Re: [Xen-devel] [PATCH 4 of 4] xentrace: allocate non-contiguous per-cpu trace buffers

[George Dunlap <dunlapg@xxxxxxxxx>]

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

On Tue, May 10, 2011 at 3:32 PM, Olaf Hering <olaf@xxxxxxxxx> wrote:
> # HG changeset patch
> # User Olaf Hering <olaf@xxxxxxxxx>
> # Date 1305037567 -7200
> # Node ID 7f6a118d237e60ca6f30723db687b06a8ef3c3e9
> # Parent  1a45e40add8b407532374c34f20bad51707808cf
> xentrace: allocate non-contiguous per-cpu trace buffers
>
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
>
> diff -r 1a45e40add8b -r 7f6a118d237e xen/common/trace.c
> --- a/xen/common/trace.c        Tue May 10 16:25:39 2011 +0200
> +++ b/xen/common/trace.c        Tue May 10 16:26:07 2011 +0200
> @@ -166,7 +166,7 @@ static int calculate_tbuf_size(unsigned
>  */
>  static int alloc_trace_bufs(unsigned int pages)
>  {
> -    int i, cpu, order;
> +    int i, cpu;
>     /* Start after a fixed-size array of NR_CPUS */
>     uint32_t *t_info_mfn_list;
>     uint16_t t_info_first_offset;
> @@ -182,34 +182,11 @@ static int alloc_trace_bufs(unsigned int
>     t_info_first_offset = calc_tinfo_first_offset();
>
>     pages = calculate_tbuf_size(pages, t_info_first_offset);
> -    order = get_order_from_pages(pages);
>
>     t_info = alloc_xenheap_pages(get_order_from_pages(t_info_pages), 0);
>     if ( t_info == NULL )
> -        goto out_dealloc;
> +        goto out_dealloc_t_info;
>
> -    /*
> -     * First, allocate buffers for all of the cpus.  If any
> -     * fails, deallocate what you have so far and exit.
> -     */
> -    for_each_online_cpu(cpu)
> -    {
> -        void *rawbuf;
> -        struct t_buf *buf;
> -
> -        if ( (rawbuf = alloc_xenheap_pages(
> -                order, MEMF_bits(32 + PAGE_SHIFT))) == NULL )
> -        {
> -            printk(XENLOG_INFO "xentrace: memory allocation failed "
> -                   "on cpu %d\n", cpu);
> -            goto out_dealloc;
> -        }
> -
> -        per_cpu(t_bufs, cpu) = buf = rawbuf;
> -        buf->cons = buf->prod = 0;
> -    }
> -
> -    offset = t_info_first_offset;
>     t_info_mfn_list = (uint32_t *)t_info;
>
>     for(i = 0; i < t_info_pages; i++)
> @@ -219,27 +196,53 @@ static int alloc_trace_bufs(unsigned int
>     t_info->tbuf_size = pages;
>
>     /*
> -     * Now share the pages so xentrace can map them, and write them in
> -     * the global t_info structure.
> +     * Allocate buffers for all of the cpus.
> +     * If any fails, deallocate what you have so far and exit.
>      */
>     for_each_online_cpu(cpu)
>     {
> -        void *rawbuf = per_cpu(t_bufs, cpu);
> -        struct page_info *p = virt_to_page(rawbuf);
> -        uint32_t mfn = virt_to_mfn(rawbuf);
> +        offset = t_info_first_offset + (cpu * pages);
> +        t_info->mfn_offset[cpu] = offset;
>
>         for ( i = 0; i < pages; i++ )
>         {
> -            share_xen_page_with_privileged_guests(p + i, XENSHARE_writable);
> +            void *p = alloc_xenheap_pages(0, MEMF_bits(32 + PAGE_SHIFT));
> +            if ( !p )
> +            {
> +                printk(XENLOG_INFO "xentrace: memory allocation failed "
> +                       "on cpu %d after %d pages\n", cpu, i);
> +                t_info_mfn_list[offset + i] = 0;
> +                goto out_dealloc;
> +            }
> +            t_info_mfn_list[offset + i] = virt_to_mfn(p);
> +        }
> +    }
>
> -            t_info_mfn_list[offset + i]=mfn + i;
> -        }
> -        t_info->mfn_offset[cpu]=offset;
> -        printk(XENLOG_INFO "xentrace: p%d mfn %"PRIx32" offset %d\n",
> -               cpu, mfn, offset);
> -        offset+=i;
> +    /*
> +     * Initialize buffers for all of the cpus.
> +     */
> +    for_each_online_cpu(cpu)
> +    {
> +        struct t_buf *buf;
> +        struct page_info *pg;
>
>         spin_lock_init(&per_cpu(t_lock, cpu));
> +
> +        offset = t_info->mfn_offset[cpu];
> +
> +        /* Initialize the buffer metadata */
> +        per_cpu(t_bufs, cpu) = buf = mfn_to_virt(t_info_mfn_list[offset]);
> +        buf->cons = buf->prod = 0;
> +
> +        printk(XENLOG_INFO "xentrace: p%d mfn %x offset %u\n",
> +                   cpu, t_info_mfn_list[offset], offset);
> +
> +        /* Now share the trace pages */
> +        for ( i = 0; i < pages; i++ )
> +        {
> +            pg = mfn_to_page(t_info_mfn_list[offset + i]);
> +            share_xen_page_with_privileged_guests(pg, XENSHARE_writable);
> +        }
>     }
>
>     data_size  = (pages * PAGE_SIZE - sizeof(struct t_buf));
> @@ -255,14 +258,19 @@ static int alloc_trace_bufs(unsigned int
>  out_dealloc:
>     for_each_online_cpu(cpu)
>     {
> -        void *rawbuf = per_cpu(t_bufs, cpu);
> -        per_cpu(t_bufs, cpu) = NULL;
> -        if ( rawbuf )
> +        offset = t_info->mfn_offset[cpu];
> +        if ( !offset )
> +            continue;
> +        for ( i = 0; i < pages; i++ )
>         {
> -            ASSERT(!(virt_to_page(rawbuf)->count_info & PGC_allocated));
> -            free_xenheap_pages(rawbuf, order);
> +            uint32_t mfn = t_info_mfn_list[offset + i];
> +            if ( !mfn )
> +                break;
> +            ASSERT(!(mfn_to_page(mfn)->count_info & PGC_allocated));
> +            free_xenheap_pages(mfn_to_virt(mfn), 0);
>         }
>     }
> +out_dealloc_t_info:
>     free_xenheap_pages(t_info, get_order_from_pages(t_info_pages));
>     t_info = NULL;
>     printk(XENLOG_WARNING "xentrace: allocation failed! Tracing disabled.\n");
>
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>

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