* [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions
@ 2012-01-03 13:32 Avi Kivity
2012-01-12 13:46 ` Avi Kivity
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Avi Kivity @ 2012-01-03 13:32 UTC (permalink / raw)
To: qemu-devel
ppm_save() spends upwards of 50% of its time doing divisions. Replace them
with shifts.
Signed-off-by: Avi Kivity <avi@redhat.com>
---
hw/vga.c | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/hw/vga.c b/hw/vga.c
index ca79aa1..a228cde 100644
--- a/hw/vga.c
+++ b/hw/vga.c
@@ -2370,12 +2370,10 @@ int ppm_save(const char *filename, struct DisplaySurface *ds)
v = *(uint32_t *)d;
else
v = (uint32_t) (*(uint16_t *)d);
- r = ((v >> ds->pf.rshift) & ds->pf.rmax) * 256 /
- (ds->pf.rmax + 1);
- g = ((v >> ds->pf.gshift) & ds->pf.gmax) * 256 /
- (ds->pf.gmax + 1);
- b = ((v >> ds->pf.bshift) & ds->pf.bmax) * 256 /
- (ds->pf.bmax + 1);
+ /* Limited to 8 or fewer bits per channel: */
+ r = ((v >> ds->pf.rshift) & ds->pf.rmax) << (8 - ds->pf.rbits);
+ g = ((v >> ds->pf.gshift) & ds->pf.gmax) << (8 - ds->pf.gbits);
+ b = ((v >> ds->pf.bshift) & ds->pf.bmax) << (8 - ds->pf.bbits);
*pbuf++ = r;
*pbuf++ = g;
*pbuf++ = b;
--
1.7.7.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions
2012-01-03 13:32 [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions Avi Kivity
@ 2012-01-12 13:46 ` Avi Kivity
2012-01-12 15:16 ` Alon Levy
2012-01-12 16:54 ` Anthony Liguori
2 siblings, 0 replies; 5+ messages in thread
From: Avi Kivity @ 2012-01-12 13:46 UTC (permalink / raw)
To: qemu-devel
On 01/03/2012 03:32 PM, Avi Kivity wrote:
> ppm_save() spends upwards of 50% of its time doing divisions. Replace them
> with shifts.
>
>
Pings.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions
2012-01-03 13:32 [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions Avi Kivity
2012-01-12 13:46 ` Avi Kivity
@ 2012-01-12 15:16 ` Alon Levy
2012-01-12 15:19 ` Alon Levy
2012-01-12 16:54 ` Anthony Liguori
2 siblings, 1 reply; 5+ messages in thread
From: Alon Levy @ 2012-01-12 15:16 UTC (permalink / raw)
To: Avi Kivity; +Cc: qemu-devel
On Tue, Jan 03, 2012 at 03:32:57PM +0200, Avi Kivity wrote:
> ppm_save() spends upwards of 50% of its time doing divisions. Replace them
> with shifts.
>
Reviewed-by: Alon Levy <alevy@redhat.com>
rmax/bmax/gmax are all uint8_t atm, could add a compilation error if
sizeof(bmax)!=1 ever.
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
> hw/vga.c | 10 ++++------
> 1 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/hw/vga.c b/hw/vga.c
> index ca79aa1..a228cde 100644
> --- a/hw/vga.c
> +++ b/hw/vga.c
> @@ -2370,12 +2370,10 @@ int ppm_save(const char *filename, struct DisplaySurface *ds)
> v = *(uint32_t *)d;
> else
> v = (uint32_t) (*(uint16_t *)d);
> - r = ((v >> ds->pf.rshift) & ds->pf.rmax) * 256 /
> - (ds->pf.rmax + 1);
> - g = ((v >> ds->pf.gshift) & ds->pf.gmax) * 256 /
> - (ds->pf.gmax + 1);
> - b = ((v >> ds->pf.bshift) & ds->pf.bmax) * 256 /
> - (ds->pf.bmax + 1);
> + /* Limited to 8 or fewer bits per channel: */
> + r = ((v >> ds->pf.rshift) & ds->pf.rmax) << (8 - ds->pf.rbits);
> + g = ((v >> ds->pf.gshift) & ds->pf.gmax) << (8 - ds->pf.gbits);
> + b = ((v >> ds->pf.bshift) & ds->pf.bmax) << (8 - ds->pf.bbits);
> *pbuf++ = r;
> *pbuf++ = g;
> *pbuf++ = b;
> --
> 1.7.7.1
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions
2012-01-12 15:16 ` Alon Levy
@ 2012-01-12 15:19 ` Alon Levy
0 siblings, 0 replies; 5+ messages in thread
From: Alon Levy @ 2012-01-12 15:19 UTC (permalink / raw)
To: Avi Kivity, qemu-devel
On Thu, Jan 12, 2012 at 05:16:03PM +0200, Alon Levy wrote:
> On Tue, Jan 03, 2012 at 03:32:57PM +0200, Avi Kivity wrote:
> > ppm_save() spends upwards of 50% of its time doing divisions. Replace them
> > with shifts.
