Implement initializer() for FileDesc #53981
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
in order to avoid constantly zeroing memory when it's not needed.
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r? @sfackler from the git history I think this could be interesting to you. |
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@bors r+ Thanks! |
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📌 Commit 28745a6 has been approved by |
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kennytm
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Sep 8, 2018
Implement initializer() for FileDesc
Here was my initial issue:
```rust
use std::process::{Command};
fn main() {
let output = Command::new("curl").arg("-s").arg("http://ovh.net/files/100Mio.dat").output();
println!("{:?}", output.unwrap().stdout.len());
}
```
```
~/stuff ❯❯❯ time ./dwl
104857600
./dwl 16.22s user 1.80s system 23% cpu 1:15.24 total
```
```rust
use std::process::{Command, Stdio};
fn main() {
let child = Command::new("curl").arg("-s").arg("http://ovh.net/files/100Mio.dat").stdout(Stdio::piped()).spawn();
let output = child.unwrap().wait_with_output().unwrap();
println!("{:?}", output.stdout.len());
}
```
```
~/stuff ❯❯❯ time ./dwl2
104857600
./dwl2 0.64s user 2.18s system 5% cpu 53.072 total
```
As you can see the first version is spending much more time in userland and also uses more cpu. With the help of @programble, @talchas and @habnabit on the rust IRC, we discovered that the slow version uses two pipes, one for `stdin` and one for `stderr` and in that case it polls when going through [this function](https://github.com/rust-lang/rust/blob/master/src/libstd/sys/unix/pipe.rs#L82). The polling calls `read_to_end` on the pipes repetitively and this results in zeroing its internal buffer each time. To avoid this zeroing, `FileDesc` needs to implement `initializer`. We see no reason why it [wouldn't work with uninitialized memory](https://doc.rust-lang.org/1.26.1/src/std/io/mod.rs.html#534) so this PR fixes that.
Here is some tracing of the slow program:
versus the fast program:
I have not tested the change yet but will try to build it tomorrow.
bors
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that referenced
this pull request
Sep 8, 2018
Rollup of 11 pull requests Successful merges: - #51366 (stabilize #[panic_handler]) - #53162 (rustdoc: collect trait impls as an early pass) - #53932 ([NLL] Remove base_place) - #53942 (Rewrite `precompute_borrows_out_of_scope` for fewer hash table lookups.) - #53973 (Have rust-lldb look for the rust-enabled lldb) - #53981 (Implement initializer() for FileDesc) - #53987 (rustbuild: allow configuring llvm version suffix) - #53993 (rustc_resolve: don't record uniform_paths canaries as reexports.) - #54007 (crates that provide a `panic_handler` are exempt from the `unused_extern_crates` lint) - #54040 (update books for next release) - #54050 (Update `petgraph` dependency to 0.4.13 to fix build with nightly) Failed merges: r? @ghost
kennytm
added a commit
to kennytm/rust
that referenced
this pull request
Sep 8, 2018
Implement initializer() for FileDesc
Here was my initial issue:
```rust
use std::process::{Command};
fn main() {
let output = Command::new("curl").arg("-s").arg("http://ovh.net/files/100Mio.dat").output();
println!("{:?}", output.unwrap().stdout.len());
}
```
```
~/stuff ❯❯❯ time ./dwl
104857600
./dwl 16.22s user 1.80s system 23% cpu 1:15.24 total
```
```rust
use std::process::{Command, Stdio};
fn main() {
let child = Command::new("curl").arg("-s").arg("http://ovh.net/files/100Mio.dat").stdout(Stdio::piped()).spawn();
let output = child.unwrap().wait_with_output().unwrap();
println!("{:?}", output.stdout.len());
}
```
```
~/stuff ❯❯❯ time ./dwl2
104857600
./dwl2 0.64s user 2.18s system 5% cpu 53.072 total
```
As you can see the first version is spending much more time in userland and also uses more cpu. With the help of @programble, @talchas and @habnabit on the rust IRC, we discovered that the slow version uses two pipes, one for `stdin` and one for `stderr` and in that case it polls when going through [this function](https://github.com/rust-lang/rust/blob/master/src/libstd/sys/unix/pipe.rs#L82). The polling calls `read_to_end` on the pipes repetitively and this results in zeroing its internal buffer each time. To avoid this zeroing, `FileDesc` needs to implement `initializer`. We see no reason why it [wouldn't work with uninitialized memory](https://doc.rust-lang.org/1.26.1/src/std/io/mod.rs.html#534) so this PR fixes that.
Here is some tracing of the slow program:
versus the fast program:
I have not tested the change yet but will try to build it tomorrow.
bors
added a commit
that referenced
this pull request
Sep 8, 2018
Rollup of 10 pull requests Successful merges: - #53315 (use `NonZeroU32` in `newtype_index!`macro, change syntax) - #53932 ([NLL] Remove base_place) - #53942 (Rewrite `precompute_borrows_out_of_scope` for fewer hash table lookups.) - #53973 (Have rust-lldb look for the rust-enabled lldb) - #53981 (Implement initializer() for FileDesc) - #53987 (rustbuild: allow configuring llvm version suffix) - #53993 (rustc_resolve: don't record uniform_paths canaries as reexports.) - #54007 (crates that provide a `panic_handler` are exempt from the `unused_extern_crates` lint) - #54040 (update books for next release) - #54050 (Update `petgraph` dependency to 0.4.13 to fix build with nightly)
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Here was my initial issue:
As you can see the first version is spending much more time in userland and also uses more cpu. I discovered that the slow version uses two pipes, one for
stdinand one forstderrand in that case it polls when going through this function. The polling callsread_to_endon the pipes repetitively and this results in zeroing its internal buffer each time. To avoid this zeroing,FileDescneeds to implementinitializer. I see no reason why it wouldn't work with uninitialized memory so this PR fixes that.Here is some tracing of the slow program:
versus the fast program:
I have not tested the change yet but will try to build it tomorrow.