mirror of
https://github.com/tailscale/tailscale.git
synced 2026-09-15 15:29:33 -04:00
James Tucker
0d66cde14f
Static size checks (iossize) catch binary dirty-page growth but nothing covered runtime heap cost, which is what actually consumes the iOS Network Extension's 50 MiB jetsam budget. Bring up a tsnet backend (with the full condregister feature set, matching shipping clients) against an in-process testcontrol server and assert live post-GC heap budgets for (a) backend startup with zero peers and (b) marginal cost per netmap peer. The startup test measures 1.3 MiB today and fails loudly on the conn25 flow-table pre-allocation regression (17 MiB) that jetsam-killed the iOS extension on large tailnets. Budgets are deliberately generous (6-12x current measurements) to stay flake-free while still catching the multi-MiB regressions that matter for mobile. A new debugknob enables us to constrain the GSO/GRO batch size to 1 for these tests so as to avoid the memory allocation associated with those buffers, which are a known issue with their own work stream. Updates tailscale/corp#46408 Updates tailscale/corp#18514 Signed-off-by: James Tucker <james@tailscale.com>
75 lines
3.0 KiB
Go
75 lines
3.0 KiB
Go
// Copyright (c) Tailscale Inc & contributors
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// SPDX-License-Identifier: BSD-3-Clause
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// Package batching implements a socket optimized for increased throughput.
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package batching
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import (
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"net/netip"
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"golang.org/x/net/ipv4"
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"golang.org/x/net/ipv6"
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"tailscale.com/envknob"
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"tailscale.com/net/packet"
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"tailscale.com/types/nettype"
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)
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// BatchSizeFromEnv returns ideal, unless the TS_DEBUG_WG_BATCH_SIZE
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// environment variable is set to a positive integer, in which case it returns
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// that value clamped to [1, ideal].
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//
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// Batch size determines how much packet memory wireguard-go pins per reader
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// goroutine (batch size × 64 KiB message buffers per reader, ~32 MiB total at
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// the Linux default of 128), so memory-budget tests set the env var to 1 to
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// approximate the configuration used on memory-constrained (mobile)
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// platforms, where batch size is always 1.
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func BatchSizeFromEnv(ideal int) int {
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if v, ok := envknob.LookupInt("TS_DEBUG_WG_BATCH_SIZE"); ok && v > 0 {
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return min(v, ideal)
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}
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return ideal
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}
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var (
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// This acts as a compile-time check for our usage of ipv6.Message in
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// [Conn] for both IPv6 and IPv4 operations.
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_ ipv6.Message = ipv4.Message{}
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)
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// Conn is a [nettype.PacketConn] that provides batched i/o using
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// platform-specific optimizations, e.g. {recv,send}mmsg & UDP GSO/GRO.
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//
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// Conn does not support single packet reads (see ReadFromUDPAddrPort docs). It
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// is the caller's responsibility to use the appropriate read API where a
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// [nettype.PacketConn] has been upgraded to support batched i/o.
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//
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// Conn originated from (and is still used by) magicsock where its API was
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// strongly influenced by [wireguard-go/conn.Bind] constraints, namely
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// wireguard-go's ownership of packet memory.
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type Conn interface {
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nettype.PacketConn
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// ReadFromUDPAddrPort always returns an error, as UDP GRO is incompatible
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// with single packet reads. A single datagram may be multiple, coalesced
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// datagrams, and this API lacks the ability to pass that context.
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//
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// TODO: consider detaching Conn from [nettype.PacketConn]
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ReadFromUDPAddrPort([]byte) (int, netip.AddrPort, error)
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// ReadBatch reads messages from [Conn] into msgs. It returns the number of
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// messages the caller should evaluate for nonzero len, as a zero len
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// message may fall on either side of a nonzero.
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//
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// Each [ipv6.Message.OOB] must be sized to at least MinControlMessageSize().
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ReadBatch(msgs []ipv6.Message, flags int) (n int, err error)
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// WriteBatchTo writes buffs to addr.
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//
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// If geneve.VNI.IsSet(), then geneve is encoded into the space preceding
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// offset, and offset must equal [packet.GeneveFixedHeaderLength]. If
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// !geneve.VNI.IsSet() then the space preceding offset is ignored.
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//
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// len(buffs) must be <= batchSize supplied in TryUpgradeToConn().
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//
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// WriteBatchTo may return a [neterror.ErrUDPGSODisabled] error if UDP GSO
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// was disabled as a result of a send error.
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WriteBatchTo(buffs [][]byte, addr netip.AddrPort, geneve packet.GeneveHeader, offset int) error
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}
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