The case of the stalled CPU controller [LWN.net]
Long-running technical disagreements are certainly well-known in the kernel community. Usually they are eventually resolved and the developers involved move on to new problems. Occasionally, though, stalled consensus can lead to a break between the kernel and its user community. The ongoing dispute over the CPU controller in the new control-group hierarchy is beginning to look like one of those un
Macvlan vs Ipvlan
I’ve covered macvlans in the Bridge vs Macvlan post. If you are new to macvlan concept, go ahead and read it first. Macvlan To recap: Macvlan allows you to configure sub-interfaces (also termed slave devices) of a parent, physical Ethernet interface (also termed upper device), each with its own unique MAC address, and consequently its own IP address. Applications, VMs and containers can then bind
sched/cpuacct: Split usage accounting into user_usage and sys_usage
sched/cpuacct: Split usage accounting into user_usage and sys_usage Sometimes, cpuacct.usage is not detailed enough to see how much CPU usage a group had. We want to know how much time it used in user mode and how much in kernel mode. This patch introduces more files to give this information: # ls /sys/fs/cgroup/cpuacct/cpuacct.usage* /sys/fs/cgroup/cpuacct/cpuacct.usage /sys/fs/cgroup/cpuacct/cpu
CPU使用率100％のWebサーバをOSのチューニングだけでCPU使用率20%まで改善する - 人間とウェブの未来
こんばんは、 @matsumotoryです。 hb.matsumoto-r.jp 上記エントリにおいて、プロセスの大量メモリ確保に伴うページテーブルサイズとベージテーブルエントリ数の肥大化によるcloneやexecveの性能劣化とCPU使用時間の専有問題、および、それらの解決方法についてシステムコールレベルで確認しました。 そこで今回は、システムコールやそのカーネル内部の処理の性能、というよりは、より実践的な環境であるApache httpdとmod_cgiを用いて、phpinfo()を実行するだけのCGIに対してベンチマークをかけた時にどれぐらいCPUのidleが空くか、システムCPUの使用量が変わるかを、前回示した解決方法の1つであるHugePagesを使うかどうかの観点で比較してみましょう。 特定条件下のWebサーバ環境のシステムCPUに起因する高負荷問題から、システムコールやカーネ
x86: Intel Cache Allocation Technology support [LWN.net]
<1416445539-24856-1-git-send-email-vikas.shivappa@linux.intel.com> vikas.shivappa@intel.com, vikas.shivappa@linux.intel.com, hpa@zytor.com, tglx@linutronix.de, mingo@kernel.org, tj@kernel.org, matt.flemming@intel.com, will.auld@intel.com, peterz@infradead.org What is Cache Allocation Technology ( CAT ) ------------------------------------------- Cache Allocation Technology provides a way for the S
Mount namespaces, mount propagation, and unbindable mounts [LWN.net]
Mount namespaces, mount propagation, and unbindable mounts In the previous installment of our article series on namespaces, we looked at the key concepts underlying mount namespaces and shared subtrees, including the notions of mount propagation types and peer groups. In this article, we provide some practical demonstrations of the operation of the various propagation types: MS_SHARED, MS_PRIVATE,
Mount namespaces and shared subtrees [LWN.net]
Did you know...?LWN.net is a subscriber-supported publication; we rely on subscribers to keep the entire operation going. Please help out by buying a subscription and keeping LWN on the net. Mount namespaces are a powerful and flexible tool for creating per-user and per-container filesystem trees. They are also a surprisingly complex feature; in this continuation of our series on namespaces we unr
General unprivileged mount support [LWN.net]
Linux Containers <containers@lists.linux-foundation.org>, <linux-fsdevel@vger.kernel.org>, Linux API <linux-api@vger.kernel.org>, James Bottomley <James.Bottomley@HansenPartnership.com>, Djalal Harouni <tixxdz@gmail.com>, "Serge E. Hallyn" <serge@hallyn.com>, Andy Lutomirski <luto@amacapital.net>, Jan Kara <jack@suse.cz>, Jann Horn <jannh@google.com>, Michael Kerrisk <mtk.manpages@gmail.com> As we
namespaces: add transparent user namespaces [LWN.net]
This allows the admin of a user namespace to mark the namespace as transparent. All other namespaces, by default, are opaque. While the current behavior of user namespaces is appropriate for use in containers, there are many programs that only use user namespaces because doing so enables them to do other things (e.g. unsharing the mount or network namespace) that require namespaced capabilities. F
Present useful limits to user [LWN.net]
Hello, There are many basic ways to control processes, including capabilities, cgroups and resource limits. However, there are far fewer ways to find out useful values for the limits, except blind trial and error. This patch series attempts to fix that by giving at least a nice starting point from the actual maximum values. I looked where each limit is checked and added a call to limit bump nearby
Linuxカーネルのコードを読んで勉強になったこと - φ(・・*)ゞ ｳｰﾝ カーネルとか弄ったりのメモ
Linuxカーネルのコードを読んでて、なるほど〜と思うことはよくあるけど、その中でも特に今までの考え方をぶち壊してくれたのはなんだっけと思ったところ、やっぱりリスト構造かなと言うところ。 c言語でリスト構造を作る場合、一般的な教科書方式だと↓のようにデータとnextポインタは密結合になってると思います。これの場合、struct foobarのポインタをnext要素に使っているので、他の構造体（例えば、struct hogehoge）で同じことをしようとすると、その構造体ではstruct hogehoge *nextというメンバ変数を持つ必要があります。 ヘッド要素はstruct foobarです。 struct foobar { int n; char s[64]; struct foobar *next; }; struct foobar head; Linuxカーネルの場合、データとリ
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[Documentation] State of CPU controller in cgroup v2 [LWN.net]
Filesystem mounts in user namespaces — one year later [LWN.net]
IPvlan Eric Dumazet (edumazet@google.com) Mahesh Bandewar (maheshb@google.com) IPvlan (instead of MACvlan) : Why? ● Switches may apply policies to disable CAM-table overflow essentially allowing a mac-address per incoming frame per port ● Excessive u
https://people.netfilter.org/pablo/netdev0.1/papers/IPVLAN-The-beginning.pdf
userns: sysctl limits for namespaces [LWN.net]
userns: sysctl limits for namespaces [LWN.net]
cgroup: allow for unprivileged management [LWN.net]
Inotify limits per usernamespace [LWN.net]
perf: Container-aware tracing support [LWN.net]