132 lines
5.4 KiB
Diff
132 lines
5.4 KiB
Diff
From 6773549977d94c504ec76aed67506ae85adff973 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 16 Jul 2021 16:51:33 -0400
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Subject: [PATCH 17/43] block: add max_hw_transfer to BlockLimits
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RH-Author: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Bugzilla: 1957194
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For block host devices, I/O can happen through either the kernel file
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descriptor I/O system calls (preadv/pwritev, io_submit, io_uring)
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or the SCSI passthrough ioctl SG_IO.
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In the latter case, the size of each transfer can be limited by the
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HBA, while for file descriptor I/O the kernel is able to split and
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merge I/O in smaller pieces as needed. Applying the HBA limits to
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file descriptor I/O results in more system calls and suboptimal
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performance, so this patch splits the max_transfer limit in two:
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max_transfer remains valid and is used in general, while max_hw_transfer
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is limited to the maximum hardware size. max_hw_transfer can then be
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included by the scsi-generic driver in the block limits page, to ensure
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that the stricter hardware limit is used.
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 24b36e9813ec15da7db62e3b3621730710c5f020)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/block-backend.c | 13 +++++++++++++
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block/file-posix.c | 2 +-
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block/io.c | 2 ++
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hw/scsi/scsi-generic.c | 2 +-
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include/block/block_int.h | 7 +++++++
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include/sysemu/block-backend.h | 1 +
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6 files changed, 25 insertions(+), 2 deletions(-)
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diff --git a/block/block-backend.c b/block/block-backend.c
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index 136cc602c5..b5f5b4b048 100644
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--- a/block/block-backend.c
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+++ b/block/block-backend.c
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@@ -1939,6 +1939,19 @@ uint32_t blk_get_request_alignment(BlockBackend *blk)
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return bs ? bs->bl.request_alignment : BDRV_SECTOR_SIZE;
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}
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+/* Returns the maximum hardware transfer length, in bytes; guaranteed nonzero */
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+uint64_t blk_get_max_hw_transfer(BlockBackend *blk)
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+{
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+ BlockDriverState *bs = blk_bs(blk);
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+ uint64_t max = INT_MAX;
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+
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+ if (bs) {
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+ max = MIN_NON_ZERO(max, bs->bl.max_hw_transfer);
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+ max = MIN_NON_ZERO(max, bs->bl.max_transfer);
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+ }
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+ return ROUND_DOWN(max, blk_get_request_alignment(blk));
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+}
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+
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/* Returns the maximum transfer length, in bytes; guaranteed nonzero */
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uint32_t blk_get_max_transfer(BlockBackend *blk)
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{
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diff --git a/block/file-posix.c b/block/file-posix.c
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index 1a6c799e19..44325a635d 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -1258,7 +1258,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
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int ret = sg_get_max_transfer_length(s->fd);
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if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
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- bs->bl.max_transfer = pow2floor(ret);
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+ bs->bl.max_hw_transfer = pow2floor(ret);
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}
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ret = sg_get_max_segments(s->fd);
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diff --git a/block/io.c b/block/io.c
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index ca2dca3007..a4b2e3adf1 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -126,6 +126,8 @@ static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
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{
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dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
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dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
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+ dst->max_hw_transfer = MIN_NON_ZERO(dst->max_hw_transfer,
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+ src->max_hw_transfer);
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dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
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src->opt_mem_alignment);
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dst->min_mem_alignment = MAX(dst->min_mem_alignment,
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diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
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index 82e1e2ee79..3762dce749 100644
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--- a/hw/scsi/scsi-generic.c
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+++ b/hw/scsi/scsi-generic.c
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@@ -179,7 +179,7 @@ static void scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s)
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(r->req.cmd.buf[1] & 0x01)) {
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page = r->req.cmd.buf[2];
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if (page == 0xb0) {
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- uint32_t max_transfer = blk_get_max_transfer(s->conf.blk);
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+ uint64_t max_transfer = blk_get_max_hw_transfer(s->conf.blk);
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uint32_t max_iov = blk_get_max_iov(s->conf.blk);
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assert(max_transfer);
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diff --git a/include/block/block_int.h b/include/block/block_int.h
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index 88e4111939..09d8630ec4 100644
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--- a/include/block/block_int.h
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+++ b/include/block/block_int.h
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@@ -695,6 +695,13 @@ typedef struct BlockLimits {
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* clamped down. */
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uint32_t max_transfer;
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+ /* Maximal hardware transfer length in bytes. Applies whenever
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+ * transfers to the device bypass the kernel I/O scheduler, for
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+ * example with SG_IO. If larger than max_transfer or if zero,
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+ * blk_get_max_hw_transfer will fall back to max_transfer.
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+ */
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+ uint64_t max_hw_transfer;
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+
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/* memory alignment, in bytes so that no bounce buffer is needed */
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size_t min_mem_alignment;
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diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
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index 5423e3d9c6..9ac5f7bbd3 100644
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--- a/include/sysemu/block-backend.h
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+++ b/include/sysemu/block-backend.h
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@@ -208,6 +208,7 @@ void blk_eject(BlockBackend *blk, bool eject_flag);
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int blk_get_flags(BlockBackend *blk);
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uint32_t blk_get_request_alignment(BlockBackend *blk);
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uint32_t blk_get_max_transfer(BlockBackend *blk);
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+uint64_t blk_get_max_hw_transfer(BlockBackend *blk);
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int blk_get_max_iov(BlockBackend *blk);
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void blk_set_guest_block_size(BlockBackend *blk, int align);
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void *blk_try_blockalign(BlockBackend *blk, size_t size);
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--
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2.27.0
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