"Liu, Yuan1" <yuan1....@intel.com> writes:
>> -----Original Message-----
>> From: Hao Xiang <hao.xi...@bytedance.com>
>> Sent: Saturday, January 6, 2024 7:53 AM
>> To: Fabiano Rosas <faro...@suse.de>
>> Cc: Bryan Zhang <bryan.zh...@bytedance.com>; qemu-devel@nongnu.org;
>> marcandre.lur...@redhat.com; pet...@redhat.com; quint...@redhat.com;
>> peter.mayd...@linaro.org; Liu, Yuan1 <yuan1....@intel.com>;
>> berra...@redhat.com
>> Subject: Re: [External] Re: [PATCH 3/5] migration: Introduce unimplemented
>> 'qatzip' compression method
>>
>> On Fri, Jan 5, 2024 at 12:07 PM Fabiano Rosas <faro...@suse.de> wrote:
>> >
>> > Bryan Zhang <bryan.zh...@bytedance.com> writes:
>> >
>> > +cc Yuan Liu, Daniel Berrangé
>> >
>> > > Adds support for 'qatzip' as an option for the multifd compression
>> > > method parameter, but copy-pastes the no-op logic to leave the
>> > > actual methods effectively unimplemented. This is in preparation of
>> > > a subsequent commit that will implement actually using QAT for
>> > > compression and decompression.
>> > >
>> > > Signed-off-by: Bryan Zhang <bryan.zh...@bytedance.com>
>> > > Signed-off-by: Hao Xiang <hao.xi...@bytedance.com>
>> > > ---
>> > > hw/core/qdev-properties-system.c | 6 ++-
>> > > migration/meson.build | 1 +
>> > > migration/multifd-qatzip.c | 81
>> ++++++++++++++++++++++++++++++++
>> > > migration/multifd.h | 1 +
>> > > qapi/migration.json | 5 +-
>> > > 5 files changed, 92 insertions(+), 2 deletions(-) create mode
>> > > 100644 migration/multifd-qatzip.c
>> > >
>> > > diff --git a/hw/core/qdev-properties-system.c
>> > > b/hw/core/qdev-properties-system.c
>> > > index 1a396521d5..d8e48dcb0e 100644
>> > > --- a/hw/core/qdev-properties-system.c
>> > > +++ b/hw/core/qdev-properties-system.c
>> > > @@ -658,7 +658,11 @@ const PropertyInfo qdev_prop_fdc_drive_type = {
>> > > const PropertyInfo qdev_prop_multifd_compression = {
>> > > .name = "MultiFDCompression",
>> > > .description = "multifd_compression values, "
>> > > - "none/zlib/zstd",
>> > > + "none/zlib/zstd"
>> > > +#ifdef CONFIG_QATZIP
>> > > + "/qatzip"
>> > > +#endif
>> > > + ,
>> > > .enum_table = &MultiFDCompression_lookup,
>> > > .get = qdev_propinfo_get_enum,
>> > > .set = qdev_propinfo_set_enum,
>> > > diff --git a/migration/meson.build b/migration/meson.build index
>> > > 92b1cc4297..e20f318379 100644
>> > > --- a/migration/meson.build
>> > > +++ b/migration/meson.build
>> > > @@ -40,6 +40,7 @@ if get_option('live_block_migration').allowed()
>> > > system_ss.add(files('block.c'))
>> > > endif
>> > > system_ss.add(when: zstd, if_true: files('multifd-zstd.c'))
>> > > +system_ss.add(when: qatzip, if_true: files('multifd-qatzip.c'))
>> > >
>> > > specific_ss.add(when: 'CONFIG_SYSTEM_ONLY',
>> > > if_true: files('ram.c', diff --git
>> > > a/migration/multifd-qatzip.c b/migration/multifd-qatzip.c new file
>> > > mode 100644 index 0000000000..1733bbddb7
>> > > --- /dev/null
>> > > +++ b/migration/multifd-qatzip.c
>> > > @@ -0,0 +1,81 @@
>> > > +/*
>> > > + * Multifd QATzip compression implementation
>> > > + *
>> > > + * Copyright (c) Bytedance
>> > > + *
>> > > + * Authors:
>> > > + * Bryan Zhang <bryan.zh...@bytedance.com>
