From: Paolo Bonzini <pbonzini@redhat.com>
To: qemu-devel@nongnu.org
Cc: kwolf@redhat.com, qemu-block@nongnu.org
Subject: [PATCH v3 3/7] block: add max_hw_transfer to BlockLimits
Date: Thu, 3 Jun 2021 15:37:18 +0200 [thread overview]
Message-ID: <20210603133722.218465-4-pbonzini@redhat.com> (raw)
In-Reply-To: <20210603133722.218465-1-pbonzini@redhat.com>
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 | 12 ++++++++++++
block/file-posix.c | 2 +-
block/io.c | 1 +
hw/scsi/scsi-generic.c | 2 +-
include/block/block_int.h | 7 +++++++
include/sysemu/block-backend.h | 1 +
6 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index 15f1ea4288..2ea1412a54 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1953,6 +1953,18 @@ 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(bs->bl.max_hw_transfer, bs->bl.max_transfer);
+ }
+ return max;
+}
+
/* 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 e3241a0dd3..f55f92d0f5 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1234,7 +1234,7 @@ 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..089b99bb0c 100644
--- a/block/io.c
+++ b/block/io.c
@@ -127,6 +127,7 @@ 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 82e1e2ee79..3762dce749 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -179,7 +179,7 @@ static void scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s)
(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
next prev parent reply other threads:[~2021-06-03 13:40 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-03 13:37 [PATCH v3 0/7] block: file-posix queue Paolo Bonzini
2021-06-03 13:37 ` [PATCH v3 1/7] file-posix: fix max_iov for /dev/sg devices Paolo Bonzini
2021-06-07 5:39 ` Vladimir Sementsov-Ogievskiy
2021-06-07 6:16 ` Vladimir Sementsov-Ogievskiy
2021-06-07 7:23 ` Vladimir Sementsov-Ogievskiy
2021-06-15 15:58 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 2/7] scsi-generic: pass max_segments via max_iov field in BlockLimits Paolo Bonzini
2021-06-15 16:06 ` Max Reitz
2021-06-15 16:20 ` Max Reitz
2021-06-15 17:41 ` Paolo Bonzini
2021-06-03 13:37 ` Paolo Bonzini [this message]
2021-06-03 17:33 ` [PATCH v3 3/7] block: add max_hw_transfer to BlockLimits Eric Blake
2021-06-04 7:21 ` Paolo Bonzini
2021-06-15 16:18 ` Max Reitz
2021-06-16 13:18 ` Paolo Bonzini
2021-06-16 13:46 ` Max Reitz
2021-06-17 9:59 ` Paolo Bonzini
2021-06-03 13:37 ` [PATCH v3 4/7] file-posix: try BLKSECTGET on block devices too, do not round to power of 2 Paolo Bonzini
2021-06-15 16:32 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 5/7] block: feature detection for host block support Paolo Bonzini
2021-06-15 16:40 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 6/7] block: check for sys/disk.h Paolo Bonzini
2021-06-15 16:42 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 7/7] block: detect DKIOCGETBLOCKCOUNT/SIZE before use Paolo Bonzini
2021-06-15 16:50 ` Max Reitz
2021-06-15 16:57 ` Daniel P. Berrangé
2021-06-07 13:52 ` [PATCH v3 0/7] block: file-posix queue Maxim Levitsky
2021-06-10 13:40 ` Paolo Bonzini
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