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[PULL 17/28] block: add max_hw_transfer to BlockLimits
From: |
Paolo Bonzini |
Subject: |
[PULL 17/28] block: add max_hw_transfer to BlockLimits |
Date: |
Fri, 25 Jun 2021 16:18:11 +0200 |
For block host devices, I/O can happen through either the kernel file
descriptor I/O system calls (preadv/pwritev, io_submit, io_uring)
or the SCSI passthrough ioctl SG_IO.
In the latter case, the size of each transfer can be limited by the
HBA, while for file descriptor I/O the kernel is able to split and
merge I/O in smaller pieces as needed. Applying the HBA limits to
file descriptor I/O results in more system calls and suboptimal
performance, so this patch splits the max_transfer limit in two:
max_transfer remains valid and is used in general, while max_hw_transfer
is limited to the maximum hardware size. max_hw_transfer can then be
included by the scsi-generic driver in the block limits page, to ensure
that the stricter hardware limit is used.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
block/block-backend.c | 13 +++++++++++++
block/file-posix.c | 2 +-
block/io.c | 2 ++
hw/scsi/scsi-generic.c | 2 +-
include/block/block_int.h | 7 +++++++
include/sysemu/block-backend.h | 1 +
6 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index 6e37582740..deb55c272e 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1953,6 +1953,19 @@ uint32_t blk_get_request_alignment(BlockBackend *blk)
return bs ? bs->bl.request_alignment : BDRV_SECTOR_SIZE;
}
+/* Returns the maximum hardware transfer length, in bytes; guaranteed nonzero
*/
+uint64_t blk_get_max_hw_transfer(BlockBackend *blk)
+{
+ BlockDriverState *bs = blk_bs(blk);
+ uint64_t max = INT_MAX;
+
+ if (bs) {
+ max = MIN_NON_ZERO(max, bs->bl.max_hw_transfer);
+ max = MIN_NON_ZERO(max, bs->bl.max_transfer);
+ }
+ return ROUND_DOWN(max, blk_get_request_alignment(blk));
+}
+
/* Returns the maximum transfer length, in bytes; guaranteed nonzero */
uint32_t blk_get_max_transfer(BlockBackend *blk)
{
diff --git a/block/file-posix.c b/block/file-posix.c
index 6db690baf2..88e58d2863 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1232,7 +1232,7 @@ static void raw_refresh_limits(BlockDriverState *bs,
Error **errp)
int ret = sg_get_max_transfer_length(s->fd);
if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
- bs->bl.max_transfer = pow2floor(ret);
+ bs->bl.max_hw_transfer = pow2floor(ret);
}
ret = sg_get_max_segments(s->fd);
diff --git a/block/io.c b/block/io.c
index 323854d063..dd93364258 100644
--- a/block/io.c
+++ b/block/io.c
@@ -127,6 +127,8 @@ static void bdrv_merge_limits(BlockLimits *dst, const
BlockLimits *src)
{
dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
+ dst->max_hw_transfer = MIN_NON_ZERO(dst->max_hw_transfer,
+ src->max_hw_transfer);
dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
src->opt_mem_alignment);
dst->min_mem_alignment = MAX(dst->min_mem_alignment,
diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index b6c4143dc7..665baf900e 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -179,7 +179,7 @@ static int scsi_handle_inquiry_reply(SCSIGenericReq *r,
SCSIDevice *s, int len)
(r->req.cmd.buf[1] & 0x01)) {
page = r->req.cmd.buf[2];
if (page == 0xb0) {
- uint32_t max_transfer = blk_get_max_transfer(s->conf.blk);
+ uint64_t max_transfer = blk_get_max_hw_transfer(s->conf.blk);
uint32_t max_iov = blk_get_max_iov(s->conf.blk);
assert(max_transfer);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 057d88b1fc..f1a54db0f8 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -695,6 +695,13 @@ typedef struct BlockLimits {
* clamped down. */
uint32_t max_transfer;
+ /* Maximal hardware transfer length in bytes. Applies whenever
+ * transfers to the device bypass the kernel I/O scheduler, for
+ * example with SG_IO. If larger than max_transfer or if zero,
+ * blk_get_max_hw_transfer will fall back to max_transfer.
+ */
+ uint64_t max_hw_transfer;
+
/* memory alignment, in bytes so that no bounce buffer is needed */
size_t min_mem_alignment;
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 5423e3d9c6..9ac5f7bbd3 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -208,6 +208,7 @@ void blk_eject(BlockBackend *blk, bool eject_flag);
int blk_get_flags(BlockBackend *blk);
uint32_t blk_get_request_alignment(BlockBackend *blk);
uint32_t blk_get_max_transfer(BlockBackend *blk);
+uint64_t blk_get_max_hw_transfer(BlockBackend *blk);
int blk_get_max_iov(BlockBackend *blk);
void blk_set_guest_block_size(BlockBackend *blk, int align);
void *blk_try_blockalign(BlockBackend *blk, size_t size);
--
2.31.1
- [PULL 08/28] configure, meson: convert pam detection to meson, (continued)
- [PULL 08/28] configure, meson: convert pam detection to meson, Paolo Bonzini, 2021/06/25
- [PULL 10/28] configure, meson: convert libcacard detection to meson, Paolo Bonzini, 2021/06/25
- [PULL 11/28] configure, meson: convert libusbredir detection to meson, Paolo Bonzini, 2021/06/25
- [PULL 07/28] configure, meson: convert libtasn1 detection to meson, Paolo Bonzini, 2021/06/25
- [PULL 12/28] KVM: Fix dirty ring mmap incorrect size due to renaming accident, Paolo Bonzini, 2021/06/25
- [PULL 13/28] file-posix: fix max_iov for /dev/sg devices, Paolo Bonzini, 2021/06/25
- [PULL 14/28] scsi-generic: pass max_segments via max_iov field in BlockLimits, Paolo Bonzini, 2021/06/25
- [PULL 16/28] block-backend: align max_transfer to request alignment, Paolo Bonzini, 2021/06/25
- [PULL 15/28] osdep: provide ROUND_DOWN macro, Paolo Bonzini, 2021/06/25
- [PULL 17/28] block: add max_hw_transfer to BlockLimits,
Paolo Bonzini <=
- [PULL 18/28] file-posix: try BLKSECTGET on block devices too, do not round to power of 2, Paolo Bonzini, 2021/06/25
- [PULL 19/28] block: feature detection for host block support, Paolo Bonzini, 2021/06/25
- [PULL 21/28] block: try BSD disk size ioctls one after another, Paolo Bonzini, 2021/06/25
- [PULL 20/28] block: check for sys/disk.h, Paolo Bonzini, 2021/06/25
- [PULL 22/28] block: detect DKIOCGETBLOCKCOUNT/SIZE before use, Paolo Bonzini, 2021/06/25
- [PULL 23/28] file-posix: handle EINTR during ioctl, Paolo Bonzini, 2021/06/25
- [PULL 25/28] machine: move common smp_parse code to caller, Paolo Bonzini, 2021/06/25
- [PULL 26/28] machine: add error propagation to mc->smp_parse, Paolo Bonzini, 2021/06/25
- [PULL 24/28] machine: move dies from X86MachineState to CpuTopology, Paolo Bonzini, 2021/06/25
- [PULL 27/28] machine: pass QAPI struct to mc->smp_parse, Paolo Bonzini, 2021/06/25