From a3a63c082d896e8ae6d0f6295b3a7e8176dbd41c Mon Sep 17 00:00:00 2001
From: Robert Collins <robertc@robertcollins.net>
Date: Sat, 22 Feb 2020 15:47:07 +1300
Subject: [PATCH] Fix #2229 detect available memory

This doesn't implement streaming IO for low memory situations - we still
have the situation that low footprint situations will fail to install,
but while it is the case that rustc's memory footprint is lower than our
unpack footprint this is probably not urgent to fix, though I will get
around to it.

Being less aggressive about unpack buffer size though should reduce the
number of support tickets from folk in these cases, I hope.

We may end up getting tickets from folk with broken ulimit syscalls
though, who knows.
---
 Cargo.lock                    | 99 ++++++++++++++++++++++-------------
 Cargo.toml                    |  1 +
 src/dist/component/package.rs | 45 ++++++++++++----
 src/errors.rs                 |  1 +
 tests/cli-exact.rs            |  3 ++
 tests/cli-rustup.rs           |  5 ++
 tests/cli-self-upd.rs         |  1 +
 tests/cli-v2.rs               |  1 +
 8 files changed, 111 insertions(+), 45 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index a7363a44319..1e00a29762f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -72,7 +72,7 @@ name = "atty"
 version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -88,7 +88,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "backtrace-sys 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -98,7 +98,7 @@ version = "0.1.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -233,7 +233,7 @@ name = "chrono"
 version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-integer 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -272,7 +272,7 @@ version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "core-foundation-sys 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -299,7 +299,7 @@ version = "0.4.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "curl-sys 0.4.23 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-probe 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.52 (registry+https://github.com/rust-lang/crates.io-index)",
  "schannel 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -313,7 +313,7 @@ version = "0.4.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.52 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -412,7 +412,7 @@ version = "0.6.5"
 dependencies = [
  "curl 0.4.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_proxy 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "error-chain 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "error-chain 0.12.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "reqwest 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -437,6 +437,17 @@ dependencies = [
  "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "effective-limits"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "error-chain 0.12.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sys-info 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.20"
@@ -456,11 +467,11 @@ dependencies = [
 