>> > > + * Hao Xiang <hao.xi...@bytedance.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 "exec/ramblock.h"
>> > > +#include "exec/target_page.h"
>> > > +#include "qapi/error.h"
>> > > +#include "migration.h"
>> > > +#include "options.h"
>> > > +#include "multifd.h"
>> > > +
>> > > +static int qatzip_send_setup(MultiFDSendParams *p, Error **errp) {
>> > > + return 0;
>> > > +}
>> > > +
>> > > +static void qatzip_send_cleanup(MultiFDSendParams *p, Error **errp)
>> > > +{};
>> > > +
>> > > +static int qatzip_send_prepare(MultiFDSendParams *p, Error **errp)
>> > > +{
>> > > + MultiFDPages_t *pages = p->pages;
>> > > +
>> > > + for (int i = 0; i < p->normal_num; i++) {
>> > > + p->iov[p->iovs_num].iov_base = pages->block->host + p-
>> >normal[i];
>> > > + p->iov[p->iovs_num].iov_len = p->page_size;
>> > > + p->iovs_num++;
>> > > + }
>> > > +
>> > > + p->next_packet_size = p->normal_num * p->page_size;
>> > > + p->flags |= MULTIFD_FLAG_NOCOMP;
>> > > + return 0;
>> > > +}
>> > > +
>> > > +static int qatzip_recv_setup(MultiFDRecvParams *p, Error **errp) {
>> > > + return 0;
>> > > +}
>> > > +
>> > > +static void qatzip_recv_cleanup(MultiFDRecvParams *p) {};
>> > > +
>> > > +static int qatzip_recv_pages(MultiFDRecvParams *p, Error **errp) {
>> > > + uint32_t flags = p->flags & MULTIFD_FLAG_COMPRESSION_MASK;
>> > > +
>> > > + if (flags != MULTIFD_FLAG_NOCOMP) {
>> > > + error_setg(errp, "multifd %u: flags received %x flags
>> expected %x",
>> > > + p->id, flags, MULTIFD_FLAG_NOCOMP);
>> > > + return -1;
>> > > + }
>> > > + for (int i = 0; i < p->normal_num; i++) {
>> > > + p->iov[i].iov_base = p->host + p->normal[i];
>> > > + p->iov[i].iov_len = p->page_size;
>> > > + }
>> > > + return qio_channel_readv_all(p->c, p->iov, p->normal_num,
>> > > +errp); }
>> > > +
>> > > +static MultiFDMethods multifd_qatzip_ops = {
>> > > + .send_setup = qatzip_send_setup,
>> > > + .send_cleanup = qatzip_send_cleanup,
>> > > + .send_prepare = qatzip_send_prepare,
>> > > + .recv_setup = qatzip_recv_setup,
>> > > + .recv_cleanup = qatzip_recv_cleanup,
>> > > + .recv_pages = qatzip_recv_pages };
>> > > +
>> > > +static void multifd_qatzip_register(void) {
>> > > + multifd_register_ops(MULTIFD_COMPRESSION_QATZIP,
>> > > +&multifd_qatzip_ops); }
>> > > +
>> > > +migration_init(multifd_qatzip_register);
>> > > diff --git a/migration/multifd.h b/migration/multifd.h index
>> > > a835643b48..5600f7fc82 100644
>> > > --- a/migration/multifd.h
>> > > +++ b/migration/multifd.h
>> > > @@ -33,6 +33,7 @@ int multifd_queue_page(QEMUFile *f, RAMBlock
>> > > *block, ram_addr_t offset); #define MULTIFD_FLAG_NOCOMP (0 << 1)
>> > > #define MULTIFD_FLAG_ZLIB (1 << 1) #define MULTIFD_FLAG_ZSTD (2 <<
>> > > 1)
>> > > +#define MULTIFD_FLAG_QATZIP (3 << 1)
>> > >
>> > > /* This value needs to be a multiple of qemu_target_page_size() */
>> > > #define MULTIFD_PACKET_SIZE (512 * 1024) diff --git
>> > > a/qapi/migration.json b/qapi/migration.json index
>> > > 6d5a4b0489..e3cc195aed 100644
>> > > --- a/qapi/migration.json
>> > > +++ b/qapi/migration.json
>> > > @@ -625,11 +625,14 @@
>> > > #
>> > > # @zstd: use zstd compression method.
