RE: [PATCH 5/7] migration/multifd: Add UADK based compression and decompression

[Shameerali Kolothum Thodi via <qemu-devel@nongnu.org>]

> -----Original Message-----
> From: Fabiano Rosas <farosas@suse.de>
> Sent: Wednesday, June 5, 2024 7:57 PM
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> peterx@redhat.com; yuan1.liu@intel.com
> Cc: qemu-devel@nongnu.org; Linuxarm <linuxarm@huawei.com>; linwenkai
> (C) <linwenkai6@hisilicon.com>; zhangfei.gao@linaro.org; huangchenghai
> <huangchenghai2@huawei.com>
> Subject: Re: [PATCH 5/7] migration/multifd: Add UADK based compression
> and decompression
> 
> Shameer Kolothum via <qemu-devel@nongnu.org> writes:
> 
> > Uses UADK wd_do_comp_sync() API to (de)compress a normal page using
> > hardware accelerator.
> >
> > Signed-off-by: Shameer Kolothum
> <shameerali.kolothum.thodi@huawei.com>
> 
> A couple of comments below.
> 
> Reviewed-by: Fabiano Rosas <farosas@suse.de>
> > ---
> >  migration/multifd-uadk.c | 132
> ++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 130 insertions(+), 2 deletions(-)
> >
> > diff --git a/migration/multifd-uadk.c b/migration/multifd-uadk.c
> > index 3172e4d5ca..3329819bd4 100644
> > --- a/migration/multifd-uadk.c
> > +++ b/migration/multifd-uadk.c
> > @@ -13,6 +13,7 @@
> >  #include "qemu/osdep.h"
> >  #include "qemu/module.h"
> >  #include "qapi/error.h"
> > +#include "exec/ramblock.h"
> >  #include "migration.h"
> >  #include "multifd.h"
> >  #include "options.h"
> > @@ -140,6 +141,15 @@ static void
> multifd_uadk_send_cleanup(MultiFDSendParams *p, Error **errp)
> >      p->compress_data = NULL;
> >  }
> >
> > +static inline void prepare_next_iov(MultiFDSendParams *p, void *base,
> > +                                    uint32_t len)
> > +{
> > +    p->iov[p->iovs_num].iov_base = (uint8_t *)base;
> > +    p->iov[p->iovs_num].iov_len = len;
> > +    p->next_packet_size += len;
> > +    p->iovs_num++;
> > +}
> > +
> >  /**
> >   * multifd_uadk_send_prepare: prepare data to be able to send
> >   *
> > @@ -153,7 +163,56 @@ static void
> multifd_uadk_send_cleanup(MultiFDSendParams *p, Error **errp)
> >   */
> >  static int multifd_uadk_send_prepare(MultiFDSendParams *p, Error
> **errp)
> >  {
> > -    return -1;
> > +    struct wd_data *uadk_data = p->compress_data;
> > +    uint32_t hdr_size;
> > +    uint8_t *buf = uadk_data->buf;
> > +    int ret = 0;
> > +
> > +    if (!multifd_send_prepare_common(p)) {
> > +        goto out;
> > +    }
> > +
> > +    hdr_size = p->pages->normal_num * sizeof(uint32_t);
> > +    /* prepare the header that stores the lengths of all compressed data */
> > +    prepare_next_iov(p, uadk_data->buf_hdr, hdr_size);
> > +
> > +    for (int i = 0; i < p->pages->normal_num; i++) {
> > +        struct wd_comp_req creq = {
> > +            .op_type = WD_DIR_COMPRESS,
> > +            .src     = p->pages->block->host + p->pages->offset[i],
> > +            .src_len = p->page_size,
> > +            .dst     = buf,
> > +            /* Set dst_len to double the src to take care of -ve compression */
> 
> What's -ve compression?

Just meant the case where output is > input. I can reword this.

