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Published byJocelyn Kennedy Modified 5年之前
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Python memory management & Impact to memory-hungry application
Kilik Kuo
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Outline About Photo-Organizing Software
What is it ? Who use it ? Problems to developers Brief to Python memory management Thank God, we have Evan Jones & Nice guy Tim Peter Possible solutions ? For those which are handled in Python For those can't be handled in Python
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About Photo-Organizing Software
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About Photo-Organizing Software
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About Photo-Organizing Software
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About Photo-Organizing Software
Problems that may kill the engineer ! Rapid UI flow experience Full metadata display Fancy UI transformation Handle higher resolution 24 million (6000x4000) pixels 48 million (8000x6000) pixels ... WTF
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Metadata - EXIF/ IPTC/ XMP...
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Houston, we've got a Problem !!
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Hungry for Memory Space !!!
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Let's explore the SPACE 8000(W) x 6000(H) x 4(RGBA) x 2(BytePerChannel) = 366 MB Space Start Space End Heap
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Does it work on PhD ? Continuous Memory Address is the KEY !!
1 BIG image should be ok, then 2, 3, 4, ... ? On 32-bit OS Limited to 2G user-mode virtual space per process Windows ASLR (Blue part - dll Image) 0x <-> 0x 0x <-> 0x 0x > You get almost 1G continuous memory space, until Python occupy the RED, and won't return to OS. On 64-bit OS 8TB user-mode by default Physical memory size is what you need to concern. 0x
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Python Memory Management
Imagine there's a PyBank, and you wanna get mortgage Trick or Treat ...... $240, please ~ sure !
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PMM - Allocator 四大天王 /trunk/Objects/obmalloc.c
PyObject_New/PyObject_Del
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Inside the PyBank - PyObject Allocator
儲櫃 Free 1 255 110 14 26萬2144元 滿抽屜 4096元 262,144 / 4096 = 64 110 110 110 110 4096元 抽屜 14 14 錢袋 14 14 4096元
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PyBank Money Management
蟒銀存款 : 21億4748萬3648元 小額放款部 (< 256 元) 大額放款部 (> 256 元) 取款步驟 告知銀行, 大額 or 小額 - 兜幾 ? 小額 檢查(放款儲櫃中的特定抽屜)裡找尋是否有剩餘符合的指定金額錢 袋 有, 從剩餘的指定金額錢袋中拿一袋給你 沒有 從(錢最少但還有滿抽屜的儲櫃)中的滿抽屜裡拿出指定金 額的錢袋 沒有儲櫃 開新的放款儲櫃, 從一個滿抽屜拿一袋指定金額錢袋 給你 大額 拿去拿去拿去 ~ 怎決定的 ?
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儲櫃 Arena /抽屜 Pool /錢袋 Block
Free 7 110 144 2 43 5 3 13 8 64 1 255 14 23 Free Pool(滿抽屜) Free Pool 26萬2144元 A1 A0 A2 A3 Partially allocated Arena list 1 - 8 Byte Byte Byte Pool(非滿抽屜) - A2 Pool(非滿抽屜) - A0 A2 2 1 5 Used Pool list & Free Block list
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Release the memory All used Blocks(from Pool A) return to Pool A, and all used Pools(from Arena B) return to Arena B Arena B is freed ! After Python 2.3 (Evan Jones & Nice guy Tim Peter) Something still weird ... int / float / tuple / list / dict doesn't act like above gg...
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Back to IMPACT - Solutions ?
What can we do ? First, know where we are ! EXE 1. include "Python.h" 2. Load Python2X.dll 3. Py_Initialze() 4. Load script & DeMarshal it as PyCodeobject 5. PyEval_EvalCode(PyCodeObject) Python Interpreter 1. int, float, list, tup, dict 2. PyObjects 3. Others SWIG 1. malloc, new ... 2. Create PyObjects 3. Others
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Inside Python World For list/ dict objects
gc.collect() is able to release the maintained free list for list/ dict Don't call it in the function where large list/dict items being created. Use subprocess to hold these objects, and retrieve information through IPC. Wrap the creation of these objects down to SWIG.
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Outside Python World
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Outside Python World (Cont.)
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Outside Python World (Cont.)
Divide image raw data into chunks Re-write all related functions Decode/ Stretch/ Encode/ Rotate Pixel Operation, eg. BGRA <-> RGB. Color Management Retouch/Edit effect algorithm 族繁不及備載, 臨表涕泣, 不知所云... Performance ? SIMD Multi-threaded (OpenMP) Be aware of thread context switch overhead GPU (OpenCL ?)
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Conclusion Be an open-minded engineer !!
You're more powerful than you think you are.
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Q & A
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