[PATCH 4/4] tools/libs/guest: allocate various migration arrays just once

[Frediano Ziglio <freddy77@xxxxxxxxx>]

From: Edwin Török <edwin.torok@xxxxxxxxxx>

Allocate these array just once at the start of migration,
using the maximum batch size, and free them at the end.

Signed-off-by: Edwin Török <edwin.torok@xxxxxxxxxx>
Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
---
 tools/libs/guest/xg_sr_common.h | 13 +++++++
 tools/libs/guest/xg_sr_save.c   | 66 +++++++++++++--------------------
 2 files changed, 39 insertions(+), 40 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index f1573aefcb..77312bae9c 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -209,6 +209,18 @@ static inline int update_blob(struct xc_sr_blob *blob,
     return 0;
 }
 
+struct xc_sr_context_save_buffers
+{
+    xen_pfn_t batch_pfns[MAX_BATCH_SIZE];
+    xen_pfn_t mfns[MAX_BATCH_SIZE];
+    xen_pfn_t types[MAX_BATCH_SIZE];
+    int errors[MAX_BATCH_SIZE];
+    void *guest_data[MAX_BATCH_SIZE];
+    void *local_pages[MAX_BATCH_SIZE];
+    struct iovec iov[MAX_BATCH_SIZE + 2]; /* headers + data */
+    uint64_t rec_pfns[MAX_BATCH_SIZE];
+};
+
 struct xc_sr_context
 {
     xc_interface *xch;
@@ -244,6 +256,7 @@ struct xc_sr_context
             unsigned long *deferred_pages;
             unsigned long nr_deferred_pages;
             xc_hypercall_buffer_t dirty_bitmap_hbuf;
+            struct xc_sr_context_save_buffers *buffers;
         } save;
 
         struct /* Restore data. */
diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 1700d81905..64014dcdbd 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -87,16 +87,16 @@ static int write_checkpoint_record(struct xc_sr_context 
*ctx)
 static int write_batch(struct xc_sr_context *ctx)
 {
     xc_interface *xch = ctx->xch;
-    xen_pfn_t *mfns = NULL, *types = NULL;
+    xen_pfn_t *mfns, *types;
     void *guest_mapping = NULL;
-    void **guest_data = NULL;
-    void **local_pages = NULL;
-    int *errors = NULL, rc = -1;
+    void **guest_data;
+    void **local_pages;
+    int *errors, rc = -1;
     unsigned int i, p, nr_pages = 0, nr_pages_mapped = 0;
     unsigned int nr_pfns = ctx->save.nr_batch_pfns;
     void *page, *orig_page;
-    uint64_t *rec_pfns = NULL;
-    struct iovec *iov = NULL; int iovcnt = 0;
+    uint64_t *rec_pfns;
+    struct iovec *iov; int iovcnt = 0;
     struct {
         struct xc_sr_rhdr rec;
         struct xc_sr_rec_page_data_header page_data;
@@ -106,26 +106,24 @@ static int write_batch(struct xc_sr_context *ctx)
     };
 
     assert(nr_pfns != 0);
+    assert(nr_pfns <= MAX_BATCH_SIZE);
+    assert(ctx->save.buffers);
 
     /* Mfns of the batch pfns. */
-    mfns = malloc(nr_pfns * sizeof(*mfns));
+    mfns = ctx->save.buffers->mfns;
     /* Types of the batch pfns. */
-    types = malloc(nr_pfns * sizeof(*types));
+    types = ctx->save.buffers->types;
     /* Errors from attempting to map the gfns. */
-    errors = malloc(nr_pfns * sizeof(*errors));
+    errors = ctx->save.buffers->errors;
     /* Pointers to page data to send.  Mapped gfns or local allocations. */
-    guest_data = calloc(nr_pfns, sizeof(*guest_data));
+    guest_data = ctx->save.buffers->guest_data;
+    memset(guest_data, 0, sizeof(*guest_data) * nr_pfns);
     /* Pointers to locally allocated pages.  Need freeing. */
-    local_pages = calloc(nr_pfns, sizeof(*local_pages));
+    local_pages = ctx->save.buffers->local_pages;
+    memset(local_pages, 0, sizeof(*local_pages) * nr_pfns);
     /* iovec[] for writev(). */
-    iov = malloc((nr_pfns + 2) * sizeof(*iov));
-
-    if ( !mfns || !types || !errors || !guest_data || !local_pages || !iov )
-    {
-        ERROR("Unable to allocate arrays for a batch of %u pages",
-              nr_pfns);
-        goto err;
-    }
+    iov = ctx->save.buffers->iov;
+    rec_pfns = ctx->save.buffers->rec_pfns;
 
     for ( i = 0; i < nr_pfns; ++i )
     {
@@ -211,14 +209,6 @@ static int write_batch(struct xc_sr_context *ctx)
         }
     }
 
-    rec_pfns = malloc(nr_pfns * sizeof(*rec_pfns));
-    if ( !rec_pfns )
-    {
-        ERROR("Unable to allocate %zu bytes of memory for page data pfn list",
-              nr_pfns * sizeof(*rec_pfns));
-        goto err;
-    }
-
     hdrs.rec.length = sizeof(hdrs.page_data);
     hdrs.rec.length += nr_pfns * sizeof(*rec_pfns);
     hdrs.rec.length += nr_pages * PAGE_SIZE;
@@ -261,17 +251,13 @@ static int write_batch(struct xc_sr_context *ctx)
     rc = ctx->save.nr_batch_pfns = 0;
 
  err:
-    free(rec_pfns);
     if ( guest_mapping )
         xenforeignmemory_unmap(xch->fmem, guest_mapping, nr_pages_mapped);
     for ( i = 0; local_pages && i < nr_pfns; ++i )
+    {
         free(local_pages[i]);
-    free(iov);
-    free(local_pages);
-    free(guest_data);
-    free(errors);
-    free(types);
-    free(mfns);
+        local_pages[i] = NULL;
+    }
 
     return rc;
 }
@@ -799,18 +785,18 @@ static int setup(struct xc_sr_context *ctx)
 
     dirty_bitmap = xc_hypercall_buffer_alloc_pages(
         xch, dirty_bitmap, NRPAGES(bitmap_size(ctx->save.p2m_size)));
-    ctx->save.batch_pfns = malloc(MAX_BATCH_SIZE *
-                                  sizeof(*ctx->save.batch_pfns));
     ctx->save.deferred_pages = bitmap_alloc(ctx->save.p2m_size);
+    ctx->save.buffers = calloc(1, sizeof(*ctx->save.buffers));
 
-    if ( !ctx->save.batch_pfns || !dirty_bitmap || !ctx->save.deferred_pages )
+    if ( !dirty_bitmap || !ctx->save.deferred_pages || !ctx->save.buffers)
     {
-        ERROR("Unable to allocate memory for dirty bitmaps, batch pfns and"
-              " deferred pages");
+        ERROR("Unable to allocate memory for dirty bitmaps, deferred pages"
+              " and various batch buffers");
         rc = -1;
         errno = ENOMEM;
         goto err;
     }
+    ctx->save.batch_pfns = ctx->save.buffers->batch_pfns;
 
     rc = 0;
 
@@ -834,7 +820,7 @@ static void cleanup(struct xc_sr_context *ctx)
     xc_hypercall_buffer_free_pages(xch, dirty_bitmap,
                                    NRPAGES(bitmap_size(ctx->save.p2m_size)));
     free(ctx->save.deferred_pages);
-    free(ctx->save.batch_pfns);
+    free(ctx->save.buffers);
 }
 
 /*
-- 
2.43.0