>> > > #
>> > > +# @qatzip: use qatzip compression method.
>> > > +#
>> > > # Since: 5.0
>> > > ##
>> > > { 'enum': 'MultiFDCompression',
>> > > 'data': [ 'none', 'zlib',
>> > > - { 'name': 'zstd', 'if': 'CONFIG_ZSTD' } ] }
>> > > + { 'name': 'zstd', 'if': 'CONFIG_ZSTD' },
>> > > + { 'name': 'qatzip', 'if': 'CONFIG_QATZIP'} ] }
>> >
>> > In another thread adding support to another Intel accelerator (IAA) we
>> > decided that it was better to select the offloading as an accelerator
>> > method to multifd zlib rather than as an entirely new compression
>> > format. Take a look at that discussion:
>> > https://lore.kernel.org/r/ztfcnqbbqlmsu...@redhat.com
>>
>> We had some early discussion with Intel folks (probably a different team
>> than the one with the above patchset). The understanding at the time is
>> that QAT is good at both bulk data compression and decompression. IAA is
>> good at decompression with smaller data size but compression performance
>> is not the best. In multifd, we are compressing up to 128 4k pages at a
>> time and potentially this can increase by configuring the packet size, at
>> the time we thought QAT could be a better fit in the multifd live
>> migration scenario. We would like to hear more from Intel.
>>
>> From our benchmark testing, with two QAT devices, we can get deflate
>> compression throughout to around 7GB/s with ~160% CPU. That's beating the
>> current software implementation (zlib and zstd) by a lot. We are still
>> tuning the configuration in QEMU live migration now.
>>
>> >
>> > As I understand it, QAT + QATzip would be compatible with both zlib
>> > and IAA + QPL, so we'd add another accelerator method like this:
>> >
>> > https://lore.kernel.org/r/20240103112851.908082-3-yuan1....@intel.com
>> >
>>
>> I quickly read over the IAA patchset and I saw this:
>>
>> "However, due to some reasons, QPL is currently not compatible with the
>> existing Zlib method that Zlib compressed data can be decompressed by QPl
>> and vice versa."
>>
>> The above probably means the current zlib software implementation and IAA
>> are not compatible.
>>
>> For QAT, although, both Intel's QATzip and zlib are internally using
>> deflate, QATzip only supports deflate with a 4 byte header, deflate
>> wrapped by Gzip header and footer, or deflate wrapped by Intel® QAT
>> Gzip* extension header and footer. None of the headers can be recognized
>> by zlib software implementation is my understanding. So if we want to make
>> them compatible with zlib, the QATzip library needs to support that.
>
> The QPL library currently cannot support the Z_SYNC_FLULSH operation of zlib
> steaming.
> This is the reason why it is not compatible with zlib.
>
I had understood from previous discussion that we'd be able to at least
support compression with QPL and decompression with the existing
zlib-based code. Is that not correct? I was about to suggest
experimenting with the window size in the existing code to hopefully
solve the 4kb window size issue. If there are other limitations, then
that will not be enough.
Also, can you point to the source of that statement about Z_SYNC_FLUSH,
I couldn't find more information about it in the documentation.
>> > All that, of course, assuming we even want to support both
>> > accelerators. They're addressing the same problem after all. I wonder
>> > how we'd choose a precedence, since both seem to be present in the
>> > same processor family.
>> >
>> >
>>
>> That's an interesting question :-) I think overall performance (throughput
>> and CPU overhead) should both be considered. IAA and QAT accelerators
>> don't present on all systems. We Bytedance choose to have both on our
>> platform when purchasing from Intel.
