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Accelerate byte lookup in string with `bytealg/indexbyte` 

`bytealg/indexbyte` will use AVX or SSE instruction set, if possible,
which could accelerate `CopyStringIn` function by 28%.

In worst case(CPU doesn't support SSE), `bytealg/indexbyte`
will degenerate to traversal lookup. When dealing with
short strings, `bytealg/indexbyte` has the same performance level as
before.

Signed-off-by: Jianfeng Tan <henry.tjf@antfin.com>
Signed-off-by: Hang Su <darcy.sh@antfin.com>
This commit is contained in:
Hang Su 2019-09-18 13:35:23 +08:00
parent 28f431335b
commit d72c63664b
1 changed files with 4 additions and 4 deletions
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6
pkg/sentry/usermem/usermem.go
View File

@ -16,6 +16,7 @@
package usermem
import (
"bytes"
"errors"
"io"
"strconv"
@ -270,11 +271,10 @@ func CopyStringIn(ctx context.Context, uio IO, addr Addr, maxlen int, opts IOOpt
n, err := uio.CopyIn(ctx, addr, buf[done:done+readlen], opts)
// Look for the terminating zero byte, which may have occurred before
// hitting err.
for i, c := range buf[done : done+n] {
if c == 0 {
if i := bytes.IndexByte(buf[done:done+n], byte(0)); i >= 0 {
return stringFromImmutableBytes(buf[:done+i]), nil
}
}
done += n
if err != nil {
return stringFromImmutableBytes(buf[:done]), err