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e9f4550b74
On macOS we need to increase unix socket buffers size on the client and
server to get good performance. We set socket buffers on macOS after
connecting or accepting a client connection.
Testing shows that setting socket receive buffer size (SO_RCVBUF) has no
effect on performance, so we set only the send buffer size (SO_SNDBUF).
It seems to work like Linux but not documented.
Testing shows that optimal buffer size is 512k to 4 MiB, depending on
the test case. The difference is very small, so I chose 2 MiB.
I tested reading from qemu-nbd and writing to qemu-nbd with qemu-img and
computing a blkhash with nbdcopy and blksum.
To focus on NBD communication and get less noisy results, I tested
reading and writing to null-co driver. I added a read-pattern option to
the null-co driver to return data full of 0xff:
NULL="json:{'driver': 'raw', 'file': {'driver': 'null-co', 'size': '10g', 'read-pattern': 255}}"
For testing buffer size I added an environment variable for setting the
socket buffer size.
Read from qemu-nbd via qemu-img convert. In this test buffer size of 2m
is optimal (12.6 times faster).
qemu-nbd -r -t -e 0 -f raw -k /tmp/nbd.sock "$NULL" &
qemu-img convert -f raw -O raw -W -n "nbd+unix:///?socket=/tmp/nbd.sock" "$NULL"
| buffer size | time | user | system |
|-------------|---------|---------|---------|
| default | 13.361 | 2.653 | 5.702 |
| 65536 | 2.283 | 0.204 | 1.318 |
| 131072 | 1.673 | 0.062 | 1.008 |
| 262144 | 1.592 | 0.053 | 0.952 |
| 524288 | 1.496 | 0.049 | 0.887 |
| 1048576 | 1.234 | 0.047 | 0.738 |
| 2097152 | 1.060 | 0.080 | 0.602 |
| 4194304 | 1.061 | 0.076 | 0.604 |
Write to qemu-nbd with qemu-img convert. In this test buffer size of 2m
is optimal (9.2 times faster).
qemu-nbd -t -e 0 -f raw -k /tmp/nbd.sock "$NULL" &
qemu-img convert -f raw -O raw -W -n "$NULL" "nbd+unix:///?socket=/tmp/nbd.sock"
| buffer size | time | user | system |
|-------------|---------|---------|---------|
| default | 8.063 | 2.522 | 4.184 |
| 65536 | 1.472 | 0.430 | 0.867 |
| 131072 | 1.071 | 0.297 | 0.654 |
| 262144 | 1.012 | 0.239 | 0.587 |
| 524288 | 0.970 | 0.201 | 0.514 |
| 1048576 | 0.895 | 0.184 | 0.454 |
| 2097152 | 0.877 | 0.174 | 0.440 |
| 4194304 | 0.944 | 0.231 | 0.535 |
Compute a blkhash with nbdcopy, using 4 NBD connections and 256k request
size. In this test buffer size of 4m is optimal (5.1 times faster).
qemu-nbd -r -t -e 0 -f raw -k /tmp/nbd.sock "$NULL" &
nbdcopy --blkhash "nbd+unix:///?socket=/tmp/nbd.sock" null:
| buffer size | time | user | system |
|-------------|---------|---------|---------|
| default | 8.624 | 5.727 | 6.507 |
| 65536 | 2.563 | 4.760 | 2.498 |
| 131072 | 1.903 | 4.559 | 2.093 |
| 262144 | 1.759 | 4.513 | 1.935 |
| 524288 | 1.729 | 4.489 | 1.924 |
| 1048576 | 1.696 | 4.479 | 1.884 |
| 2097152 | 1.710 | 4.480 | 1.763 |
| 4194304 | 1.687 | 4.479 | 1.712 |
Compute a blkhash with blksum, using 1 NBD connection and 256k read
size. In this test buffer size of 512k is optimal (10.3 times faster).
