Re: [PATCH v3 19/21] migration: Add zlib compression multifd support

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  hw/core/qdev-properties.c    |   2 +-
>  migration/Makefile.objs      |   1 +
>  migration/multifd-zlib.c     | 289 +++++++++++++++++++++++++++++++++++
>  migration/multifd.c          |   6 +
>  migration/multifd.h          |   4 +
>  qapi/migration.json          |   2 +-
>  tests/qtest/migration-test.c |   6 +
>  7 files changed, 308 insertions(+), 2 deletions(-)
>  create mode 100644 migration/multifd-zlib.c
> 
> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index ff6a752b19..07ec75d8e3 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -647,7 +647,7 @@ const PropertyInfo qdev_prop_fdc_drive_type = {
>  const PropertyInfo qdev_prop_multifd_compress = {
>      .name = "MultifdCompress",
>      .description = "multifd_compress values, "
> -                   "none",
> +                   "none/zlib",
>      .enum_table = &MultifdCompress_lookup,
>      .get = get_enum,
>      .set = set_enum,
> diff --git a/migration/Makefile.objs b/migration/Makefile.objs
> index d3623d5f9b..0308caa5c5 100644
> --- a/migration/Makefile.objs
> +++ b/migration/Makefile.objs
> @@ -8,6 +8,7 @@ common-obj-y += xbzrle.o postcopy-ram.o
>  common-obj-y += qjson.o
>  common-obj-y += block-dirty-bitmap.o
>  common-obj-y += multifd.o
> +common-obj-y += multifd-zlib.o
>  
>  common-obj-$(CONFIG_RDMA) += rdma.o
>  
> diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
> new file mode 100644
> index 0000000000..33d7ee6741
> --- /dev/null
> +++ b/migration/multifd-zlib.c
> @@ -0,0 +1,289 @@
> +/*
> + * Multifd zlib compression implementation
> + *
> + * Copyright (c) 2020 Red Hat Inc
> + *
> + * Authors:
> + *  Juan Quintela <quintela@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include <zlib.h>
> +#include "qemu/rcu.h"
> +#include "exec/target_page.h"
> +#include "qapi/error.h"
> +#include "migration.h"
> +#include "trace.h"
> +#include "multifd.h"
> +
> +struct zlib_data {
> +    /* stream for compression */
> +    z_stream zs;
> +    /* compressed buffer */
> +    uint8_t *zbuff;
> +    /* size of compressed buffer */
> +    uint32_t zbuff_len;
> +};
> +
> +/* Multifd zlib compression */
> +
> +/**
> + * zlib_send_setup: setup send side
> + *
> + * Setup each channel with zlib compression.
> + *
> + * Returns 0 for success or -1 for error
> + *
> + * @p: Params for the channel that we are using
> + * @errp: pointer to an error
> + */
> +static int zlib_send_setup(MultiFDSendParams *p, Error **errp)
> +{
> +    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
> +    struct zlib_data *z = g_malloc0(sizeof(struct zlib_data));
> +    z_stream *zs = &z->zs;
> +
> +    p->data = z;
> +    zs->zalloc = Z_NULL;
> +    zs->zfree = Z_NULL;
> +    zs->opaque = Z_NULL;
> +    if (deflateInit(zs, migrate_compress_level()) != Z_OK) {
> +        g_free(z);
> +        error_setg(errp, "multifd %d: deflate init failed", p->id);
> +        return -1;
> +    }
> +    /* We will never have more than page_count pages */
> +    z->zbuff_len = page_count * qemu_target_page_size();
> +    z->zbuff_len *= 2;
> +    z->zbuff = g_try_malloc(z->zbuff_len);
> +    if (!z->zbuff) {

Does a deflateEnd need to be called here?

> +        g_free(z);
> +        error_setg(errp, "multifd %d: out of memory for zbuff", p->id);
> +        return -1;
> +    }
> +    return 0;

I'd like to understand more aobut the failure path - lets say we exit
through one of those return -1's, p->data is still set to point to z
which is now been free'd.  Will zlib_send_cleanup get called?
Maybe it's safer to move the 'p->data = z' to right at the bottom before
the return 0 ?

> +}
> +
> +/**
> + * zlib_send_cleanup: cleanup send side
> + *
> + * Close the channel and return memory.
> + *
> + * @p: Params for the channel that we are using
> + */
> +static void zlib_send_cleanup(MultiFDSendParams *p, Error **errp)
> +{
> +    struct zlib_data *z = p->data;

As previously asked above, could this ever get called if zlib_send_setup
has failed? If so does this need to check for !z ?

