# QT GUI time sink (float) unnecessary memmove()?

**URL:** <https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770>\
**Category:** GNU Radio\
**Created:** [March 28, 2015, 7:01pm UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770 "2015-03-28T19:01:28Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [March 28, 2015, 7:01pm UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/1 "2015-03-28T19:01:28Z")

</div>

Hi,

Can this memmove() be safely skipped

> <https://github.com/gnuradio/gnuradio/blob/master/gr-qtgui/lib/time_sink_f_impl.cc#L627>

if ((d\_start == 0) || (gr::high\_res\_timer\_now() - d\_last\_time \>  
d\_update\_time))?

I think it can, but I am not sure.

With some high throughput, high sample rate flowgraphs, ps shows my  
time\_sink\_f thread taking up ~41% of a CPU and oprofile shows memmove()  
as the number 2 pig on the list:

CPU: Intel Sandy Bridge microarchitecture, speed 3.5e+06 MHz (estimated)  
Counted CPU\_CLK\_UNHALTED events (Clock cycles when not halted) with a  
unit mask of 0x00 (No unit mask) count 90000  
samples % image name symbol name  
24498 33.9825 libvolk.so.0.0.0 volk\_32f\_convert\_64f\_u\_avx  
14278 19.8058 libc-2.18.so \_\_memmove\_ssse3\_back  
7488 10.3870 no-vmlinux /no-vmlinux  
2668 3.7009 libgnuradio-qtgui-3.7.7git.so.0.0.0  
gr::qtgui::time\_sink\_f\_impl::\_test\_trigger\_slope(float const\*) const  
2073 2.8756 libpthread-2.18.so pthread\_mutex\_lock

The volk\_32f\_convert\_64f\_u\_avx() call is unavoidable as Qwt wants  
doubles for plotting and not floats. But it might also be able to be  
deferred to the very end when the decision to plot is known for sure.  
(But that’s more surgery than I care to take on at the moment.)

Regards,  
Andy

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 28, 2015, 7:14pm UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/2 "2015-03-28T19:14:33Z")

</div>

On Sat, Mar 28, 2015 at 11:00 AM, Andy W.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> I think it can, but I am not sure.  
> 14278 19.8058 libc-2.18.so \_\_memmove\_ssse3\_back  
> Regards,  
> Andy

The for loop there is in case we’re triggering with a delay set, so that  
sets d\_start into the buffers. But we pass the vector of buffers to the  
plotting widget, which will start at index 0. There are a couple of  
things  
that could work here. We add an argument to TimeUpdateEvent that adds  
the  
index value. We could also only do the memcpy if d\_start \> 0. But  
thinking  
about the volk convert function, that’s both copying the data from the  
input buffer into the internal buffer as well as performing the  
conversion.  
We can’t just hold data in the input since we don’t want to back up the  
data until we’re ready to plot both with timing and with a full enough  
buffer – it’s just sampling a section at a time and drops everything in  
between. That part could be converted into a memcpy instead of the volk  
convert. Then, when we’re ready to plot, we call the volk convert that  
also  
does the move from d\_start to 0, so it combines those two elements.

Thoughts on those proposals?

Tom

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 28, 2015, 7:46pm UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/3 "2015-03-28T19:46:55Z")

</div>

Hi Tom:

On Sat, 2015-03-28 at 11:12 -0700, Tom R. wrote:

> On Sat, Mar 28, 2015 at 11:00 AM, Andy W.  
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ```
> Can this memmove() be safely skipped
> 
> ```

> <https://github.com/gnuradio/gnuradio/blob/master/gr-qtgui/lib/time_sink_f_impl.cc#L627>

[snip]

> ```
> The volk_32f_convert_64f_u_avx() call is unavoidable as Qwt
> wants
> doubles for plotting and not floats. But it might also be able
> to be
> deferred to the very end when the decision to plot is known
> for sure.
> (But that's more surgery than I care to take on at the
> moment.)
> 
> ```

> The for loop there is in case we’re triggering with a delay set, so  
> that sets d\_start into the buffers. But we pass the vector of buffers  
> to the plotting widget, which will start at index 0. There are a  
> couple of things that could work here. We add an argument to  
> TimeUpdateEvent that adds the index value. We could also only do the  
> memcpy if d\_start \> 0.

