commit	a34f42077461688bb5e1318e4e04d20c91f1ab8a	[log] [tgz]
author	David Taylor <tinystatemachine@gmail.com>	Mon Jan 17 21:54:17 2022 +0000
committer	Alex Rakoczy <alex@golang.org>	Fri May 27 14:59:08 2022 +0000
tree	0ec637f183a71e1e969261959940e17763443919
parent	c838098c327a1b6d63446f4722e943b02d235d78 [diff]

[release-branch.go1.18] crypto/tls: avoid extra allocations in steady-state Handshake calls

The Read and Write methods of *tls.Conn call Handshake
unconditionally, every time they are called, expecting it to only
perform a new handshake if required.

However in go 1.17 handshakeContext was extended to set up a
cancelable Context, and importantly did so prior to checking if a
handshake is required. This thus causes it to allocate on every call,
even in those that are no-ops when called in a Read or Write on an
established connection, sometimes leading to very large numbers of
allocations during reads.

This change adds an early return, prior to setting up the context or
proceeding into the handshakeMutex and checking the handshake error, if
the handshake status atomic indicates handshake is already complete.

name                                     old allocs/op  new allocs/op  delta
Throughput/MaxPacket/1MB/TLSv12-10          1.07k ± 0%     0.62k ± 0%  -42.16%  (p=0.000 n=4+5)
Throughput/MaxPacket/1MB/TLSv13-10          1.70k ± 0%     1.25k ± 0%     ~     (p=0.079 n=4+5)
Throughput/MaxPacket/2MB/TLSv12-10          1.62k ± 0%     0.73k ± 0%  -55.18%  (p=0.008 n=5+5)
Throughput/MaxPacket/2MB/TLSv13-10          2.26k ± 0%     1.36k ± 0%  -39.64%  (p=0.008 n=5+5)
Throughput/MaxPacket/4MB/TLSv12-10          2.74k ± 0%     0.95k ± 0%  -65.35%  (p=0.008 n=5+5)
Throughput/MaxPacket/4MB/TLSv13-10          3.37k ± 0%     1.58k ± 0%  -53.15%  (p=0.008 n=5+5)
Throughput/MaxPacket/8MB/TLSv12-10          4.96k ± 0%     1.39k ± 0%  -72.06%  (p=0.016 n=4+5)
Throughput/MaxPacket/8MB/TLSv13-10          5.60k ± 0%     2.01k ± 0%  -64.05%  (p=0.008 n=5+5)
Throughput/MaxPacket/16MB/TLSv12-10         9.42k ± 0%     2.27k ± 1%  -75.92%  (p=0.016 n=4+5)
Throughput/MaxPacket/16MB/TLSv13-10         10.0k ± 0%      2.9k ± 0%  -71.39%  (p=0.008 n=5+5)
Throughput/MaxPacket/32MB/TLSv12-10         18.3k ± 0%      4.0k ± 0%  -77.97%  (p=0.008 n=5+5)
Throughput/MaxPacket/32MB/TLSv13-10         18.9k ± 0%      4.6k ± 0%  -75.62%  (p=0.008 n=5+5)
Throughput/MaxPacket/64MB/TLSv12-10         36.2k ± 0%      7.5k ± 0%  -79.15%  (p=0.008 n=5+5)
Throughput/MaxPacket/64MB/TLSv13-10         36.7k ± 0%      8.1k ± 0%  -78.06%  (p=0.008 n=5+5)
Throughput/DynamicPacket/1MB/TLSv12-10      1.12k ± 0%     0.63k ± 0%  -44.20%  (p=0.008 n=5+5)
Throughput/DynamicPacket/1MB/TLSv13-10      1.76k ± 0%     1.26k ± 0%  -28.22%  (p=0.016 n=5+4)
Throughput/DynamicPacket/2MB/TLSv12-10      1.68k ± 0%     0.74k ± 0%  -56.11%  (p=0.008 n=5+5)
Throughput/DynamicPacket/2MB/TLSv13-10      2.32k ± 0%     1.37k ± 0%  -40.80%  (p=0.008 n=5+5)
Throughput/DynamicPacket/4MB/TLSv12-10      2.80k ± 0%     0.96k ± 0%  -65.81%  (p=0.008 n=5+5)
Throughput/DynamicPacket/4MB/TLSv13-10      3.43k ± 0%     1.59k ± 0%  -53.57%  (p=0.008 n=5+5)
Throughput/DynamicPacket/8MB/TLSv12-10      5.03k ± 0%     1.39k ± 0%  -72.27%  (p=0.008 n=5+5)
Throughput/DynamicPacket/8MB/TLSv13-10      5.66k ± 0%     2.02k ± 0%  -64.27%  (p=0.008 n=5+5)
Throughput/DynamicPacket/16MB/TLSv12-10     9.48k ± 0%     2.28k ± 1%  -75.98%  (p=0.008 n=5+5)
Throughput/DynamicPacket/16MB/TLSv13-10     10.1k ± 0%      2.9k ± 0%  -71.34%  (p=0.008 n=5+5)
Throughput/DynamicPacket/32MB/TLSv12-10     18.4k ± 0%      4.0k ± 0%  -78.13%  (p=0.008 n=5+5)
Throughput/DynamicPacket/32MB/TLSv13-10     19.0k ± 0%      4.6k ± 0%  -75.54%  (p=0.008 n=5+5)
Throughput/DynamicPacket/64MB/TLSv12-10     36.2k ± 0%      7.6k ± 1%  -79.02%  (p=0.008 n=5+5)
Throughput/DynamicPacket/64MB/TLSv13-10     36.8k ± 0%      8.2k ± 1%  -77.76%  (p=0.008 n=5+5)

Fixes #52791

Change-Id: Iacb1f9bf7802022960d9dbce141b8c0587a614d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/379034
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <valsorda@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org>
(cherry picked from commit a4af35607536b2b0d73be94df188b9f5a157480c)
Reviewed-on: https://go-review.googlesource.com/c/go/+/405545
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Alex Rakoczy <alex@golang.org>

src/crypto/tls/conn.go[diff]

1 file changed

tree: 0ec637f183a71e1e969261959940e17763443919

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