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[Qemu-devel] [PATCH 2/3] block: do not allocate an iovec per read of a g
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 2/3] block: do not allocate an iovec per read of a growable/zero_after_eof BDS |
Date: |
Wed, 17 Dec 2014 16:09:59 +0100 |
Most reads do not go past the end of the file, and they can use the
input QEMUIOVector instead of creating one. This removes the
qemu_iovec_* functions from the profile.
Signed-off-by: Paolo Bonzini <address@hidden>
---
block.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/block.c b/block.c
index 4165d42..58f8042 100644
--- a/block.c
+++ b/block.c
@@ -3034,18 +3034,16 @@ static int coroutine_fn
bdrv_aligned_preadv(BlockDriverState *bs,
max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num),
align >> BDRV_SECTOR_BITS);
- if (max_nb_sectors > 0) {
+ if (nb_sectors < max_nb_sectors) {
+ ret = drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
+ } else if (max_nb_sectors > 0) {
QEMUIOVector local_qiov;
- size_t local_sectors;
-
- max_nb_sectors = MIN(max_nb_sectors, SIZE_MAX / BDRV_SECTOR_BITS);
- local_sectors = MIN(max_nb_sectors, nb_sectors);
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, 0,
- local_sectors * BDRV_SECTOR_SIZE);
+ max_nb_sectors * BDRV_SECTOR_SIZE);
- ret = drv->bdrv_co_readv(bs, sector_num, local_sectors,
+ ret = drv->bdrv_co_readv(bs, sector_num, max_nb_sectors,
&local_qiov);
qemu_iovec_destroy(&local_qiov);
--
2.1.0