Modifying TimeUpdateEvent() would work. I don’t know how much ripple  
that would cause in forcing other code to change.

BTW, I do use delayed trigger.  
I did a hack to only do the memmove() only if d\_start != 0 _and_ we were  
going to plot in this call to work(). See below for results.

> But thinking about the volk convert function, that’s both copying the  
> data from the input buffer into the internal buffer as well as  
> performing the conversion. We can’t just hold data in the input since  
> we don’t want to back up the data until we’re ready to plot both with  
> timing and with a full enough buffer – it’s just sampling a section  
> at a time and drops everything in between.

Right.

> That part could be converted into a memcpy instead of the volk  
> convert. Then, when we’re ready to plot, we call the volk convert that  
> also does the move from d\_start to 0, so it combines those two  
> elements.

Yeah, that’s the surgery part. 🙂 It would require adding a new set of  
buffers to hold floats objects, and then convert them when a  
determination to plot was made.

This also affects the memmove() of the tail for the trigger delay. It  
would operate on the new set of float buffers (vs the buffers holding  
doubles).

> Thoughts on those proposals?

> Tom

I just did this quick hack and tested it:

```
    --- a/gr-qtgui/lib/time_sink_f_impl.cc
    +++ b/gr-qtgui/lib/time_sink_f_impl.cc
    @@ -622,13 +622,15 @@ namespace gr {

           // If we've have a trigger and a full d_size of items in 

```

the buffers, plo  
if((d\_triggered) && (d\_index == d\_end)) {  
- // Copy data to be plotted to start of buffers.  
- for(n = 0; n \< d\_nconnections; n++) {  
- memmove(d\_buffers[n], &d\_buffers[n][d\_start],  
d\_size_sizeof(double));  
- }  
-  
// Plot if we are able to update  
if(gr::high\_res\_timer\_now() - d\_last\_time \>  
d\_update\_time) {  
+ if(d\_start != 0) {  
+ // Copy data to be plotted to start of buffers.  
+ for(n = 0; n \< d\_nconnections; n++) {  
+ memmove(d\_buffers[n],  
+ &d\_buffers[n][d\_start],  
d\_size_sizeof(double));  
+ }  
+ }  
d\_last\_time = gr::high\_res\_timer\_now();

I got about 2-5% of my CPU back and memmove() fell into the “I don’t  
care” part of the oprofile stats. 🙂  
Everything seemed ok in the GUI, but my input causes triggers to happen  
quite often, so I haven’t tested infrequent trigger cases.

CPU: Intel Sandy Bridge microarchitecture, speed 3.5e+06 MHz (estimated)  
Counted CPU\_CLK\_UNHALTED events (Clock cycles when not halted) with a  
unit mask of 0x00 (No unit mask) count 100000  
samples % image name symbol name  
78158 39.0737 libvolk.so.0.0.0 volk\_32f\_convert\_64f\_u\_avx  
22777 11.3870 no-vmlinux /no-vmlinux  
13972 6.9851 libgnuradio-qtgui-3.7.7git.so.0.0.0  
gr::qtgui::time\_sink\_f\_impl::\_test\_trigger\_slope(float const\*) const  
7781 3.8900 libgnuradio-qtgui-3.7.7git.so.0.0.0  
gr::qtgui::time\_sink\_f\_impl::\_test\_trigger\_norm(int, std::vector\<void  
const\*, std::allocator\<void const\*\> \>)  
7236 3.6175 libpthread-2.18.so pthread\_mutex\_lock  
6163 3.0811 libgnuradio-runtime-3.7.7git.so.0.0.0  
boost::detail::sp\_counted\_base::release()  
5942 2.9706 libpthread-2.18.so pthread\_mutex\_unlock  
4947 2.4732 libgnuradio-runtime-3.7.7git.so.0.0.0  
gr::block\_executor::run\_one\_iteration()  
3826 1.9127 libgnuradio-runtime-3.7.7git.so.0.0.0  
gr::block\_detail::input(unsigned int)  
3555 1.7773 libstdc++.so.6.0.19  
/usr/lib64/libstdc++.so.6.0.19  
3206 1.6028 libc-2.18.so \_\_memmove\_ssse3\_back