> +    deflateEnd(&z->zs);
> +    g_free(z->zbuff);
> +    z->zbuff = NULL;
> +    g_free(p->data);
> +    p->data = NULL;
> +}
> +
> +/**
> + * zlib_send_prepare: prepare date to be able to send
> + *
> + * Create a compressed buffer with all the pages that we are going to
> + * send.
> + *
> + * Returns 0 for success or -1 for error
> + *
> + * @p: Params for the channel that we are using
> + * @used: number of pages used
> + */
> +static int zlib_send_prepare(MultiFDSendParams *p, uint32_t used, Error **errp)
> +{
> +    struct iovec *iov = p->pages->iov;
> +    struct zlib_data *z = p->data;
> +    z_stream *zs = &z->zs;
> +    uint32_t out_size = 0;
> +    int ret;
> +    uint32_t i;
> +
> +    for (i = 0; i < used; i++) {
> +        uint32_t available = z->zbuff_len - out_size;
> +        int flush = Z_NO_FLUSH;
> +
> +        if (i == used  - 1) {

Odd double space formatting there.

> +            flush = Z_SYNC_FLUSH;
> +        }
> +
> +        zs->avail_in = iov[i].iov_len;
> +        zs->next_in = iov[i].iov_base;
> +
> +        zs->avail_out = available;
> +        zs->next_out = z->zbuff + out_size;
> +
> +        ret = deflate(zs, flush);
> +        if (ret != Z_OK) {
> +            error_setg(errp, "multifd %d: deflate returned %d instead of Z_OK",
> +                       p->id, ret);
> +            return -1;
> +        }
> +        out_size += available - zs->avail_out;
> +    }
> +    p->next_packet_size = out_size;
> +    p->flags |= MULTIFD_FLAG_ZLIB;
> +
> +    return 0;
> +}
> +
> +/**
> + * zlib_send_write: do the actual write of the data
> + *
> + * Do the actual write of the comprresed buffer.
> + *
> + * Returns 0 for success or -1 for error
> + *
> + * @p: Params for the channel that we are using
> + * @used: number of pages used
> + * @errp: pointer to an error
> + */
> +static int zlib_send_write(MultiFDSendParams *p, uint32_t used, Error **errp)
> +{
> +    struct zlib_data *z = p->data;
> +
> +    return qio_channel_write_all(p->c, (void *)z->zbuff, p->next_packet_size,
> +                                 errp);
> +}
> +
> +/**
> + * zlib_recv_setup: setup receive side
> + *
> + * Create the compressed channel and buffer.
> + *
> + * Returns 0 for success or -1 for error
> + *
> + * @p: Params for the channel that we are using
> + * @errp: pointer to an error
> + */
> +static int zlib_recv_setup(MultiFDRecvParams *p, Error **errp)
> +{
> +    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
> +    struct zlib_data *z = g_malloc0(sizeof(struct zlib_data));
> +    z_stream *zs = &z->zs;
> +
> +    p->data = z;
> +    zs->zalloc = Z_NULL;
> +    zs->zfree = Z_NULL;
> +    zs->opaque = Z_NULL;
> +    zs->avail_in = 0;
> +    zs->next_in = Z_NULL;
> +    if (inflateInit(zs) != Z_OK) {
> +        error_setg(errp, "multifd %d: inflate init failed", p->id);
> +        return -1;
> +    }
> +    /* We will never have more than page_count pages */
> +    z->zbuff_len = page_count * qemu_target_page_size();
> +    /* We know compression "could" use more space */
> +    z->zbuff_len *= 2;
> +    z->zbuff = g_try_malloc(z->zbuff_len);
> +    if (!z->zbuff) {

inflateEnd and similar question to save?

> +        error_setg(errp, "multifd %d: out of memory for zbuff", p->id);
> +        return -1;
> +    }
> +    return 0;
> +}
> +
> +/**
> + * zlib_recv_cleanup: setup receive side
> + *
> + * For no compression this function does nothing.
> + *
> + * @p: Params for the channel that we are using
> + */
> +static void zlib_recv_cleanup(MultiFDRecvParams *p)
> +{
> +    struct zlib_data *z = p->data;
> +
> +    inflateEnd(&z->zs);
> +    g_free(z->zbuff);
> +    z->zbuff = NULL;
> +    g_free(p->data);
> +    p->data = NULL;
> +}
> +
> +/**
> + * zlib_recv_pages: read the data from the channel into actual pages
> + *
> + * Read the compressed buffer, and uncompress it into the actual
> + * pages.
> + *
> + * Returns 0 for success or -1 for error
> + *
> + * @p: Params for the channel that we are using
> + * @used: number of pages used
> + * @errp: pointer to an error
> + */
> +static int zlib_recv_pages(MultiFDRecvParams *p, uint32_t used, Error **errp)
> +{
> +    uint32_t in_size = p->next_packet_size;
> +    uint32_t out_size = 0;
> +    uint32_t expected_size = used * qemu_target_page_size();
> +    struct zlib_data *z = p->data;
> +    z_stream *zs = &z->zs;
> +    int ret;
> +    int i;
> +
> +    if (p->flags != MULTIFD_FLAG_ZLIB) {
> +        error_setg(errp, "multifd %d: flags received %x flags expected %x",
> +                   p->id, MULTIFD_FLAG_ZLIB, p->flags);
> +        return -1;
> +    }
> +    ret = qio_channel_read_all(p->c, (void *)z->zbuff, in_size, errp);
> +
> +    if (ret != 0) {
> +        return ret;
> +    }
> +
> +    zs->avail_in = in_size;
> +    zs->next_in = z->zbuff;
> +
> +    for (i = 0; i < used; i++) {
> +        struct iovec *iov = &p->pages->iov[i];
> +        int flush = Z_NO_FLUSH;
> +
> +        if (i == used  - 1) {
> +            flush = Z_SYNC_FLUSH;
> +        }
> +
> +        zs->avail_out = iov->iov_len;
> +        zs->next_out = iov->iov_base;
> +
> +        ret = inflate(zs, flush);
> +        if (ret != Z_OK) {
> +            error_setg(errp, "multifd %d: inflate returned %d instead of Z_OK",
> +                       p->id, ret);
> +            return ret;
> +        }
> +        out_size += iov->iov_len;

