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Vivek Goyal c86243b090 ovl: provide a mount option "volatile"
Container folks are complaining that dnf/yum issues too many sync while
installing packages and this slows down the image build. Build requirement
is such that they don't care if a node goes down while build was still
going on. In that case, they will simply throw away unfinished layer and
start new build. So they don't care about syncing intermediate state to the
disk and hence don't want to pay the price associated with sync.

So they are asking for mount options where they can disable sync on overlay
mount point.

They primarily seem to have two use cases.

- For building images, they will mount overlay with nosync and then sync
  upper layer after unmounting overlay and reuse upper as lower for next
  layer.

- For running containers, they don't seem to care about syncing upper layer
  because if node goes down, they will simply throw away upper layer and
  create a fresh one.

So this patch provides a mount option "volatile" which disables all forms
of sync. Now it is caller's responsibility to throw away upper if system
crashes or shuts down and start fresh.

With "volatile", I am seeing roughly 20% speed up in my VM where I am just
installing emacs in an image. Installation time drops from 31 seconds to 25
seconds when nosync option is used. This is for the case of building on top
of an image where all packages are already cached. That way I take out the
network operations latency out of the measurement.

Giuseppe is also looking to cut down on number of iops done on the disk. He
is complaining that often in cloud their VMs are throttled if they cross
the limit. This option can help them where they reduce number of iops (by
cutting down on frequent sync and writebacks).

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
arch Three interrupt related fixes for X86: 2020-08-30 12:01:23 -07:00
block io_uring-5.9-2020-08-23 2020-08-24 11:53:15 -07:00
certs
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-30 15:53:44 -07:00
Documentation ovl: provide a mount option "volatile" 2020-09-02 10:58:48 +02:00
drivers Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-30 15:53:44 -07:00
fs ovl: provide a mount option "volatile" 2020-09-02 10:58:48 +02:00
include A set of fixes for interrupt chip drivers: 2020-08-30 11:56:54 -07:00
init OpenRISC updates for 5.9 2020-08-14 14:04:53 -07:00
ipc treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
kernel Three interrupt related fixes for X86: 2020-08-30 12:01:23 -07:00
lib lib: Revert use of fallthrough pseudo-keyword in lib/ 2020-08-24 14:17:44 -07:00
LICENSES
mm powerpc fixes for 5.9 #4 2020-08-30 10:56:12 -07:00
net Fixes: 2020-08-25 18:01:36 -07:00
samples treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
scripts kconfig: qconf: replace deprecated QString::sprintf() with QTextStream 2020-08-21 10:23:38 +09:00
security treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
sound treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
tools powerpc fixes for 5.9 #4 2020-08-30 10:56:12 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt * PAE and PKU bugfixes for x86 2020-08-22 10:03:05 -07:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap Merge branch 'akpm' (patches from Andrew) 2020-08-21 14:44:48 -07:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Three interrupt related fixes for X86: 2020-08-30 12:01:23 -07:00
Makefile Linux 5.9-rc3 2020-08-30 16:01:54 -07:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.