Regards,  
Andy

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 29, 2015, 1:08am UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/4 "2015-03-29T01:08:21Z")

</div>

On Sat, Mar 28, 2015 at 12:50 PM, Andy W.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> > > 
> > 
> > would operate on the new set of float buffers (vs the buffers holding
> 
> > 13972 6.9851 libgnuradio-qtgui-3.7.7git.so.0.0.0  
> > 3826 1.9127 libgnuradio-runtime-3.7.7git.so.0.0.0  
> > samples % image name symbol name  
> > 2091 2.6980 libstdc++.so.6.0.19 /usr/lib64/libstdc++.so.6.0.19  
> > Andy

Andy,

Excellent!

I’ve got a few other minor patches for some things, I’ll put this in  
there  
to and test on my end as well.

Tom

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 28, 2015, 8:52pm UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/5 "2015-03-28T20:52:16Z")

</div>

On Sat, 2015-03-28 at 14:45 -0400, Andy W. wrote:

> [snip]
> 
> > ```
> > The volk_32f_convert_64f_u_avx() call is unavoidable as Qwt
> > wants
> > doubles for plotting and not floats. But it might also be able
> > to be
> > deferred to the very end when the decision to plot is known
> > for sure.
> > (But that's more surgery than I care to take on at the
> > moment.)
> > 
> > ```

> > That part could be converted into a memcpy instead of the volk  
> > doubles).
> 
> > Thoughts on those proposals?

Your proposal for implementing memcpy() and deferring volk\_\*() to do the  
conversion and “memmove” in one step is great! 🙂

I just implemented it, and the time\_sink\_f thread has gone from 41.5%  
CPU down to 29.1% CPU in my tests. 🙂 memcpy() now dominates the  
thread, but that’s to be expected.

With my initial hack:

> 4947 2.4732 libgnuradio-runtime-3.7.7git.so.0.0.0  
> gr::block\_executor::run\_one\_iteration()  
> 3826 1.9127 libgnuradio-runtime-3.7.7git.so.0.0.0  
> gr::block\_detail::input(unsigned int)  
> 3555 1.7773 libstdc++.so.6.0.19 /usr/lib64/libstdc++.so.6.0.19  
> 3206 1.6028 libc-2.18.so \_\_memmove\_ssse3\_back  
> […]

With my implementation of your suggestion:

CPU: Intel Sandy Bridge microarchitecture, speed 3.5e+06 MHz (estimated)  
Counted CPU\_CLK\_UNHALTED events (Clock cycles when not halted) with a  
unit mask of 0x00 (No unit mask) count 90000  
samples % image name symbol name  
27595 35.6051 libc-2.18.so \_\_memcpy\_sse2\_unaligned  
12225 15.7736 no-vmlinux /no-vmlinux  
4051 5.2269 libpthread-2.18.so pthread\_mutex\_lock  
3739 4.8243 libgnuradio-runtime-3.7.7git.so.0.0.0  
boost::detail::sp\_counted\_base::release()  
3362 4.3379 libpthread-2.18.so pthread\_mutex\_unlock  
2876 3.7108 libgnuradio-runtime-3.7.7git.so.0.0.0  
gr::block\_executor::run\_one\_iteration()  
2364 3.0502 libgnuradio-runtime-3.7.7git.so.0.0.0  
gr::block\_detail::input(unsigned int)  
2091 2.6980 libstdc++.so.6.0.19  
/usr/lib64/libstdc++.so.6.0.19  
1388 1.7909 libgnuradio-runtime-3.7.7git.so.0.0.0  
gr::tpb\_detail::notify\_upstream(gr::block\_detail\*)  
1138 1.4683 libc-2.18.so \_\_memmove\_ssse3\_back  
[…]  
2 0.0026 libvolk.so.0.0.0 \_\_volk\_32f\_convert\_64f\_d  
[…]  
1 0.0013 libvolk.so.0.0.0 volk\_32f\_convert\_64f\_a\_avx

Regards,  
Andy

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 30, 2015, 2:22am UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/6 "2015-03-30T02:22:29Z")

