2020. március 26., csütörtök 7:58:59 UTC+1 időpontban steve tang a
következőt írta:
>
> Thanks, I used sync.Pool to allocate a byte.Buffer, and response.Body
> isn't constant size in program, I find golang will grow the byte.Buffer
> space against to initial space. I changed code as follows:
>
> type SyncPool struct{ Pool sync.Pool }
>
> func (s *SyncPool) Get(n int) []byte {
> //比n大，不需要slice增长时，使用buffer pool
> if b, ok := s.Pool.Get().([]byte); ok && cap(b) >= n {
> return b[:n]
> } else {
> //miss size
> s.Put(b)
> return make([]byte, n)
> }
> }
>
> func (s *SyncPool) Put(b []byte) {
> s.Pool.Put(b)
> }
>
>
>
> const FourMB = 4 * 1024 * 1024
>
> var pool = &SyncPool{
> sync.Pool{
> New: func() interface{} {
> return make([]byte, FourMB)
> },
> },
> }
>
>
>
>
> On Thursday, March 26, 2020 at 12:22:01 PM UTC+8, robert engels wrote:
>>
>> If the pool is a sync.Pool:
>>
>> Any item stored in the Pool may be removed automatically at any time without
>> 18 // notification. If the Pool holds the only reference when this
>> happens, the 19 // item might be deallocated.
>>
>> So placing an object in the pool does not guarantee it won’t be collected
>> - causing a future allocation.
>>
>> On Mar 25, 2020, at 10:22 PM, steve tang <tsg...@gmail.com> wrote:
>>
>> chunkCrc32Hash := crc32.NewIEEE()
>> chunkBuf := bufferpool.GetInstance().Get()
>> //回收buffer
>> defer bufferpool.GetInstance().Put(chunkBuf)
>> writer := io.MultiWriter(chunkBuf, chunkCrc32Hash)
>> _, copyErr := io.Copy(writer, chunkResp.RawResponse.Body)
>> if copyErr != nil && copyErr != io.EOF {
>> logmgr.ErrorLogger(ctx, "fail to write chunk data to crc32 or buffer,
>> req: %s, err: %s", originReq.PrettyPrint(), copyErr)
>> return false, exception.OEFException(nil,
>> http.StatusInternalServerError, CopyChunkError, "internal server exception")
>> }
>>
>> In above codes, it writes chunk data to buffer pool, and the chunk data
>> size is 4MB. When I used golang tool pprof to export memory pprof, there
>> about 8MB space has been allocated. Could somebody help me why golang
>> allocated
>> memory space increases?
>>
>>
>> <20200326-111844.png>
>>
>>
>>
>>
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>> .
>> <20200326-111844.png>
>>
>>
>>
1. sync.Pool MUST use pointers (*[]byte)
2. what is `chunkBuf := bufferpool.GetInstance().Get()` ? it must be an
io.Writer, but you should Reset/Truncate it when you Put it back to the
pool!
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