Re: [Xen-devel] [PATCH 4 of 5 V2] tools/libxl: Control network buffering in remus callbacks

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-08-29 at 15:16 -0700, Shriram Rajagopalan wrote:
> # HG changeset patch
> # User Shriram Rajagopalan <rshriram@xxxxxxxxx>
> # Date 1377813001 25200
> # Node ID b8839e0b61c2e15b94a274cfddedf0814d2560de
> # Parent  3e8b0aa7cd4a945ec3efe14c969700c9e23ea2cc
> tools/libxl: Control network buffering in remus callbacks
> 
> This patch constitutes the core network buffering logic.
> and does the following:
>  a) create a new network buffer when the domain is suspended
>     (remus_domain_suspend_callback)
>  b) release the previous network buffer pertaining to the
>     committed checkpoint (remus_domain_checkpoint_dm_saved)
> 
> Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx>

Looks ok to me, but I'd like Ian's opinion on the interactions with the
async stuff in the previous patch.

> 
> diff -r 3e8b0aa7cd4a -r b8839e0b61c2 tools/libxl/libxl_dom.c
> --- a/tools/libxl/libxl_dom.c Thu Aug 29 14:36:36 2013 -0700
> +++ b/tools/libxl/libxl_dom.c Thu Aug 29 14:50:01 2013 -0700
> @@ -1215,8 +1215,24 @@ int libxl__toolstack_save(uint32_t domid
>  
>  static int libxl__remus_domain_suspend_callback(void *data)
>  {
> -    /* REMUS TODO: Issue disk and network checkpoint reqs. */
> -    return libxl__domain_suspend_common_callback(data);
> +    /* REMUS TODO: Issue disk checkpoint reqs. */
> +    libxl__save_helper_state *shs = data;
> +    libxl__domain_suspend_state *dss = CONTAINER_OF(shs, *dss, shs);
> +    libxl__remus_ctx *remus_ctx = dss->remus_ctx;
> +    bool is_suspended;
> +    STATE_AO_GC(dss->ao);
> +
> +    is_suspended = !!libxl__domain_suspend_common_callback(data);
> +
> +    if (!remus_ctx->netbuf_ctx) return is_suspended;
> +
> +    if (is_suspended) {
> +        if (libxl__remus_netbuf_start_new_epoch(gc, dss->domid,
> +                                                remus_ctx))
> +            return !is_suspended;
> +    }
> +
> +    return is_suspended;
>  }
>  
>  static int libxl__remus_domain_resume_callback(void *data)
> @@ -1229,7 +1245,7 @@ static int libxl__remus_domain_resume_ca
>      if (libxl__domain_resume(gc, dss->domid, /* Fast Suspend */1))
>          return 0;
>  
> -    /* REMUS TODO: Deal with disk. Start a new network output buffer */
> +    /* REMUS TODO: Deal with disk. */
>      return 1;
>  }
>  
> @@ -1256,10 +1272,36 @@ static void libxl__remus_domain_checkpoi
>  static void remus_checkpoint_dm_saved(libxl__egc *egc,
>                                        libxl__domain_suspend_state *dss, int 
> rc)
>  {
> -    /* REMUS TODO: Wait for disk and memory ack, release network buffer */
> -    /* REMUS TODO: make this asynchronous */
> -    assert(!rc); /* REMUS TODO handle this error properly */
> -    usleep(dss->remus_ctx->interval * 1000);
> +    /*
> +     * REMUS TODO: Wait for disk and explicit memory ack (through restore
> +     * callback from remote) before releasing network buffer.
> +     */
> +    libxl__remus_ctx *remus_ctx = dss->remus_ctx;
> +    struct timespec epoch;
> +    int ret;
> +    STATE_AO_GC(dss->ao);
> +
> +    if (rc) {
> +        LOG(ERROR, "Failed to save device model. Terminating Remus..");
> +        libxl__xc_domain_saverestore_async_callback_done(egc,
> +                                                         &dss->shs, rc);
> +        return;
> +    }
> +
> +    if (remus_ctx->netbuf_ctx) {
> +        ret = libxl__remus_netbuf_release_prev_epoch(gc, dss->domid,
> +                                                     remus_ctx);
> +        if (ret) {
> +            libxl__xc_domain_saverestore_async_callback_done(egc,
> +                                                             &dss->shs,
> +                                                             ret);
> +            return;
> +        }
> +    }
> +
> +    epoch.tv_sec = remus_ctx->interval / 1000; /* interval is in ms */
> +    epoch.tv_nsec = remus_ctx->interval * 1000L * 1000L;
> +    nanosleep(&epoch, 0);
>      libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, 1);
>  }
>  



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