</div>

On Sat, Mar 28, 2015 at 5:32 PM, Andy W.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> When testing, I used 5 float streams rumning at over 150 Msps each, with  
> 15 microsecomd bursts of 50 MHz at about 10 microseconds apart. I used  
> enough x points to see two bursts on the gui. Normal trigger. (Free or auto  
> trigger moght be too taxing.)
> 
> -Regards  
> Andy

Andy, if you have a chance, can you check out this new branch:

[https://github.com/trondeau/gnuradio/tree/qtgui/controlpanel](https://github.com/trondeau/gnuradio/tree/qtgui/controlpanel)

It adds the fixes that we talked about. I just want to verify that  
things  
are still looking and behaving well for you.

The other trick of this branch is if you go into the QT GUI Time Sink  
properties and turn “Control Panel” to Yes. I wouldn’t mind a quick bit  
of  
feedback there, either.

Tom

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 29, 2015, 1:34am UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/7 "2015-03-29T01:34:14Z")

</div>

When testing, I used 5 float streams rumning at over 150 Msps each, with  
15 microsecomd bursts of 50 MHz at about 10 microseconds apart. I used  
enough x points to see two bursts on the gui. Normal trigger. (Free  
or auto trigger moght be too taxing.)

-Regards  
Andy

---

<div class="post-metadata">

**Author:** ![andywatts](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/d78d45/32.png) [@andywatts](https://www.ruby-forum.com/u/andywatts)\
**Post date:** [March 31, 2015, 12:15am UTC](https://www.ruby-forum.com/t/qt-gui-time-sink-float-unnecessary-memmove/234770/8 "2015-03-31T00:15:24Z")

</div>

On Sun, 2015-03-29 at 17:20 -0700, Tom R. wrote:

> On Sat, Mar 28, 2015 at 5:32 PM, Andy W.  
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Andy, if you have a chance, can you check out this new branch:
> 
> [https://github.com/trondeau/gnuradio/tree/qtgui/controlpanel](https://github.com/trondeau/gnuradio/tree/qtgui/controlpanel)
> 
> It adds the fixes that we talked about. I just want to verify that  
> things are still looking and behaving well for you.

I had time to inspect the change for time\_sink\_f\_impl.\* but haven’t had  
time to test yet. What you did was very close to what I did (including  
naming the new buffers ‘d\_fbuffers’ 🙂 ), but I will suggest two  
improvements:

1. The size of the allocated double ‘d\_buffers’ arrays can now be  
reduced from d\_buffer\_size to d\_size, so they only take up 1/2 as much  
memory.

2. (I think) You can defer the call to volk\_32f\_convert\_64f() even more,  
to when you know for sure plotting is going to happen in the clause that  
checks the update time. See the patch in line below.  
It works for me.

> The other trick of this branch is if you go into the QT GUI Time Sink  
> properties and turn “Control Panel” to Yes. I wouldn’t mind a quick  
> bit of feedback there, either.

I’ll have some time on Wednesday to recompile and evaluate.

> Tom

Regards,  
Andy

diff --git a/gr-qtgui/lib/time\_sink\_f\_impl.cc  
b/gr-qtgui/lib/time\_sink\_f\_impl.cc  
index 8e45e2c..5aa126d 100644  
— a/gr-qtgui/lib/time\_sink\_f\_impl.cc  
+++ b/gr-qtgui/lib/time\_sink\_f\_impl.cc  
@@ -68,9 +68,12 @@ namespace gr {  
d\_main\_gui = NULL;

```
   for(int n = 0; n < d_nconnections; n++) {

```

- 

d\_buffers.push\_back((double\*)volk\_malloc(d\_buffer\_size\*sizeof(double),

- d\_fbuffers.push\_back((float\*)volk\_malloc(d\_buffer\_size\*sizeof(float),  
volk\_get\_alignment()));

- memset(d\_buffers[n], 0, d\_buffer\_size\*sizeof(double));

- memset(d\_fbuffers[n], 0, d\_buffer\_size\*sizeof(float));
- d\_buffers.push\_back((double\*)volk\_malloc(d\_size\*sizeof(double),
- 

volk\_get\_alignment()));