How do we know that's iov_len ?

> +    }
> +    if (out_size != expected_size) {
> +        error_setg(errp, "multifd %d: packet size received %d size expected %d",
> +                   p->id, out_size, expected_size);
> +        return -1;
> +    }
> +    return 0;
> +}
> +
> +static MultiFDMethods multifd_zlib_ops = {
> +    .send_setup = zlib_send_setup,
> +    .send_cleanup = zlib_send_cleanup,
> +    .send_prepare = zlib_send_prepare,
> +    .send_write = zlib_send_write,
> +    .recv_setup = zlib_recv_setup,
> +    .recv_cleanup = zlib_recv_cleanup,
> +    .recv_pages = zlib_recv_pages
> +};
> +
> +static void multifd_zlib_register(void)
> +{
> +    multifd_register_ops(MULTIFD_COMPRESS_ZLIB, &multifd_zlib_ops);
> +}
> +
> +migration_init(multifd_zlib_register);
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 353140cd25..a1fc451d49 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -164,6 +164,12 @@ static MultiFDMethods *multifd_ops[MULTIFD_COMPRESS__MAX] = {
>      [MULTIFD_COMPRESS_NONE] = &multifd_nocomp_ops,
>  };
>  
> +void multifd_register_ops(int method, MultiFDMethods *ops)
> +{
> +    assert(0 < method && method < MULTIFD_COMPRESS__MAX);
> +    multifd_ops[method] = ops;
> +}
> +
>  static int multifd_send_initial_packet(MultiFDSendParams *p, Error **errp)
>  {
>      MultiFDInit_t msg = {};
> diff --git a/migration/multifd.h b/migration/multifd.h
> index 8edea4fdac..85542f3222 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -23,8 +23,10 @@ void multifd_recv_sync_main(void);
>  void multifd_send_sync_main(QEMUFile *f);
>  int multifd_queue_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset);
>  
> +/* Multifd Compression flags */
>  #define MULTIFD_FLAG_SYNC (1 << 0)
>  #define MULTIFD_FLAG_NOCOMP (1 << 1)
> +#define MULTIFD_FLAG_ZLIB (1 << 2)
>  
>  /* This value needs to be a multiple of qemu_target_page_size() */
>  #define MULTIFD_PACKET_SIZE (512 * 1024)
> @@ -157,5 +159,7 @@ typedef struct {
>      int (*recv_pages)(MultiFDRecvParams *p, uint32_t used, Error **errp);
>  } MultiFDMethods;
>  
> +void multifd_register_ops(int method, MultiFDMethods *ops);
> +
>  #endif
>  
> diff --git a/qapi/migration.json b/qapi/migration.json
> index c2891e6ebf..1714ea51e3 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -499,7 +499,7 @@
>  #
>  ##
>  { 'enum': 'MultifdCompress',
> -  'data': [ 'none' ] }
> +  'data': [ 'none', 'zlib' ] }
>  
>  ##
>  # @MigrationParameter:
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index 3d5d2aba8c..985a7d4b97 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -1313,6 +1313,11 @@ static void test_multifd_tcp_none(void)
>      test_multifd_tcp("none");
>  }
>  
> +static void test_multifd_tcp_zlib(void)
> +{
> +    test_multifd_tcp("zlib");
> +}
> +
>  /*
>   * This test does:
>   *  source               target
> @@ -1475,6 +1480,7 @@ int main(int argc, char **argv)
>      qtest_add_func("/migration/auto_converge", test_migrate_auto_converge);
>      qtest_add_func("/migration/multifd/tcp/none", test_multifd_tcp_none);
>      qtest_add_func("/migration/multifd/tcp/cancel", test_multifd_tcp_cancel);
> +    qtest_add_func("/migration/multifd/tcp/zlib", test_multifd_tcp_zlib);
>  
>      ret = g_test_run();
>  
> -- 
> 2.24.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK