doumei1926
2016-05-28 15:35
浏览 169

具有相同golang代码段的巨大性能差异查询mysql数据库

I reimplement my project with golang recently. The project was implemented with C++. When I finished the code and have a performance test. I'm shocked by the result. When I query the database with C++, I can get the 130 million rows result in 5 mins. But with golang, it's almost 45 mins. But when I separate the code from the project and build the code snippet, it's finished in 2mins. Why does they have so much huge difference performance result?

My code snippet : https://gist.github.com/pyanfield/2651d23311901b33c5723b7de2364148

package main

import (
    "database/sql"
    "fmt"
    "runtime"
    "strconv"
    "time"

    _ "github.com/go-sql-driver/mysql"
)

func main() {
    runtime.GOMAXPROCS(runtime.NumCPU())
    // defer profile.Start(profile.CPUProfile, profile.ProfilePath(".")).Stop()
    dbRead, err := connectDB("test:test@tcp(127.0.0.1:3306)/test_oltp?charset=utf8&readTimeout=600s&writeTimeout=600s")
    if err != nil {
        fmt.Printf("Error happend when connecting to DB. %s
", err.Error())
        return
    }
    defer dbRead.Close()
    dbRead.SetMaxIdleConns(0)
    dbRead.SetMaxOpenConns(100)

    query := fmt.Sprintf("WHERE company_id in (11,22,33,44,55,66,77,88,99,00,111,222,333,4444,555,666,777,888,999)")

    relations := getRelations(dbRead, query)
}
func connectDB(addr string) (*sql.DB, error) {
    db, err := sql.Open("mysql", addr)
    if err != nil {
        return nil, err
    }
    if err = db.Ping(); err != nil {
        return nil, err
    }
    return db, nil
}

type Relation struct {
    childId  int64 
    parentId int64 
}

func getRelations(db *sql.DB, where string)[]Relation {
    begin := time.Now()

    var err error
    var rows *sql.Rows
    query := fmt.Sprintf("SELECT `child_id`, `parent_id` FROM `test_relations` %s", where)
    rows, err = db.Query(query)
    if err != nil {
        fmt.Println("query error:", err.Error())
        return nil
    }
    defer rows.Close()

    columns, err := rows.Columns()
    buffer := make([]sql.RawBytes, len(columns))
    scanArgs := make([]interface{}, len(buffer))
    for i := range scanArgs {
        scanArgs[i] = &buffer[i]
    }

    relations := []Relation{}
    relation := Relation{}
    for rows.Next() {
        if err = rows.Scan(scanArgs...); err != nil {
            fmt.Println("scan:", err.Error())
            return nil
        }
        relation.parentId, _ = strconv.ParseInt(string(buffer[1]), 10, 64)
        relation.childId, _ = strconv.ParseInt(string(buffer[0]), 10, 64)

        relations = append(relations, relation)
    }

    if err = rows.Err(); err != nil {
        fmt.Println("next error:", err.Error())
        return nil
    }
    fmt.Printf(">>> getRelations cost: %s
", time.Since(begin).String())
    // output :>>> getRelations cost:1m45.791047s
    return relations
    // len(relations): 131123541
}

Update: My go version is 1.6. The cpu profile I got are as below: The Code Snippet profile top20:

    75.67s of 96.82s total (78.16%)
Dropped 109 nodes (cum <= 0.48s)
Showing top 20 nodes out of 82 (cum >= 12.04s)
      flat  flat%   sum%        cum   cum%
    11.85s 12.24% 12.24%     11.85s 12.24%  runtime.memmove
    10.28s 10.62% 22.86%     20.01s 20.67%  runtime.mallocgc
     5.82s  6.01% 28.87%      5.82s  6.01%  strconv.ParseUint
     5.79s  5.98% 34.85%      5.79s  5.98%  runtime.futex
     3.42s  3.53% 38.38%     10.28s 10.62%  github.com/go-sql-driver/mysql.(*buffer).readNext
     3.42s  3.53% 41.91%      6.38s  6.59%  runtime.scang
     3.37s  3.48% 45.39%     36.97s 38.18%  github.com/go-sql-driver/mysql.(*textRows).readRow
     3.37s  3.48% 48.87%      3.37s  3.48%  runtime.memclr
     3.20s  3.31% 52.18%      3.20s  3.31%  runtime.heapBitsSetType
     3.02s  3.12% 55.30%      7.36s  7.60%  database/sql.convertAssign
     2.96s  3.06% 58.36%      3.02s  3.12%  runtime.(*mspan).sweep.func1
     2.53s  2.61% 60.97%      2.53s  2.61%  runtime._ExternalCode
     2.39s  2.47% 63.44%      2.96s  3.06%  runtime.readgstatus
     2.24s  2.31% 65.75%      8.06s  8.32%  strconv.ParseInt
     2.21s  2.28% 68.03%      5.24s  5.41%  runtime.heapBitsSweepSpan
     2.15s  2.22% 70.25%      7.68s  7.93%  runtime.rawstring
     2.06s  2.13% 72.38%      3.18s  3.28%  github.com/go-sql-driver/mysql.readLengthEncodedString
     1.95s  2.01% 74.40%     12.23s 12.63%  github.com/go-sql-driver/mysql.(*mysqlConn).readPacket
     1.83s  1.89% 76.29%     79.42s 82.03%  main.Relations
     1.81s  1.87% 78.16%     12.04s 12.44%  runtime.slicebytetostring

The project cpu profile top20:

     (pprof) top20
38.71mins of 42.82mins total (90.40%)
Dropped 334 nodes (cum <= 0.21mins)
Showing top 20 nodes out of 76 (cum >= 1.35mins)
      flat  flat%   sum%        cum   cum%
 12.02mins 28.07% 28.07%  12.48mins 29.15%  runtime.addspecial
  5.95mins 13.89% 41.96%  15.08mins 35.21%  runtime.pcvalue
  5.26mins 12.29% 54.25%   5.26mins 12.29%  runtime.readvarint
  2.60mins  6.08% 60.32%   7.87mins 18.37%  runtime.step
  1.98mins  4.62% 64.94%  19.45mins 45.43%  runtime.gentraceback
  1.65mins  3.86% 68.80%   1.65mins  3.86%  runtime/internal/atomic.Xchg
  1.57mins  3.66% 72.46%   2.93mins  6.84%  runtime.(*mspan).sweep
  1.52mins  3.54% 76.01%   1.78mins  4.15%  runtime.findfunc
  1.41mins  3.30% 79.31%   1.42mins  3.31%  runtime.markrootSpans
  1.13mins  2.64% 81.95%   1.13mins  2.64%  runtime.(*fixalloc).alloc
  0.64mins  1.50% 83.45%   0.64mins  1.50%  runtime.duffcopy
  0.46mins  1.08% 84.53%   0.46mins  1.08%  runtime.findmoduledatap
  0.44mins  1.02% 85.55%   0.44mins  1.02%  runtime.fastrand1
  0.42mins  0.97% 86.52%  15.49mins 36.18%  runtime.funcspdelta
  0.38mins  0.89% 87.41%  36.02mins 84.13%  runtime.mallocgc
  0.30mins   0.7% 88.12%   0.78mins  1.83%  runtime.scanobject
  0.26mins   0.6% 88.72%   0.32mins  0.74%  runtime.stkbucket
  0.26mins   0.6% 89.32%   0.26mins   0.6%  runtime.memmove
  0.23mins  0.55% 89.86%   0.23mins  0.55%  runtime.heapBitsForObject
  0.23mins  0.53% 90.40%   1.35mins  3.15%  runtime.lock
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2条回答 默认 最新

  • donkey111111 2016-06-01 02:12
    已采纳

    I got my answer and want to share it. This is caused by my mistake. Sometimes ago, I tried to add memory profile and set runtime. MemProfileRate=1 in my init method. But I forgot to reset it to a reasonable value. I ignored this method when I checked my code every time. After removing this setting from my project, it returns to normal, and spend almost 5~6mins to query these 130M datas. The speed is pretty close to the C++ version. My advise is that please carefully when you set runtime.MemProfileRate=1 unless you make sure you want to do that, and remember to reset it back.

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  • dongping2023 2016-05-28 15:50

    Golang is likely running the DB query processing more in parallel for the snippet alone. Your complete application is almost certainly using some of those cores for other things.

    The loop where you process all 130M rows seems the likely culprit.

    Try setting the max procs to 1 in the snippet if you want to test this theory.

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