- memset(d\_buffers[n], 0, d\_size\*sizeof(double));  
}

@@ -96,6 +99,7 @@ namespace gr {

```
   // d_main_gui is a qwidget destroyed with its parent
   for(int n = 0; n < d_nconnections; n++) {

```

- volk\_free(d\_fbuffers[n]);  
volk\_free(d\_buffers[n]);  
}

@@ -329,10 +333,14 @@ namespace gr {

// Resize buffers and replace data  
for(int n = 0; n \< d\_nconnections; n++) {

- volk\_free(d\_fbuffers[n]);
- d\_fbuffers[n] = (float\*)volk\_malloc(d\_buffer\_size\*sizeof(float),
- 

```
                                         volk_get_alignment());

```

- memset(d\_fbuffers[n], 0, d\_buffer\_size\*sizeof(float));  
volk\_free(d\_buffers[n]);

- d\_buffers[n] = (double\*)volk\_malloc(d\_buffer\_size\*sizeof(double),

- d\_buffers[n] = (double\*)volk\_malloc(d\_size\*sizeof(double),  
volk\_get\_alignment());

- memset(d\_buffers[n], 0, d\_buffer\_size\*sizeof(double));

- memset(d\_buffers[n], 0, d\_size\*sizeof(double));  
}

@@ -427,7 +435,7 @@ namespace gr {  
int n;  
if(d\_trigger\_delay) {  
for(n = 0; n \< d\_nconnections; n++) {

- 

```
     memmove(d_buffers[n], &d_buffers[n][d_size-d_trigger_delay], 

```

d\_trigger\_delay\*sizeof(double));

- 

```
     memmove(d_fbuffers[n], 

```

&d\_fbuffers[n][d\_size-d\_trigger\_delay], d\_trigger\_delay\*sizeof(float));  
}

```
     // Also move the offsets of any tags that occur in the tail

```

@@ -606,8 +614,7 @@ namespace gr {  
// Copy data into the buffers.  
for(n = 0; n \< d\_nconnections; n++) {  
in = (const float\*)input\_items[idx];

- 

```
   volk_32f_convert_64f(&d_buffers[n][d_index],

```

- 

```
                        &in[1], nitems);

```

- 

```
   memcpy(&d_fbuffers[n][d_index], &in[1], nitems*sizeof(float));

   uint64_t nr = nitems_read(idx);
   std::vector<gr::tag_t> tags;

```

@@ -622,13 +629,13 @@ namespace gr {

```
   // If we've have a trigger and a full d_size of items in the 

```

buffers, plot.  
if((d\_triggered) && (d\_index == d\_end)) {

- 

```
   // Copy data to be plotted to start of buffers.

```

- 

```
   for(n = 0; n < d_nconnections; n++) {

```

- 

```
     memmove(d_buffers[n], &d_buffers[n][d_start], 

```

d\_size\*sizeof(double));

- 

```
   }

```

- 

```
   // Plot if we are able to update
   if(gr::high_res_timer_now() - d_last_time > d_update_time) {

```

- 

```
     // Convert and copy data to be plotted to start of buffers.

```

- 

```
     for(n = 0; n < d_nconnections; n++) {

```

- 

```
       volk_32f_convert_64f(&d_buffers[n][0],

```

- 

```
                            &d_fbuffers[n][d_start], d_size);

```

- 

```
     }
     d_last_time = gr::high_res_timer_now();
     d_qApplication->postEvent(d_main_gui,
                               new TimeUpdateEvent(d_buffers, 

```

d\_size, d\_tags));  
diff --git a/gr-qtgui/lib/time\_sink\_f\_impl.h  
b/gr-qtgui/lib/time\_sink\_f\_impl.h  
index 2da1db9..d8e2261 100644  
— a/gr-qtgui/lib/time\_sink\_f\_impl.h  
+++ b/gr-qtgui/lib/time\_sink\_f\_impl.h  
@@ -41,6 +41,7 @@ namespace gr {  
int d\_nconnections;

```
   int d_index, d_start, d_end;

```

- 

```
 std::vector<float*> d_fbuffers;
 std::vector<double*> d_buffers;
 std::vector< std::vector<gr::tag_t> > d_tags;

```