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[Qemu-block] [PATCH v2 02/12] util/iov: improve qemu_iovec_is_zero
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[Qemu-block] [PATCH v2 02/12] util/iov: improve qemu_iovec_is_zero |
Date: |
Tue, 4 Jun 2019 19:15:04 +0300 |
We'll need to check a part of qiov soon, so implement it now.
Optimization with align down to 4 * sizeof(long) is dropped due to:
1. It is strange: it aligns length of the buffer, but where is a
guarantee that buffer pointer is aligned itself?
2. buffer_is_zero() is a better place for optimizations and it has
them.
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
include/qemu/iov.h | 2 +-
block/io.c | 2 +-
util/iov.c | 31 +++++++++++++++++++------------
3 files changed, 21 insertions(+), 14 deletions(-)
diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index f3787a0cf7..29957c8a72 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -212,7 +212,7 @@ void qemu_iovec_concat(QEMUIOVector *dst,
size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
struct iovec *src_iov, unsigned int src_cnt,
size_t soffset, size_t sbytes);
-bool qemu_iovec_is_zero(QEMUIOVector *qiov);
+bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t qiov_offeset, size_t bytes);
void qemu_iovec_destroy(QEMUIOVector *qiov);
void qemu_iovec_reset(QEMUIOVector *qiov);
size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
diff --git a/block/io.c b/block/io.c
index 3134a60a48..d02fded3b1 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1651,7 +1651,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild
*child,
if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
!(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
- qemu_iovec_is_zero(qiov)) {
+ qemu_iovec_is_zero(qiov, 0, qiov->size)) {
flags |= BDRV_REQ_ZERO_WRITE;
if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
flags |= BDRV_REQ_MAY_UNMAP;
diff --git a/util/iov.c b/util/iov.c
index 39b6e31494..d988a533ce 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -451,23 +451,30 @@ void qemu_iovec_init_extended(
}
/*
- * Check if the contents of the iovecs are all zero
+ * Check if the contents of subrange of qiov data is all zeroes.
*/
-bool qemu_iovec_is_zero(QEMUIOVector *qiov)
+bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes)
{
- int i;
- for (i = 0; i < qiov->niov; i++) {
- size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
- uint8_t *ptr = qiov->iov[i].iov_base;
- if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
+ struct iovec *iov;
+ size_t current_offset;
+
+ assert(offset + bytes <= qiov->size);
+
+ iov = iov_skip_offset(qiov->iov, offset, ¤t_offset);
+
+ while (bytes) {
+ uint8_t *base = (uint8_t *)iov->iov_base + current_offset;
+ size_t len = MIN(iov->iov_len - current_offset, bytes);
+
+ if (!buffer_is_zero(base, len)) {
return false;
}
- for (; offs < qiov->iov[i].iov_len; offs++) {
- if (ptr[offs]) {
- return false;
- }
- }
+
+ current_offset = 0;
+ bytes -= len;
+ iov++;
}
+
return true;
}
--
2.18.0
- [Qemu-block] [PATCH v2 00/12] block: qiov_offset parameter for io, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 12/12] block/qcow2: implement .bdrv_co_pwritev(_compressed)_part, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 10/12] block/qcow2: refactor qcow2_co_preadv to use buffer-based io, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 08/12] block/io: bdrv_aligned_pwritev: use and support qiov_offset, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 07/12] block/io: bdrv_aligned_preadv: use and support qiov_offset, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 06/12] block/io: bdrv_co_do_copy_on_readv: lazy allocation, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_extended, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 02/12] util/iov: improve qemu_iovec_is_zero,
Vladimir Sementsov-Ogievskiy <=
- [Qemu-block] [PATCH v2 05/12] block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 11/12] block/qcow2: implement .bdrv_co_preadv_part, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 04/12] block: define .*_part io handlers in BlockDriver, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 03/12] block/io: refactor padding, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 09/12] block/io: introduce bdrv_co_p{read, write}v_part, Vladimir Sementsov-Ogievskiy, 2019/06/04
- Re: [Qemu-block] [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io, no-reply, 2019/06/05
- Re: [Qemu-block] [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io, Stefan Hajnoczi, 2019/06/28