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devmapper: Add blkdiscard option and disable it on raw devices

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The blkdiscard hack we do on container/image delete is pretty slow, but
required to restore space to the "host" root filesystem. However, it
is pretty useless on raw devices, and you may not need it in development
either.

In a simple test of the devicemapper backend on loopback the time to
delete 20 container went from 11 seconds to 0.4 seconds with
--storage-opt blkdiscard=false.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This commit is contained in:
Alexander Larsson 2014-04-01 15:41:25 +02:00
parent a226168a8b
commit 0434a2ce64
2 changed files with 38 additions and 6 deletions
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16
daemon/graphdriver/devmapper/README.md
View file

@ -125,3 +125,19 @@ Here is the list of supported options:
Example use:
``docker -d --storage-opt dm.datadev=/dev/sdb1 --storage-opt dm.metadatadev=/dev/sdc1``
* `dm.blkdiscard`
Enables or disables the use of blkdiscard when removing
devicemapper devices. This is enabled by default (only) if using
loopback devices and is required to res-parsify the loopback file
on image/container removal.
Disabling this on loopback can lead to *much* faster container
removal times, but will make the space used in /var/lib/docker
directory not be returned to the system for other use when
containers are removed.
Example use:
``docker -d --storage-opt dm.blkdiscard=false``

28
daemon/graphdriver/devmapper/deviceset.go
View file

@ -77,6 +77,7 @@ type DeviceSet struct {
mkfsArgs []string
dataDevice string
metadataDevice string
doBlkDiscard bool
}
type DiskUsage struct {
@ -713,12 +714,14 @@ func (devices *DeviceSet) AddDevice(hash, baseHash string) error {
}
func (devices *DeviceSet) deleteDevice(info *DevInfo) error {
// This is a workaround for the kernel not discarding block so
// on the thin pool when we remove a thinp device, so we do it
// manually
if err := devices.activateDeviceIfNeeded(info); err == nil {
if err := BlockDeviceDiscard(info.DevName()); err != nil {
utils.Debugf("Error discarding block on device: %s (ignoring)\n", err)
if devices.doBlkDiscard {
// This is a workaround for the kernel not discarding block so
// on the thin pool when we remove a thinp device, so we do it
// manually
if err := devices.activateDeviceIfNeeded(info); err == nil {
if err := BlockDeviceDiscard(info.DevName()); err != nil {
utils.Debugf("Error discarding block on device: %s (ignoring)\n", err)
}
}
}
@ -1174,8 +1177,10 @@ func NewDeviceSet(root string, doInit bool, options []string) (*DeviceSet, error
metaDataLoopbackSize: DefaultMetaDataLoopbackSize,
baseFsSize: DefaultBaseFsSize,
filesystem: "ext4",
doBlkDiscard: true,
}
foundBlkDiscard := false
for _, option := range options {
key, val, err := utils.ParseKeyValueOpt(option)
if err != nil {
@ -1214,11 +1219,22 @@ func NewDeviceSet(root string, doInit bool, options []string) (*DeviceSet, error
devices.metadataDevice = val
case "dm.datadev":
devices.dataDevice = val
case "dm.blkdiscard":
foundBlkDiscard = true
devices.doBlkDiscard, err = strconv.ParseBool(val)
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("Unknown option %s\n", key)
}
}
// By default, don't do blk discard hack on raw devices, its rarely useful and is expensive
if !foundBlkDiscard && devices.dataDevice != "" {
devices.doBlkDiscard = false
}
if err := devices.initDevmapper(doInit); err != nil {
return nil, err
}