commit cd36cc0744dd695657988f15f08446dc81e16efc
author Matthias Frei <matthias.frei@inf.ethz.ch> Wed Jan 26 14:48:40 2022 +0000
committer Ian Lance Taylor <iant@golang.org> Thu Jan 27 20:02:16 2022 +0000
tree 37b170d262aed55f0261c7569c0a10e426119a11
parent 2fabfed7e28f4d92229eaadd5e9e48eeefe8fce5

internal/socket: reuse closure in Recv/SendMmsg

The closure for the callback to RawConn.Read/Write is responsible for
multiple allocations per call to RecvMmsg and SendMmsg.
The batched read and write are used primarily to avoid per-call
overhead, so any such overhead negates the advantage of using these
functions.

This change introduces a struct type holding all the variables
captured by the closure passed to RawConn.Read/Write. The struct is
reused to amortize the allocations by means of a sync.Pool.
A suitable global sync.Pool instance already existed, for buffers used
to pack mmsg headers.

This change allows to reuse all allocations in WriteBatch. In ReadBatch,
only the returned net.Addr instances still need to be allocated for each
message, which cannot be avoided without fundamental changes to the
package interface.

```
name             old time/op    new time/op    delta
UDP/Batch-1-8      5.34µs ± 1%    5.40µs ± 3%     ~     (p=0.173 n=8+10)
UDP/Batch-2-8      9.74µs ± 1%    9.24µs ± 9%   -5.21%  (p=0.035 n=9+10)
UDP/Batch-4-8      16.2µs ± 4%    16.2µs ± 1%     ~     (p=0.758 n=9+7)
UDP/Batch-8-8      30.0µs ± 4%    30.0µs ± 4%     ~     (p=0.971 n=10+10)
UDP/Batch-16-8     57.3µs ± 3%    60.9µs ±16%   +6.43%  (p=0.031 n=9+9)
UDP/Batch-32-8      115µs ± 5%     119µs ± 6%   +3.15%  (p=0.043 n=10+10)
UDP/Batch-64-8      234µs ±16%     237µs ± 4%     ~     (p=0.173 n=10+8)
UDP/Batch-128-8     447µs ± 4%     470µs ± 7%   +5.22%  (p=0.002 n=10+10)
UDP/Batch-256-8     960µs ±10%     966µs ±19%     ~     (p=0.853 n=10+10)
UDP/Batch-512-8    1.00ms ± 7%    0.99ms ± 7%     ~     (p=0.387 n=9+9)

name             old alloc/op   new alloc/op   delta
UDP/Batch-1-8        232B ± 0%       52B ± 0%  -77.59%  (p=0.000 n=10+10)
UDP/Batch-2-8        280B ± 0%      104B ± 0%  -62.86%  (p=0.000 n=10+10)
UDP/Batch-4-8        384B ± 0%      208B ± 0%  -45.83%  (p=0.000 n=10+10)
UDP/Batch-8-8        592B ± 0%      416B ± 0%  -29.73%  (p=0.000 n=10+10)
UDP/Batch-16-8     1.01kB ± 0%    0.83kB ± 0%  -17.46%  (p=0.000 n=10+10)
UDP/Batch-32-8     1.84kB ± 0%    1.66kB ± 0%   -9.57%  (p=0.002 n=8+10)
UDP/Batch-64-8     3.51kB ± 0%    3.33kB ± 0%   -5.00%  (p=0.000 n=10+8)
UDP/Batch-128-8    6.84kB ± 0%    6.66kB ± 0%   -2.57%  (p=0.001 n=7+7)
UDP/Batch-256-8    13.5kB ± 0%    13.3kB ± 0%   -1.33%  (p=0.000 n=10+10)
UDP/Batch-512-8    14.7kB ± 0%    14.5kB ± 0%   -1.19%  (p=0.000 n=8+8)

name             old allocs/op  new allocs/op  delta
UDP/Batch-1-8        8.00 ± 0%      2.00 ± 0%  -75.00%  (p=0.000 n=10+10)
UDP/Batch-2-8        10.0 ± 0%       4.0 ± 0%  -60.00%  (p=0.000 n=10+10)
UDP/Batch-4-8        14.0 ± 0%       8.0 ± 0%  -42.86%  (p=0.000 n=10+10)
UDP/Batch-8-8        22.0 ± 0%      16.0 ± 0%  -27.27%  (p=0.000 n=10+10)
UDP/Batch-16-8       38.0 ± 0%      32.0 ± 0%  -15.79%  (p=0.000 n=10+10)
UDP/Batch-32-8       70.0 ± 0%      64.0 ± 0%   -8.57%  (p=0.000 n=10+10)
UDP/Batch-64-8        134 ± 0%       128 ± 0%   -4.48%  (p=0.000 n=10+10)
UDP/Batch-128-8       262 ± 0%       256 ± 0%   -2.29%  (p=0.000 n=10+10)
UDP/Batch-256-8       518 ± 0%       512 ± 0%   -1.16%  (p=0.000 n=10+10)
UDP/Batch-512-8       562 ± 0%       556 ± 0%   -1.07%  (p=0.000 n=10+10)
```

Contributes to golang/go#26838

Change-Id: I16ecfc38dbb5a4d9b1ceacd1dd99fda38f346807
GitHub-Last-Rev: d1dda931f61bd08cab782fa50406574d5e227154
GitHub-Pull-Request: golang/net#126
Reviewed-on: https://go-review.googlesource.com/c/net/+/380934
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Michael Knyszek <mknyszek@google.com>