 [[package]]
 name = "error-chain"
-version = "0.12.1"
+version = "0.12.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "backtrace 0.3.40 (registry+https://github.com/rust-lang/crates.io-index)",
- "version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -494,7 +505,7 @@ version = "0.2.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -506,7 +517,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "crc32fast 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "miniz_oxide 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -597,7 +608,7 @@ version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasi 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -746,7 +757,7 @@ name = "iovec"
 version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -786,7 +797,7 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.65"
+version = "0.2.67"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -800,7 +811,7 @@ version = "1.0.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "vcpkg 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -819,7 +830,7 @@ version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -875,7 +886,7 @@ dependencies = [
  "fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "iovec 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "miow 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "net2 0.2.33 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -900,7 +911,7 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl 0.10.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-probe 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -917,7 +928,7 @@ version = "0.2.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -990,7 +1001,7 @@ name = "num_cpus"
 version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1015,7 +1026,7 @@ dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "foreign-types 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.52 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1039,7 +1050,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-src 111.6.0+1.1.1d (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "vcpkg 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1167,7 +1178,7 @@ version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "getrandom 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_chacha 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1320,12 +1331,13 @@ dependencies = [
  "chrono 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "download 0.6.5",
- "error-chain 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "effective-limits 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "error-chain 0.12.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "flate2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "git-testament 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "home 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "opener 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl 0.10.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "pgp 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1392,7 +1404,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "core-foundation 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation-sys 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "security-framework-sys 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1493,7 +1505,7 @@ version = "0.3.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1552,13 +1564,22 @@ dependencies = [
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "sys-info"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cc 1.0.46 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "tar"
 version = "0.4.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "filetime 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "xattr 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1569,7 +1590,7 @@ version = "3.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "remove_dir_all 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1614,7 +1635,7 @@ name = "time"
 version = "0.1.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1761,12 +1782,17 @@ name = "version_check"
 version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "version_check"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "wait-timeout"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1959,7 +1985,7 @@ name = "xattr"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2040,9 +2066,10 @@ dependencies = [
 "checksum digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f3d0c8c8752312f9713efd397ff63acb9f85585afbf179282e720e7704954dd5"
 "checksum dtoa 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "ea57b42383d091c85abcc2706240b94ab2a8fa1fc81c10ff23c4de06e2a90b5e"
 "checksum ed25519-dalek 1.0.0-pre.3 (registry+https://github.com/rust-lang/crates.io-index)" = "978710b352437433c97b2bff193f2fb1dfd58a093f863dd95e225a19baa599a2"
+"checksum effective-limits 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0a9f83f5e74da97619a9c13722c22609ab82ee797a2d9985b2b3405c69f03cd7"
 "checksum encoding_rs 0.8.20 (registry+https://github.com/rust-lang/crates.io-index)" = "87240518927716f79692c2ed85bfe6e98196d18c6401ec75355760233a7e12e9"
 "checksum env_proxy 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8731da06ff3731a69115a2910345ae5ee8d1fe09c846a9eca101b444a30ad454"
-"checksum error-chain 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3ab49e9dcb602294bc42f9a7dfc9bc6e936fca4418ea300dbfb84fe16de0b7d9"
+"checksum error-chain 0.12.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d371106cc88ffdfb1eabd7111e432da544f16f3e2d7bf1dfe8bf575f1df045cd"
 "checksum failure 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "f8273f13c977665c5db7eb2b99ae520952fe5ac831ae4cd09d80c4c7042b5ed9"
 "checksum failure_derive 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "0bc225b78e0391e4b8683440bf2e63c2deeeb2ce5189eab46e2b68c6d3725d08"
 "checksum fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e88a8acf291dafb59c2d96e8f59828f3838bb1a70398823ade51a84de6a6deed"
@@ -2081,7 +2108,7 @@ dependencies = [
 "checksum keccak 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "67c21572b4949434e4fc1e1978b99c5f77064153c59d998bf13ecd96fb5ecba7"
 "checksum kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
 "checksum lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
-"checksum libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)" = "1a31a0627fdf1f6a39ec0dd577e101440b7db22672c0901fe00a9a6fbb5c24e8"
+"checksum libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)" = "eb147597cdf94ed43ab7a9038716637d2d1bf2bc571da995d0028dec06bd3018"
 "checksum libm 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c7d73b3f436185384286bd8098d17ec07c9a7d2388a6599f824d8502b529702a"
 "checksum libz-sys 1.0.25 (registry+https://github.com/rust-lang/crates.io-index)" = "2eb5e43362e38e2bca2fd5f5134c4d4564a23a5c28e9b95411652021a8675ebe"
 "checksum log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)" = "14b6052be84e6b71ab17edffc2eeabf5c2c3ae1fdb464aae35ac50c67a44e1f7"
@@ -2160,6 +2187,7 @@ dependencies = [
 "checksum subtle 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ab3af2eb31c42e8f0ccf43548232556c42737e01a96db6e1777b0be108e79799"
 "checksum syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "66850e97125af79138385e9b88339cbcd037e3f28ceab8c5ad98e64f0f1f80bf"
 "checksum synstructure 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3f085a5855930c0441ca1288cf044ea4aecf4f43a91668abdb870b4ba546a203"
+"checksum sys-info 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)" = "0079fe39cec2c8215e21b0bc4ccec9031004c160b88358f531b601e96b77f0df"
 "checksum tar 0.4.26 (registry+https://github.com/rust-lang/crates.io-index)" = "b3196bfbffbba3e57481b6ea32249fbaf590396a52505a2615adbb79d9d826d3"
 "checksum tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
 "checksum term 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5e6b677dd1e8214ea1ef4297f85dbcbed8e8cdddb561040cc998ca2551c37561"
@@ -2186,6 +2214,7 @@ dependencies = [
 "checksum vcpkg 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)" = "33dd455d0f96e90a75803cfeb7f948768c08d70a6de9a8d2362461935698bf95"
 "checksum vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "05c78687fb1a80548ae3250346c3db86a80a7cdd77bda190189f2d0a0987c81a"
 "checksum version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "914b1a6776c4c929a602fafd8bc742e06365d4bcbe48c30f9cca5824f70dc9dd"
+"checksum version_check 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "078775d0255232fb988e6fccf26ddc9d1ac274299aaedcedce21c6f72cc533ce"
 "checksum wait-timeout 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9f200f5b12eb75f8c1ed65abd4b2db8a6e1b138a20de009dacee265a2498f3f6"
 "checksum walkdir 2.2.9 (registry+https://github.com/rust-lang/crates.io-index)" = "9658c94fa8b940eab2250bd5a457f9c48b748420d71293b165c8cdbe2f55f71e"
 "checksum want 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1ce8a968cb1cd110d136ff8b819a556d6fb6d919363c61534f6860c7eb172ba0"
diff --git a/Cargo.toml b/Cargo.toml
index 1280be537b6..b46552f07be 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,6 +25,7 @@ chrono = "0.4"
 clap = "2"
 download = { path = "download" }
 error-chain = "0.12"
+effective-limits = "0.3"
 flate2 = "1"
 git-testament = "0.1.4"
 home = "0.5"
diff --git a/src/dist/component/package.rs b/src/dist/component/package.rs
index d8dfb31a33c..c88e9f02335 100644
--- a/src/dist/component/package.rs
+++ b/src/dist/component/package.rs
@@ -8,6 +8,7 @@ use crate::dist::component::transaction::*;
 use crate::dist::temp;
 use crate::errors::*;
 use crate::utils::notifications::Notification;
+use crate::utils::units;
 use crate::utils::utils;
 