qemu-nbd -r -t -e 0 -f raw -k /tmp/nbd.sock "$NULL" &
blksum "nbd+unix:///?socket=/tmp/nbd.sock"
| buffer size | time | user | system |
|-------------|---------|---------|---------|
| default | 13.085 | 5.664 | 6.461 |
| 65536 | 3.299 | 5.106 | 2.515 |
| 131072 | 2.396 | 4.989 | 2.069 |
| 262144 | 1.607 | 4.724 | 1.555 |
| 524288 | 1.271 | 4.528 | 1.224 |
| 1048576 | 1.294 | 4.565 | 1.333 |
| 2097152 | 1.299 | 4.569 | 1.344 |
| 4194304 | 1.291 | 4.559 | 1.327 |
Signed-off-by: Nir Soffer <nirsof@gmail.com>
Message-ID: <20250517201154.88456-3-nirsof@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
82 lines
2.5 KiB
C
82 lines
2.5 KiB
C
/*
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* NBD Internal Declarations
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*
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* Copyright Red Hat
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef NBD_INTERNAL_H
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#define NBD_INTERNAL_H
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#include "block/nbd.h"
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#include "system/block-backend.h"
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#include "io/channel-tls.h"
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#include "qemu/iov.h"
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#ifndef _WIN32
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#include <sys/ioctl.h>
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#endif
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#ifdef HAVE_SYS_IOCCOM_H
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#include <sys/ioccom.h>
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#endif
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#ifdef __linux__
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#include <linux/fs.h>
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#endif
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#include "qemu/bswap.h"
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/* This is all part of the "official" NBD API.
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*
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* The most up-to-date documentation is available at:
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* https://github.com/yoe/nbd/blob/master/doc/proto.md
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*/
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/* Size of all compact NBD_CMD_*, without payload */
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#define NBD_REQUEST_SIZE (4 + 2 + 2 + 8 + 8 + 4)
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/* Size of all extended NBD_CMD_*, without payload */
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#define NBD_EXTENDED_REQUEST_SIZE (4 + 2 + 2 + 8 + 8 + 8)
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/* Size of all NBD_REP_* sent in answer to most NBD_OPT_*, without payload */
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#define NBD_REPLY_SIZE (4 + 4 + 8)
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/* Size of reply to NBD_OPT_EXPORT_NAME */
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#define NBD_REPLY_EXPORT_NAME_SIZE (8 + 2 + 124)
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/* Size of oldstyle negotiation */
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#define NBD_OLDSTYLE_NEGOTIATE_SIZE (8 + 8 + 8 + 4 + 124)
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#define NBD_INIT_MAGIC 0x4e42444d41474943LL /* ASCII "NBDMAGIC" */
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#define NBD_OPTS_MAGIC 0x49484156454F5054LL /* ASCII "IHAVEOPT" */
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#define NBD_CLIENT_MAGIC 0x0000420281861253LL
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#define NBD_REP_MAGIC 0x0003e889045565a9LL
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#define NBD_SET_SOCK _IO(0xab, 0)
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#define NBD_SET_BLKSIZE _IO(0xab, 1)
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#define NBD_SET_SIZE _IO(0xab, 2)
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#define NBD_DO_IT _IO(0xab, 3)
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#define NBD_CLEAR_SOCK _IO(0xab, 4)
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#define NBD_CLEAR_QUE _IO(0xab, 5)
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#define NBD_PRINT_DEBUG _IO(0xab, 6)
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#define NBD_SET_SIZE_BLOCKS _IO(0xab, 7)
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#define NBD_DISCONNECT _IO(0xab, 8)
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#define NBD_SET_TIMEOUT _IO(0xab, 9)
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#define NBD_SET_FLAGS _IO(0xab, 10)
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/* nbd_write
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* Writes @size bytes to @ioc. Returns 0 on success.
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*/
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static inline int nbd_write(QIOChannel *ioc, const void *buffer, size_t size,
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Error **errp)
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{
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return qio_channel_write_all(ioc, buffer, size, errp) < 0 ? -EIO : 0;
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}
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int nbd_drop(QIOChannel *ioc, size_t size, Error **errp);
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/* nbd_set_socket_send_buffer
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* Set the socket send buffer size for optimal performance.
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*/
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void nbd_set_socket_send_buffer(QIOChannelSocket *sioc);
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#endif
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