Nowaday SCSI drivers in guests are able to align UNMAP requests before
sending to the device. Right now QEMU provides an ability to set
this via "discard_granularity" property of the block device which could
be used by management layer.
Though, in particular, from the point of QEMU, there is
pdiscard_granularity on the format driver level, f.e. on QCOW2 or iSCSI.
It would be beneficial to pass this value as a default for this
property.
Technically this should reduce the amount of use less UNMAP requests
from the guest to the host. Basic test confirms this.
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Kevin Wolf <kw...@redhat.com>
CC: Max Reitz <mre...@redhat.com>
CC: Eduardo Habkost <ehabk...@redhat.com>
CC: Marcel Apfelbaum <marcel.apfelb...@gmail.com>
CC: John Snow <js...@redhat.com>
CC: Paolo Bonzini <pbonz...@redhat.com>
CC: Fam Zheng <f...@euphon.net>
---
block/block-backend.c | 11 +++++++++++
hw/core/machine.c | 15 ++++++++++++++-
hw/ide/qdev.c | 3 ++-
hw/scsi/scsi-disk.c | 5 ++++-
include/hw/block/block.h | 2 +-
include/sysemu/block-backend.h | 6 ++++++
6 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index 6936b25c83..9342a475cb 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2222,6 +2222,17 @@ int blk_probe_geometry(BlockBackend *blk, HDGeometry
*geo)
return bdrv_probe_geometry(blk_bs(blk), geo);
}
+int blk_discard_granularity(BlockBackend *blk)
+{
+ BlockDriverState *bs = blk_bs(blk);
+
+ if (bs == NULL) {
+ return DEFAULT_DISCARD_GRANULARITY;
+ }
+
+ return bs->bl.pdiscard_alignment;
+}
+
/*
* Updates the BlockBackendRootState object with data from the currently
* attached BlockDriverState.
diff --git a/hw/core/machine.c b/hw/core/machine.c
index bb3a7b18b1..08a242d606 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -28,7 +28,20 @@
#include "hw/mem/nvdimm.h"
#include "migration/vmstate.h"
-GlobalProperty hw_compat_5_0[] = {};
+GlobalProperty hw_compat_5_0[] = {
+ { "ide-cd", "discard_granularity", "0xffffffff" },
+ { "ide-hd", "discard_granularity", "0xffffffff" },
+ { "ide-drive", "discard_granularity", "0xffffffff" },
+ { "scsi-hd", "discard_granularity", "0xffffffff" },
+ { "scsi-cd", "discard_granularity", "0xffffffff" },
+ { "scsi-disk", "discard_granularity", "0xffffffff" },
+ { "virtio-blk-pci", "discard_granularity", "0xffffffff" },
+ { "xen-block", "discard_granularity", "0xffffffff" },
+ { "usb-storage", "discard_granularity", "0xffffffff" },
+ { "swim-drive", "discard_granularity", "0xffffffff" },
+ { "floppy", "discard_granularity", "0xffffffff" },
+ { "nvme", "discard_granularity", "0xffffffff" },
+};
const size_t hw_compat_5_0_len = G_N_ELEMENTS(hw_compat_5_0);
GlobalProperty hw_compat_4_2[] = {
diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
index 06b11583f5..e515dbeb0e 100644
--- a/hw/ide/qdev.c
+++ b/hw/ide/qdev.c
@@ -179,7 +179,8 @@ static void ide_dev_initfn(IDEDevice *dev, IDEDriveKind
kind, Error **errp)
}
}
- if (dev->conf.discard_granularity == -1) {
+ if (dev->conf.discard_granularity == -1 ||
+ dev->conf.discard_granularity == -2) {
dev->conf.discard_granularity = 512;
} else if (dev->conf.discard_granularity &&
dev->conf.discard_granularity != 512) {
diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 387503e11b..6b809608e4 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -48,7 +48,6 @@
#define SCSI_MAX_INQUIRY_LEN 256
#define SCSI_MAX_MODE_LEN 256
-#define DEFAULT_DISCARD_GRANULARITY (4 * KiB)
#define DEFAULT_MAX_UNMAP_SIZE (1 * GiB)
#define DEFAULT_MAX_IO_SIZE INT_MAX /* 2 GB - 1 block */
@@ -2381,6 +2380,10 @@ static void scsi_realize(SCSIDevice *dev, Error **errp)
if (s->qdev.conf.discard_granularity == -1) {
s->qdev.conf.discard_granularity =
MAX(s->qdev.conf.logical_block_size, DEFAULT_DISCARD_GRANULARITY);
+ } else if (s->qdev.conf.discard_granularity == -2) {
+ s->qdev.conf.discard_granularity =
+ MAX(s->qdev.conf.logical_block_size,
+ blk_discard_granularity(s->qdev.conf.blk));
}
if (!s->version) {
diff --git a/include/hw/block/block.h b/include/hw/block/block.h
index d7246f3862..53d4a38044 100644
--- a/include/hw/block/block.h
+++ b/include/hw/block/block.h
@@ -54,7 +54,7 @@ static inline unsigned int get_physical_block_exp(BlockConf
*conf)
DEFINE_PROP_UINT16("min_io_size", _state, _conf.min_io_size, 0), \
DEFINE_PROP_UINT32("opt_io_size", _state, _conf.opt_io_size, 0), \
DEFINE_PROP_UINT32("discard_granularity", _state, \
- _conf.discard_granularity, -1), \
+ _conf.discard_granularity, -2), \
DEFINE_PROP_ON_OFF_AUTO("write-cache", _state, _conf.wce, \
ON_OFF_AUTO_AUTO), \
DEFINE_PROP_BOOL("share-rw", _state, _conf.share_rw, false)
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 8203d7f6f9..241a759432 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -13,6 +13,7 @@
#ifndef BLOCK_BACKEND_H
#define BLOCK_BACKEND_H
+#include "qemu/units.h"
#include "qemu/iov.h"
#include "block/throttle-groups.h"
@@ -25,6 +26,10 @@
*/
#include "block/block.h"
+
+#define DEFAULT_DISCARD_GRANULARITY (4 * KiB)
+
+
/* Callbacks for block device models */
typedef struct BlockDevOps {
/*
@@ -246,6 +251,7 @@ int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size);
int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz);
int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo);
+int blk_discard_granularity(BlockBackend *blk);
BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
BlockCompletionFunc *cb,
void *opaque, int ret);
--
2.17.1
