[Xen-devel] [PATCH 5 of 5] Allocate non-contiguous per-cpu trace buffers

[Olaf Hering <olaf@xxxxxxxxx>]

# HG changeset patch
# User Olaf Hering <olaf@xxxxxxxxx>
# Date 1304706230 -7200
# Node ID bcd0b17bf8a3ab08760b8dcc1ca276defab1ed71
# Parent  1c5da4d9e33c821b9e3276d7aefe7ee16ce7b162
Allocate non-contiguous per-cpu trace buffers.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

diff -r 1c5da4d9e33c -r bcd0b17bf8a3 xen/common/trace.c
--- a/xen/common/trace.c        Fri May 06 18:54:41 2011 +0200
+++ b/xen/common/trace.c        Fri May 06 20:23:50 2011 +0200
@@ -151,7 +151,7 @@ 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;
     uint32_t t_info_first_offset;
@@ -167,32 +167,10 @@ 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;
-
-    /*
-     * 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;
-    }
+        goto out_dealloc_t_info;
 
     offset = t_info_first_offset;
     t_info_mfn_list = (uint32_t *)t_info;
@@ -204,27 +182,50 @@ 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);
-
-        for ( i = 0; i < pages; i++ )
-        {
-            share_xen_page_with_privileged_guests(p + i, XENSHARE_writable);
-
-            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;
+        void *p;
+        struct t_buf *buf;
+        struct page_info *pg;
 
         spin_lock_init(&per_cpu(t_lock, cpu));
+        /* first allocate the first page, it contains the per-cpu metadata */
+        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, 0);
+            goto out_dealloc;
+        }
+        per_cpu(t_bufs, cpu) = buf = p;
+        buf->cons = buf->prod = 0;
+
+        t_info->mfn_offset[cpu] = offset;
+        t_info_mfn_list[offset] = virt_to_mfn(p);
+        pg = virt_to_page(p);
+        share_xen_page_with_privileged_guests(pg, XENSHARE_writable);
+
+        printk(XENLOG_INFO "xentrace: p%d mfn %lx offset %d\n",
+               cpu, virt_to_mfn(p), offset);
+
+        /* now the remaining trace pages */
+        offset++;
+        for ( i = 1; i < pages; i++ )
+        {
+            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);
+                goto out_dealloc;
+            }
+            t_info_mfn_list[offset++] = virt_to_mfn(p);
+            pg = virt_to_page(p);
+            share_xen_page_with_privileged_guests(pg, XENSHARE_writable);
+        }
     }
 
     data_size  = (pages * PAGE_SIZE - sizeof(struct t_buf));
@@ -240,14 +241,18 @@ 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];
+        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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