From 3a20013fbb26d2a1bd11ef148eefdb1508783787 Mon Sep 17 00:00:00 2001 From: Nir Soffer Date: Tue, 27 Aug 2019 04:05:27 +0300 Subject: block: posix: Always allocate the first block When creating an image with preallocation "off" or "falloc", the first block of the image is typically not allocated. When using Gluster storage backed by XFS filesystem, reading this block using direct I/O succeeds regardless of request length, fooling alignment detection. In this case we fallback to a safe value (4096) instead of the optimal value (512), which may lead to unneeded data copying when aligning requests. Allocating the first block avoids the fallback. Since we allocate the first block even with preallocation=off, we no longer create images with zero disk size: $ ./qemu-img create -f raw test.raw 1g Formatting 'test.raw', fmt=raw size=1073741824 $ ls -lhs test.raw 4.0K -rw-r--r--. 1 nsoffer nsoffer 1.0G Aug 16 23:48 test.raw And converting the image requires additional cluster: $ ./qemu-img measure -f raw -O qcow2 test.raw required size: 458752 fully allocated size: 1074135040 When using format like vmdk with multiple files per image, we allocate one block per file: $ ./qemu-img create -f vmdk -o subformat=twoGbMaxExtentFlat test.vmdk 4g Formatting 'test.vmdk', fmt=vmdk size=4294967296 compat6=off hwversion=undefined subformat=twoGbMaxExtentFlat $ ls -lhs test*.vmdk 4.0K -rw-r--r--. 1 nsoffer nsoffer 2.0G Aug 27 03:23 test-f001.vmdk 4.0K -rw-r--r--. 1 nsoffer nsoffer 2.0G Aug 27 03:23 test-f002.vmdk 4.0K -rw-r--r--. 1 nsoffer nsoffer 353 Aug 27 03:23 test.vmdk I did quick performance test for copying disks with qemu-img convert to new raw target image to Gluster storage with sector size of 512 bytes: for i in $(seq 10); do rm -f dst.raw sleep 10 time ./qemu-img convert -f raw -O raw -t none -T none src.raw dst.raw done Here is a table comparing the total time spent: Type Before(s) After(s) Diff(%) --------------------------------------- real 530.028 469.123 -11.4 user 17.204 10.768 -37.4 sys 17.881 7.011 -60.7 We can see very clear improvement in CPU usage. Signed-off-by: Nir Soffer Message-id: 20190827010528.8818-2-nsoffer@redhat.com Reviewed-by: Max Reitz Signed-off-by: Max Reitz --- tests/qemu-iotests/059.out | 2 +- tests/qemu-iotests/150.out | 11 ----------- tests/qemu-iotests/150.out.qcow2 | 11 +++++++++++ tests/qemu-iotests/150.out.raw | 12 ++++++++++++ tests/qemu-iotests/175 | 19 +++++++++++++------ tests/qemu-iotests/175.out | 8 ++++---- tests/qemu-iotests/178.out.qcow2 | 4 ++-- tests/qemu-iotests/221.out | 12 ++++++++---- tests/qemu-iotests/253.out | 12 ++++++++---- 9 files changed, 59 insertions(+), 32 deletions(-) delete mode 100644 tests/qemu-iotests/150.out create mode 100644 tests/qemu-iotests/150.out.qcow2 create mode 100644 tests/qemu-iotests/150.out.raw (limited to 'tests') diff --git a/tests/qemu-iotests/059.out b/tests/qemu-iotests/059.out index 4fab42a..fe3f861 100644 --- a/tests/qemu-iotests/059.out +++ b/tests/qemu-iotests/059.out @@ -27,7 +27,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824000 subformat=twoGbMax image: TEST_DIR/t.vmdk file format: vmdk virtual size: 0.977 TiB (1073741824000 bytes) -disk size: 16 KiB +disk size: 1.97 MiB Format specific information: cid: XXXXXXXX parent cid: XXXXXXXX diff --git a/tests/qemu-iotests/150.out b/tests/qemu-iotests/150.out deleted file mode 100644 index 2a54e8d..0000000 --- a/tests/qemu-iotests/150.out +++ /dev/null @@ -1,11 +0,0 @@ -QA output created by 150 - -=== Mapping sparse conversion === - -Offset Length File - -=== Mapping non-sparse conversion === - -Offset Length File -0 0x100000 TEST_DIR/t.IMGFMT -*** done diff --git a/tests/qemu-iotests/150.out.qcow2 b/tests/qemu-iotests/150.out.qcow2 new file mode 100644 index 0000000..2a54e8d --- /dev/null +++ b/tests/qemu-iotests/150.out.qcow2 @@ -0,0 +1,11 @@ +QA output created by 150 + +=== Mapping sparse conversion === + +Offset Length File + +=== Mapping non-sparse conversion === + +Offset Length File +0 0x100000 TEST_DIR/t.IMGFMT +*** done diff --git a/tests/qemu-iotests/150.out.raw b/tests/qemu-iotests/150.out.raw new file mode 100644 index 0000000..3cdc772 --- /dev/null +++ b/tests/qemu-iotests/150.out.raw @@ -0,0 +1,12 @@ +QA output created by 150 + +=== Mapping sparse conversion === + +Offset Length File +0 0x1000 TEST_DIR/t.IMGFMT + +=== Mapping non-sparse conversion === + +Offset Length File +0 0x100000 TEST_DIR/t.IMGFMT +*** done diff --git a/tests/qemu-iotests/175 b/tests/qemu-iotests/175 index 51e62c8..7ba28b3 100755 --- a/tests/qemu-iotests/175 +++ b/tests/qemu-iotests/175 @@ -37,14 +37,16 @@ trap "_cleanup; exit \$status" 0 1 2 3 15 # the file size. This function hides the resulting difference in the # stat -c '%b' output. # Parameter 1: Number of blocks an empty file occupies -# Parameter 2: Image size in bytes +# Parameter 2: Minimal number of blocks in an image +# Parameter 3: Image size in bytes _filter_blocks() { extra_blocks=$1 - img_size=$2 + min_blocks=$2 + img_size=$3 - sed -e "s/blocks=$extra_blocks\\(\$\\|[^0-9]\\)/nothing allocated/" \ - -e "s/blocks=$((extra_blocks + img_size / 512))\\(\$\\|[^0-9]\\)/everything allocated/" + sed -e "s/blocks=$min_blocks\\(\$\\|[^0-9]\\)/min allocation/" \ + -e "s/blocks=$((extra_blocks + img_size / 512))\\(\$\\|[^0-9]\\)/max allocation/" } # get standard