> >
>
> Reviewed-by: Alon Levy <alevy@redhat.com>
>
> rmax/bmax/gmax are all uint8_t atm, could add a compilation error if
> sizeof(bmax)!=1 ever.
meant {r,g,b}bits.
>
> > Signed-off-by: Avi Kivity <avi@redhat.com>
> > ---
> > hw/vga.c | 10 ++++------
> > 1 files changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/hw/vga.c b/hw/vga.c
> > index ca79aa1..a228cde 100644
> > --- a/hw/vga.c
> > +++ b/hw/vga.c
> > @@ -2370,12 +2370,10 @@ int ppm_save(const char *filename, struct DisplaySurface *ds)
> > v = *(uint32_t *)d;
> > else
> > v = (uint32_t) (*(uint16_t *)d);
> > - r = ((v >> ds->pf.rshift) & ds->pf.rmax) * 256 /
> > - (ds->pf.rmax + 1);
> > - g = ((v >> ds->pf.gshift) & ds->pf.gmax) * 256 /
> > - (ds->pf.gmax + 1);
> > - b = ((v >> ds->pf.bshift) & ds->pf.bmax) * 256 /
> > - (ds->pf.bmax + 1);
> > + /* Limited to 8 or fewer bits per channel: */
> > + r = ((v >> ds->pf.rshift) & ds->pf.rmax) << (8 - ds->pf.rbits);
> > + g = ((v >> ds->pf.gshift) & ds->pf.gmax) << (8 - ds->pf.gbits);
> > + b = ((v >> ds->pf.bshift) & ds->pf.bmax) << (8 - ds->pf.bbits);
> > *pbuf++ = r;
> > *pbuf++ = g;
> > *pbuf++ = b;
> > --
> > 1.7.7.1
> >
> >
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions
2012-01-03 13:32 [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions Avi Kivity
2012-01-12 13:46 ` Avi Kivity
2012-01-12 15:16 ` Alon Levy
@ 2012-01-12 16:54 ` Anthony Liguori
2 siblings, 0 replies; 5+ messages in thread
From: Anthony Liguori @ 2012-01-12 16:54 UTC (permalink / raw)
To: Avi Kivity; +Cc: qemu-devel
On 01/03/2012 07:32 AM, Avi Kivity wrote:
> ppm_save() spends upwards of 50% of its time doing divisions. Replace them
> with shifts.
>
> Signed-off-by: Avi Kivity<avi@redhat.com>
Applied. Thanks.
Regards,
Anthony Liguori
> ---
> hw/vga.c | 10 ++++------
> 1 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/hw/vga.c b/hw/vga.c
> index ca79aa1..a228cde 100644
> --- a/hw/vga.c
> +++ b/hw/vga.c
> @@ -2370,12 +2370,10 @@ int ppm_save(const char *filename, struct DisplaySurface *ds)
> v = *(uint32_t *)d;
> else
> v = (uint32_t) (*(uint16_t *)d);
> - r = ((v>> ds->pf.rshift)& ds->pf.rmax) * 256 /
> - (ds->pf.rmax + 1);
> - g = ((v>> ds->pf.gshift)& ds->pf.gmax) * 256 /
> - (ds->pf.gmax + 1);
> - b = ((v>> ds->pf.bshift)& ds->pf.bmax) * 256 /
> - (ds->pf.bmax + 1);
> + /* Limited to 8 or fewer bits per channel: */
> + r = ((v>> ds->pf.rshift)& ds->pf.rmax)<< (8 - ds->pf.rbits);
> + g = ((v>> ds->pf.gshift)& ds->pf.gmax)<< (8 - ds->pf.gbits);
> + b = ((v>> ds->pf.bshift)& ds->pf.bmax)<< (8 - ds->pf.bbits);
> *pbuf++ = r;
> *pbuf++ = g;
> *pbuf++ = b;
^ permalink raw reply [flat|nested] 5+ messages in thread
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2012-01-03 13:32 [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions Avi Kivity
2012-01-12 13:46 ` Avi Kivity
2012-01-12 15:16 ` Alon Levy
2012-01-12 15:19 ` Alon Levy
2012-01-12 16:54 ` Anthony Liguori
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