax) 2,43 ? ? mov %esi,%edi 0,59 ? ? cmove %ecx,%edi 4,59 ? ? test $0x10,%dl 0,67 ? ? mov %di,0x4(%eax) 2,55 ? ? mov %esi,%edi 0,78 ? ? cmove %ecx,%edi 4,31 ? ? test $0x8,%dl 0,67 ? ? mov %di,0x6(%eax) 5,76 ? ? mov %esi,%edi 1,80 ? ? cmove %ecx,%edi 4,20 ? ? test $0x4,%dl 0,86 ? ? mov %di,0x8(%eax) 2,98 ? ? mov %esi,%edi 1,37 ? ? cmove %ecx,%edi 4,67 ? ? test $0x2,%dl 0,20 ? ? mov %di,0xa(%eax) 2,78 ? ? mov %esi,%edi 0,75 ? ? cmove %ecx,%edi 3,92 ? ? and $0x1,%edx 0,75 ? ? mov %esi,%edx 2,59 ? ? mov %di,0xc(%eax) 0,59 ? ? cmove %ecx,%edx 3,10 ? ? mov %dx,0xe(%eax) 2,39 ? ? add $0x10,%eax 0,51 ? ? movzbl (%ebx),%edx 2,86 ? ? test %dl,%dl 2,31 ? ???jne b0 0,04 ?128: addl $0x1,-0x10(%ebp) 4,00 ? mov -0x1c(%ebp),%eax 0,04 ? add %eax,-0x18(%ebp) 0,08 ? cmpl $0x10,-0x10(%ebp) ? ? jne a0 which almost goes away from the profile: # cmdline : /home/kirr/local/perf/bin/perf record -g -a sleep 20 # Samples: 49K of event 'cycles' # Event count (approx.): 16799780016 # # Overhead Command Shared Object Symbol # ........ ............... .................... # 27.51% rawv libc-2.13.so [.] __memcpy_ssse3 23.77% vivi-* [kernel.kallsyms] [k] memcpy 9.96% Xorg [unknown] [.] 0xa76f5e12 4.94% vivi-* [vivi] [k] gen_text.constprop.6 4.44% rawv [vivi] [k] gen_twopix 3.17% vivi-* [vivi] [k] vivi_fillbuff 2.45% rawv [vivi] [k] precalculate_line 1.20% swapper [kernel.kallsyms] [k] read_hpet i.e. gen_twopix() overhead dropped from 49% to 4% and gen_text() loops from ~8% to ~4%, and overal cycles count dropped from 31551930117 to 16799780016 which is ~1.9x whole workload speedup. (*) for RGB24 rendering I've introduced x24, which could be thought as synthetic u24 for simplifying the code. That's done because for memcpy used for conditional assignment, gcc generates suboptimal code with more indirections. Fortunately, in C struct assignment is builtin and that's all we need from pixeltype for font rendering. Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media/platform')
-rw-r--r--drivers/media/platform/vivi.c61
1 files changed, 43 insertions, 18 deletions
diff --git a/drivers/media/platform/vivi.c b/drivers/media/platform/vivi.c
index c2f424f32450..3801a8d00946 100644
--- a/drivers/media/platform/vivi.c
+++ b/drivers/media/platform/vivi.c
@@ -240,6 +240,7 @@ struct vivi_dev {
u8 line[MAX_WIDTH * 8];
unsigned int pixelsize;
u8 alpha_component;
+ u32 textfg, textbg;
};
/* ------------------------------------------------------------------
@@ -520,33 +521,54 @@ static void precalculate_line(struct vivi_dev *dev)
}
}
+/* need this to do rgb24 rendering */
+typedef struct { u16 __; u8 _; } __attribute__((packed)) x24;
+
static void gen_text(struct vivi_dev *dev, char *basep,
int y, int x, char *text)
{
int line;
+ unsigned int width = dev->width;
/* Checks if it is possible to show string */
- if (y + 16 >= dev->height || x + strlen(text) * 8 >= dev->width)
+ if (y + 16 >= dev->height || x + strlen(text) * 8 >= width)
return;
/* Print stream time */
- for (line = y; line < y + 16; line++) {
- int j = 0;
- char *pos = basep + line * dev->width * dev->pixelsize + x * dev->pixelsize;
- char *s;
-
- for (s = text; *s; s++) {
- u8 chr = font8x16[*s * 16 + line - y];
- int i;
-
- for (i = 0; i < 7; i++, j++) {
- /* Draw white font on black background */
- if (chr & (1 << (7 - i)))
- gen_twopix(dev, pos + j * dev->pixelsize, WHITE, (x+y) & 1);
- else
- gen_twopix(dev, pos + j * dev->pixelsize, TEXT_BLACK, (x+y) & 1);
- }
- }
+#define PRINTSTR(PIXTYPE) do { \
+ PIXTYPE fg; \
+ PIXTYPE bg; \
+ memcpy(&fg, &dev->textfg, sizeof(PIXTYPE)); \
+ memcpy(&bg, &dev->textbg, sizeof(PIXTYPE)); \
+ \
+ for (line = 0; line < 16; line++) { \
+ PIXTYPE *pos = (PIXTYPE *)( basep + ((y + line) * width + x) * sizeof(PIXTYPE) ); \
+ u8 *s; \
+ \
+ for (s = text; *s; s++) { \
+ u8 chr = font8x16[*s * 16 + line]; \
+ \
+ pos[0] = (chr & (0x01 << 7) ? fg : bg); \
+ pos[1] = (chr & (0x01 << 6) ? fg : bg); \
+ pos[2] = (chr & (0x01 << 5) ? fg : bg); \
+ pos[3] = (chr & (0x01 << 4) ? fg : bg); \
+ pos[4] = (chr & (0x01 << 3) ? fg : bg); \
+ pos[5] = (chr & (0x01 << 2) ? fg : bg); \
+ pos[6] = (chr & (0x01 << 1) ? fg : bg); \
+ pos[7] = (chr & (0x01 << 0) ? fg : bg); \
+ \
+ pos += 8; \
+ } \
+ } \
+} while (0)
+
+ switch (dev->pixelsize) {
+ case 2:
+ PRINTSTR(u16); break;
+ case 4:
+ PRINTSTR(u32); break;
+ case 3:
+ PRINTSTR(x24); break;
}
}
@@ -570,6 +592,9 @@ static void vivi_fillbuff(struct vivi_dev *dev, struct vivi_buffer *buf)
/* Updates stream time */
+ gen_twopix(dev, (u8 *)&dev->textbg, TEXT_BLACK, /*odd=*/ 0);
+ gen_twopix(dev, (u8 *)&dev->textfg, WHITE, /*odd=*/ 0);
+
dev->ms += jiffies_to_msecs(jiffies - dev->jiffies);
dev->jiffies = jiffies;
ms = dev->ms;

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