environment, filters and checks @@ -60,16 +62,21 @@ size=$((1 * 1024 * 1024)) touch "$TEST_DIR/empty" extra_blocks=$(stat -c '%b' "$TEST_DIR/empty") +# We always write the first byte; check how many blocks this filesystem +# allocates to match empty image alloation. +printf "\0" > "$TEST_DIR/empty" +min_blocks=$(stat -c '%b' "$TEST_DIR/empty") + echo echo "== creating image with default preallocation ==" _make_test_img $size | _filter_imgfmt -stat -c "size=%s, blocks=%b" $TEST_IMG | _filter_blocks $extra_blocks $size +stat -c "size=%s, blocks=%b" $TEST_IMG | _filter_blocks $extra_blocks $min_blocks $size for mode in off full falloc; do echo echo "== creating image with preallocation $mode ==" IMGOPTS=preallocation=$mode _make_test_img $size | _filter_imgfmt - stat -c "size=%s, blocks=%b" $TEST_IMG | _filter_blocks $extra_blocks $size + stat -c "size=%s, blocks=%b" $TEST_IMG | _filter_blocks $extra_blocks $min_blocks $size done # success, all done diff --git a/tests/qemu-iotests/175.out b/tests/qemu-iotests/175.out index 6d9a5ed..263e521 100644 --- a/tests/qemu-iotests/175.out +++ b/tests/qemu-iotests/175.out @@ -2,17 +2,17 @@ QA output created by 175 == creating image with default preallocation == Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 -size=1048576, nothing allocated +size=1048576, min allocation == creating image with preallocation off == Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 preallocation=off -size=1048576, nothing allocated +size=1048576, min allocation == creating image with preallocation full == Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 preallocation=full -size=1048576, everything allocated +size=1048576, max allocation == creating image with preallocation falloc == Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 preallocation=falloc -size=1048576, everything allocated +size=1048576, max allocation *** done diff --git a/tests/qemu-iotests/178.out.qcow2 b/tests/qemu-iotests/178.out.qcow2 index 55a8dc9..9e7d8c4 100644 --- a/tests/qemu-iotests/178.out.qcow2 +++ b/tests/qemu-iotests/178.out.qcow2 @@ -101,7 +101,7 @@ converted image file size in bytes: 196608 == raw input image with data (human) == Formatting 'TEST_DIR/t.qcow2', fmt=IMGFMT size=1073741824 -required size: 393216 +required size: 458752 fully allocated size: 1074135040 wrote 512/512 bytes at offset 512 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) @@ -257,7 +257,7 @@ converted image file size in bytes: 196608 Formatting 'TEST_DIR/t.qcow2', fmt=IMGFMT size=1073741824 { - "required": 393216, + "required": 458752, "fully-allocated": 1074135040 } wrote 512/512 bytes at offset 512 diff --git a/tests/qemu-iotests/221.out b/tests/qemu-iotests/221.out index 9f9dd52..dca024a 100644 --- a/tests/qemu-iotests/221.out +++ b/tests/qemu-iotests/221.out @@ -3,14 +3,18 @@ QA output created by 221 === Check mapping of unaligned raw image === Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=65537 -[{ "start": 0, "length": 66048, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] -[{ "start": 0, "length": 66048, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 61952, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 61952, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] wrote 1/1 bytes at offset 65536 1 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) -[{ "start": 0, "length": 65536, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 61440, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, { "start": 65536, "length": 1, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, { "start": 65537, "length": 511, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] -[{ "start": 0, "length": 65536, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 61440, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, { "start": 65536, "length": 1, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, { "start": 65537, "length": 511, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] *** done diff --git a/tests/qemu-iotests/253.out b/tests/qemu-iotests/253.out index 607c0ba..3d08b30 100644 --- a/tests/qemu-iotests/253.out +++ b/tests/qemu-iotests/253.out @@ -3,12 +3,16 @@ QA output created by 253 === Check mapping of unaligned raw image === Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048575 -[{ "start": 0, "length": 1048576, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] -[{ "start": 0, "length": 1048576, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 1044480, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 1044480, "depth": 0, "zero": true, "data": false, "offset": OFFSET}] wrote 65535/65535 bytes at offset 983040 63.999 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) -[{ "start": 0, "length": 983040, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 978944, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, { "start": 983040, "length": 65536, "depth": 0, "zero": false, "data": true, "offset": OFFSET}] -[{ "start": 0, "length": 983040, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, +[{ "start": 0, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET}, +{ "start": 4096, "length": 978944, "depth": 0, "zero": true, "data": false, "offset": OFFSET}, { "start": 983040, "length": 65536, "depth": 0, "zero": false, "data": true, "offset": OFFSET}] *** done -- cgit v1.1