Avoid many temporary allocations when serializing service protocol responses

Avoid many temporary allocations when serializing service protocol responses

- [x] Use an on stack buffer for small string allocations.
- [x] Avoid unnecessary calls to strlen.

Related #29207

BUG=
R=rmacnak@google.com, zra@google.com

Committed: https://github.com/dart-lang/sdk/commit/904beb3d9d2e86ffcf933fd5076a0979af1dba47

[Cutch, 2017-03-31 17:38:56]

Description was changed from

==========
Avoid many temporary allocations when serializing service protocol responses

- [x] Use an on stack buffer for small string allocations.
- [x] Avoid unnecessary calls to strlen.

Related #29207

BUG=
==========

to

==========
Avoid many temporary allocations when serializing service protocol responses

- [x] Use an on stack buffer for small string allocations.
- [x] Avoid unnecessary calls to strlen.

Related #29207

BUG=
==========

[Cutch, 2017-03-31 17:38:57]

johnmccutchan@google.com changed reviewers:
+ cbracken@google.com, rmacnak@google.com, zra@google.com

[zra, 2017-03-31 17:47:09]

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc
File runtime/vm/json_stream.cc (right):

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc#n...
runtime/vm/json_stream.cc:493: const intptr_t kOnStackBufferCapacity = 4096;
Maybe something like:

class MaybeOnStackBuffer {
 public:
  MaybeOnStackBuffer(intptr_t size) {
    if (size > kOnStackBufferCapacity) {
      p_ = malloc(size);
    } else {
      p_ = &buffer_[0];
    }
  }
  ~MaybeOnStackBuffer() {
    if (p_ != &buffer_[0]) free(p_);
  }

  char* p() { return p_; }

 private:
  char* p_;
  char buffer_[kOnStackBufferCapacity];
}

[siva, 2017-03-31 17:59:32]

asiva@google.com changed reviewers:
+ asiva@google.com

[siva, 2017-03-31 17:59:33]

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc
File runtime/vm/json_stream.cc (right):

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc#n...
runtime/vm/json_stream.cc:502: if (len + 1 >= kOnStackBufferCapacity) {
((len + 1) >= kOnStackBufferCapacity) here and below.

[Cutch, 2017-03-31 18:04:47]

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc
File runtime/vm/json_stream.cc (right):

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc#n...
runtime/vm/json_stream.cc:493: const intptr_t kOnStackBufferCapacity = 4096;
On 2017/03/31 17:47:09, zra wrote:
> Maybe something like:
> 
> class MaybeOnStackBuffer {
>  public:
>   MaybeOnStackBuffer(intptr_t size) {
>     if (size > kOnStackBufferCapacity) {
>       p_ = malloc(size);
>     } else {
>       p_ = &buffer_[0];
>     }
>   }
>   ~MaybeOnStackBuffer() {
>     if (p_ != &buffer_[0]) free(p_);
>   }
> 
>   char* p() { return p_; }
> 
>  private:
>   char* p_;
>   char buffer_[kOnStackBufferCapacity];
> }

Done.

https://codereview.chromium.org/2791633002/diff/1/runtime/vm/json_stream.cc#n...
runtime/vm/json_stream.cc:502: if (len + 1 >= kOnStackBufferCapacity) {
On 2017/03/31 17:59:33, siva wrote:
> ((len + 1) >= kOnStackBufferCapacity) here and below.

Acknowledged.

[rmacnak, 2017-03-31 18:08:30]

lgtm

[zra, 2017-03-31 18:13:18]

lgtm

[Cutch, 2017-03-31 20:20:17]

Description was changed from

==========
Avoid many temporary allocations when serializing service protocol responses

- [x] Use an on stack buffer for small string allocations.
- [x] Avoid unnecessary calls to strlen.

Related #29207

BUG=
==========

to

==========
Avoid many temporary allocations when serializing service protocol responses

- [x] Use an on stack buffer for small string allocations.
- [x] Avoid unnecessary calls to strlen.

Related #29207

BUG=
R=rmacnak@google.com, zra@google.com

Committed:
https://github.com/dart-lang/sdk/commit/904beb3d9d2e86ffcf933fd5076a0979af1dba47
==========

[Cutch, 2017-03-31 20:20:18]

Committed patchset #2 (id:20001) manually as
904beb3d9d2e86ffcf933fd5076a0979af1dba47 (presubmit successful).