[Python-Dev] new buffer in python2.7

Wed Oct 27 16:32:02 CEST 2010

Sorry, here the tables properly formatted:

Function Name

Inclusive Samples

Exclusive Samples

Inclusive Samples %

Exclusive Samples %

apply_slice

8.997

468

62,23

3,24

_PyObject_GetItem

6.257

400

43,28

2,77

memory_subscript

5.857

1.051

40,51

7,27

_PyMemoryView_FromBuffer

2.642

455

18,27

3,15

memory_dealloc

1.572

297

10,87

2,05

_PyObject_Malloc

1.374

1.374

9,50

9,50

__PyObject_GC_New

1.256

236

8,69

1,63

_PySlice_New

1.211

333

8,38

2,30

slice_dealloc

1.061

769

7,34

5,32

__PyObject_GC_Malloc

1.022

293

7,07

2,03

bytearray_getbuffer

987

354

6,83

2,45

dup_buffer

932

932

6,45

6,45

Function Name

Inclusive Samples

Exclusive Samples

Inclusive Samples %

Exclusive Samples %

apply_slice

3.888

502

48,44

6,25

_PySequence_GetSlice

3.039

350

37,86

4,36

string_slice

2.689

281

33,50

3,50

_PyString_FromStringAndSize

2.409

575

30,01

7,16

[MSVCR90.dll]

1.413

1.407

17,61

17,53

string_dealloc

467

150

5,82

1,87

_PyObject_Malloc

379

379

4,72

4,72

_PyObject_Free

378

378

4,71

4,71

__PyEval_SliceIndex

347

347

4,32

4,32

-----Original Message-----
From: python-dev-bounces+kristjan=ccpgames.com at python.org [mailto:python-dev-bounces+kristjan=ccpgames.com at python.org] On Behalf Of Kristján Valur Jónsson
Sent: Wednesday, October 27, 2010 20:00
To: Antoine Pitrou; python-dev at python.org
Subject: Re: [Python-Dev] new buffer in python2.7

Ah, well in 2.7 you don't have the luxury of a bytes object.  A str() would be similar in 2.7 Anyway, isn't the "bytes" object immutable? In that case, it is not a useful target for a sock.recv_into() call.

Calling getbuffer on a bytearray or a bytes object should be really cheap, so I still don't accept this as a matter of fact situation.

Btw, going to 3.2 isn't a real option for us any time soon.  A lot of companies probably find themselves in a similar situation.  This is why I spend so much effort applying some love to 2.7.  Most of the stuff I locally do to 2.7 I then contribute to python as 3.2 patches.  Someday they'll get backported, no doubt :)

K

-----Original Message-----

From: python-dev-bounces+kristjan=ccpgames.com at python.org [mailto:python-dev-bounces+kristjan=ccpgames.com at python.org] On Behalf Of Antoine Pitrou

Sent: Wednesday, October 27, 2010 19:16

To: python-dev at python.org

Subject: Re: [Python-Dev] new buffer in python2.7

> >Here are micro-benchmarks under 3.2:

>

> > $ ./python -m timeit -s "x = b'x'*10000" "x[:100]"

> > 10000000 loops, best of 3: 0.134 usec per loop $ ./python -m timeit

> > -s "x = memoryview(b'x'*10000)" "x[:100]"

> > 10000000 loops, best of 3: 0.151 usec per loop

>

> That's weird.  The greedy slice needs two memory allocations.  One for

> the ByteArray object itself, one for its cargo.  In total, more that

> 100 bytes.  In contrast, creating the MemoryView object requires only

> one allocation of a few dozen bytes.

It's not a bytearray object, it's a bytes object. It requires only a single allocation since the data is allocated inline.

The memoryview object must also call getbuffer() again on the original object.

Regards

Antoine.

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