syncthing/lib/osutil/rlimit_unix.go

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// Copyright (C) 2015 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
// +build !windows
package osutil
import "syscall"
// MaximizeOpenFileLimit tries to set the resource limit RLIMIT_NOFILE (number
// of open file descriptors) to the max (hard limit), if the current (soft
// limit) is below the max. Returns the new (though possibly unchanged) limit,
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// or an error if it could not be changed.
func MaximizeOpenFileLimit() (int, error) {
// Get the current limit on number of open files.
var lim syscall.Rlimit
if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim); err != nil {
return 0, err
}
// If we're already at max, there's no need to try to raise the limit.
if lim.Cur >= lim.Max {
return int(lim.Cur), nil
}
// Try to increase the limit to the max.
oldLimit := lim.Cur
lim.Cur = lim.Max
if err := syscall.Setrlimit(syscall.RLIMIT_NOFILE, &lim); err != nil {
return int(oldLimit), err
}
// If the set succeeded, perform a new get to see what happened. We might
// have gotten a value lower than the one in lim.Max, if lim.Max was
// something that indicated "unlimited" (i.e. intmax).
if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim); err != nil {
// We don't really know the correct value here since Getrlimit
// mysteriously failed after working once... Shouldn't ever happen, I
// think.
return 0, err
}
return int(lim.Cur), nil
}