 use std::collections::{HashMap, HashSet};
@@ -17,7 +18,9 @@ use std::io::{self, ErrorKind as IOErrorKind, Read};
 use std::iter::FromIterator;
 use std::mem;
 use std::path::{Path, PathBuf};
+use std::sync::atomic::{AtomicBool, Ordering};
 
+use lazy_static::lazy_static;
 use tar::EntryType;
 
 /// The current metadata revision used by rust-installer
@@ -163,19 +166,40 @@ struct MemoryBudget {
     used: usize,
 }
 
+lazy_static! {
+    static ref RAM_NOTICE_SHOWN: AtomicBool = AtomicBool::new(false);
+}
+
 // Probably this should live in diskio but ¯\_(ツ)_/¯
 impl MemoryBudget {
-    fn new(max_file_size: usize) -> Self {
-        const DEFAULT_UNPACK_RAM: usize = 400 * 1024 * 1024;
-        let unpack_ram = if let Ok(budget_str) = env::var("RUSTUP_UNPACK_RAM") {
-            if let Ok(budget) = budget_str.parse::<usize>() {
-                budget
-            } else {
-                DEFAULT_UNPACK_RAM
+    fn new(max_file_size: usize, effective_max_ram: usize) -> Self {
+        const DEFAULT_UNPACK_RAM_MAX: usize = 500 * 1024 * 1024;
+        const RAM_ALLOWANCE_FOR_RUSTUP_AND_BUFFERS: usize = 100 * 1024 * 1024;
+        let ram_for_unpacking = effective_max_ram - RAM_ALLOWANCE_FOR_RUSTUP_AND_BUFFERS;
+        let default_max_unpack_ram = std::cmp::min(DEFAULT_UNPACK_RAM_MAX, ram_for_unpacking);
+        let unpack_ram = match env::var("RUSTUP_UNPACK_RAM")
+            .ok()
+            .and_then(|budget_str| budget_str.parse::<usize>().ok())
+        {
+            // Note: In future we may want to add a warning or even an override if a user
+            // supplied budget is larger than effective_max_ram.
+            Some(budget) => budget,
+            None => {
+                if RAM_NOTICE_SHOWN.load(Ordering::Acquire) {
+                    eprintln!(
+                        "Defaulting to {} unpack ram",
+                        units::Size::new(
+                            default_max_unpack_ram,
+                            units::Unit::B,
+                            units::UnitMode::Norm
+                        )
+                    );
+                    RAM_NOTICE_SHOWN.store(true, Ordering::Release);
+                }
+                default_max_unpack_ram
             }
-        } else {
-            DEFAULT_UNPACK_RAM
         };
+
         if max_file_size > unpack_ram {
             panic!("RUSTUP_UNPACK_RAM must be larger than {}", max_file_size);
         }
@@ -278,7 +302,8 @@ fn unpack_without_first_dir<'a, R: Read>(
         .entries()
         .chain_err(|| ErrorKind::ExtractingPackage)?;
     const MAX_FILE_SIZE: u64 = 200_000_000;
-    let mut budget = MemoryBudget::new(MAX_FILE_SIZE as usize);
+    let effective_max_ram = effective_limits::memory_limit()?;
+    let mut budget = MemoryBudget::new(MAX_FILE_SIZE as usize, effective_max_ram as usize);
 