> 
> > +            .dst_len = p->page_size * 2,
> > +        };
> > +
> > +        ret = wd_do_comp_sync(uadk_data->handle, &creq);
> > +        if (ret || creq.status) {
> > +            error_setg(errp, "multifd %u: failed wd_do_comp_sync, ret %d
> status %d",
> > +                       p->id, ret, creq.status);
> > +            return -1;
> > +        }
> > +        if (creq.dst_len < p->page_size) {
> > +            uadk_data->buf_hdr[i] = cpu_to_be32(creq.dst_len);
> > +            prepare_next_iov(p, buf, creq.dst_len);
> > +            buf += creq.dst_len;
> > +        } else {
> > +            /*
> > +             * Send raw data if compressed out >= page_size. We might be
> better
> > +             * off sending raw data if output is slightly less than page_size
> > +             * as well because at the receive end we can skip the
> decompression.
> > +             * But it is tricky to find the right number here.
> > +             */
> > +            uadk_data->buf_hdr[i] = cpu_to_be32(p->page_size);
> > +            prepare_next_iov(p, p->pages->block->host + p->pages->offset[i],
> > +                             p->page_size);
> > +            buf += p->page_size;
> > +        }
> > +    }
> > +out:
> > +    p->flags |= MULTIFD_FLAG_UADK;
> > +    multifd_send_fill_packet(p);
> > +    return 0;
> >  }
> >
> >  /**
> > @@ -206,7 +265,76 @@ static void
> multifd_uadk_recv_cleanup(MultiFDRecvParams *p)
> >   */
> >  static int multifd_uadk_recv(MultiFDRecvParams *p, Error **errp)
> >  {
> > -    return -1;
> > +    struct wd_data *uadk_data = p->compress_data;
> > +    uint32_t in_size = p->next_packet_size;
> > +    uint32_t flags = p->flags & MULTIFD_FLAG_COMPRESSION_MASK;
> > +    uint32_t hdr_len = p->normal_num * sizeof(uint32_t);
> > +    uint32_t data_len = 0;
> > +    uint8_t *buf = uadk_data->buf;
> > +    int ret = 0;
> > +
> > +    if (flags != MULTIFD_FLAG_UADK) {
> > +        error_setg(errp, "multifd %u: flags received %x flags expected %x",
> > +                   p->id, flags, MULTIFD_FLAG_ZLIB);
> > +        return -1;
> > +    }
> > +
> > +    multifd_recv_zero_page_process(p);
> > +    if (!p->normal_num) {
> > +        assert(in_size == 0);
> > +        return 0;
> > +    }
> > +
> > +    /* read compressed data lengths */
> > +    assert(hdr_len < in_size);
> > +    ret = qio_channel_read_all(p->c, (void *) uadk_data->buf_hdr,
> > +                               hdr_len, errp);
> > +    if (ret != 0) {
> > +        return ret;
> > +    }
> > +
> > +    for (int i = 0; i < p->normal_num; i++) {
> > +        uadk_data->buf_hdr[i] = be32_to_cpu(uadk_data->buf_hdr[i]);
> > +        data_len += uadk_data->buf_hdr[i];
> > +        assert(uadk_data->buf_hdr[i] <= p->page_size);
> > +    }
> > +
> > +    /* read compressed data */
> > +    assert(in_size == hdr_len + data_len);
> > +    ret = qio_channel_read_all(p->c, (void *)buf, data_len, errp);
> > +    if (ret != 0) {
> > +        return ret;
> > +    }
> > +
> > +    for (int i = 0; i < p->normal_num; i++) {
> > +        struct wd_comp_req creq = {
> > +            .op_type = WD_DIR_DECOMPRESS,
> > +            .src     = buf,
> > +            .src_len = uadk_data->buf_hdr[i],
> > +            .dst     = p->host + p->normal[i],
> > +            .dst_len = p->page_size,
> > +        };
> > +
> > +        if (uadk_data->buf_hdr[i] == p->page_size) {
> > +            memcpy(p->host + p->normal[i], buf, p->page_size);
> > +            buf += p->page_size;
> > +            continue;
> > +        }
> > +
> > +        ret = wd_do_comp_sync(uadk_data->handle, &creq);
> > +        if (ret || creq.status) {
> > +            error_setg(errp, "multifd %u: failed wd_do_comp_sync, ret %d
> status %d",
> > +                       p->id, ret, creq.status);
> 
> It would be nice to be able to tell compression from decompression in
> these error messages.

Ok. Will change.

Thanks,
Shameer