[PATCH v20210111 20/39] tools/guest: save: move rec_pfns array

[Olaf Hering <olaf@xxxxxxxxx>]

Remove allocation from hotpath, move rec_pfns array into preallocated space.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
 tools/libs/guest/xg_sr_common.h |  2 ++
 tools/libs/guest/xg_sr_save.c   | 11 +----------
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index f315b4f526..81158a4f4d 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -221,6 +221,8 @@ struct xc_sr_save_arrays {
     int errors[MAX_BATCH_SIZE];
     /* write_batch: iovec[] for writev(). */
     struct iovec iov[MAX_BATCH_SIZE + 4];
+    /* write_batch */
+    uint64_t rec_pfns[MAX_BATCH_SIZE];
 };
 
 struct xc_sr_restore_arrays {
diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 1d04bd0a44..0e34c4b051 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -96,7 +96,7 @@ static int write_batch(struct xc_sr_context *ctx)
     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;
+    uint64_t *rec_pfns = ctx->save.m->rec_pfns;
     struct iovec *iov = ctx->save.m->iov; int iovcnt = 0;
     struct xc_sr_rec_page_data_header hdr = { 0 };
     struct xc_sr_record rec = {
@@ -201,14 +201,6 @@ 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;
-    }
-
     hdr.count = nr_pfns;
 
     rec.length = sizeof(hdr);
@@ -259,7 +251,6 @@ 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 )