     let mut directories: HashMap<PathBuf, DirStatus> = HashMap::new();
     // Path is presumed to exist. Call it a precondition.
diff --git a/src/errors.rs b/src/errors.rs
index d0d5c534a15..13c4dc4c816 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -22,6 +22,7 @@ pub const TOOLSTATE_MSG: &str =
 error_chain! {
     links {
         Download(download::Error, download::ErrorKind);
+        Limits(effective_limits::Error, effective_limits::ErrorKind);
     }
 
     foreign_links {
diff --git a/tests/cli-exact.rs b/tests/cli-exact.rs
index dfbddf30813..b0dc52d9055 100644
--- a/tests/cli-exact.rs
+++ b/tests/cli-exact.rs
@@ -38,6 +38,7 @@ info: downloading component 'rust-docs'
 info: downloading component 'rust-std'
 info: downloading component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
@@ -172,6 +173,7 @@ info: downloading component 'rust-docs'
 info: downloading component 'rust-std'
 info: downloading component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
@@ -504,6 +506,7 @@ fn cross_install_indicates_target() {
             &format!(
                 r"info: downloading component 'rust-std' for '{0}'
 info: installing component 'rust-std' for '{0}'
+Defaulting to 500.0 MiB unpack ram
 ",
                 clitools::CROSS_ARCH1
             ),
diff --git a/tests/cli-rustup.rs b/tests/cli-rustup.rs
index 77d70f90fa4..17ca87fe657 100644
--- a/tests/cli-rustup.rs
+++ b/tests/cli-rustup.rs
@@ -56,6 +56,7 @@ info: removing previous version of component 'rust-docs'
 info: removing previous version of component 'rust-std'
 info: removing previous version of component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
@@ -96,6 +97,7 @@ info: removing previous version of component 'rust-docs'
 info: removing previous version of component 'rust-std'
 info: removing previous version of component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
@@ -160,6 +162,7 @@ info: removing previous version of component 'rust-docs'
 info: removing previous version of component 'rust-std'
 info: removing previous version of component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
@@ -230,6 +233,7 @@ info: removing previous version of component 'rust-docs'
 info: removing previous version of component 'rust-std'
 info: removing previous version of component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
@@ -291,6 +295,7 @@ info: downloading component 'rust-docs'
 info: downloading component 'rust-std'
 info: downloading component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
diff --git a/tests/cli-self-upd.rs b/tests/cli-self-upd.rs
index d27dac8b0b8..f0f7ff135b7 100644
--- a/tests/cli-self-upd.rs
+++ b/tests/cli-self-upd.rs
@@ -883,6 +883,7 @@ info: downloading component 'rust-docs'
 info: downloading component 'rust-std'
 info: downloading component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rust-std'
 info: installing component 'rustc'
diff --git a/tests/cli-v2.rs b/tests/cli-v2.rs
index a7ad3a9a389..78b2786c89e 100644
--- a/tests/cli-v2.rs
+++ b/tests/cli-v2.rs
@@ -1342,6 +1342,7 @@ info: downloading component 'cargo'
 info: downloading component 'rust-docs'
 info: downloading component 'rustc'
 info: installing component 'cargo'
+Defaulting to 500.0 MiB unpack ram
 info: installing component 'rust-docs'
 info: installing component 'rustc'
 "