File xen.sr-save-iov.patch of Package xen

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File xen.sr-save-iov.patch of Package xen

From: Olaf Hering <olaf@aepfle.de>
Date: Fri, 23 Oct 2020 11:30:41 +0200
Subject: sr save iov

tools: save: preallocate iov array

Remove repeated allocation from migration loop. There will never be
more than MAX_BATCH_SIZE pages to process in a batch.
Allocate the space once.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 tools/libs/guest/xg_sr_common.h |  1 +
 tools/libs/guest/xg_sr_save.c   | 34 ++++-----
 2 files changed, 18 insertions(+), 17 deletions(-)

--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -238,24 +238,25 @@ struct xc_sr_context
             bool debug;
 
             unsigned long p2m_size;
             size_t pages_sent;
             size_t overhead_sent;
 
             struct precopy_stats stats;
 
             xen_pfn_t *batch_pfns;
             xen_pfn_t *mfns;
             xen_pfn_t *types;
             int *errors;
+            struct iovec *iov;
             unsigned int nr_batch_pfns;
             unsigned long *deferred_pages;
             unsigned long nr_deferred_pages;
             xc_hypercall_buffer_t dirty_bitmap_hbuf;
         } save;
 
         struct /* Restore data. */
         {
             struct xc_sr_restore_ops ops;
             struct restore_callbacks *callbacks;
 
             int send_back_fd;
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -87,40 +87,38 @@ static int write_checkpoint_record(struct xc_sr_context *ctx)
  */
 static int write_batch(struct xc_sr_context *ctx)
 {
     xc_interface *xch = ctx->xch;
     void *guest_mapping = NULL;
     void **guest_data = NULL;
     void **local_pages = NULL;
     int 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;
+    int iovcnt = 0;
     struct xc_sr_rec_page_data_header hdr = { 0 };
     struct xc_sr_record rec = {
         .type = REC_TYPE_PAGE_DATA,
     };
 
     assert(nr_pfns != 0);
 
     /* Pointers to page data to send.  Mapped gfns or local allocations. */
     guest_data = calloc(nr_pfns, sizeof(*guest_data));
     /* Pointers to locally allocated pages.  Need freeing. */
     local_pages = calloc(nr_pfns, sizeof(*local_pages));
-    /* iovec[] for writev(). */
-    iov = malloc((nr_pfns + 4) * sizeof(*iov));
 
-    if ( !guest_data || !local_pages || !iov )
+    if ( !guest_data || !local_pages )
     {
         ERROR("Unable to allocate arrays for a batch of %u pages",
               nr_pfns);
         goto err;
     }
 
     for ( i = 0; i < nr_pfns; ++i )
     {
         ctx->save.types[i] = ctx->save.mfns[i] = ctx->save.ops.pfn_to_gfn(ctx,
                                                       ctx->save.batch_pfns[i]);
 
         /* Likely a ballooned page. */
@@ -212,71 +210,70 @@ static int write_batch(struct xc_sr_context *ctx)
         goto err;
     }
 
     hdr.count = nr_pfns;
 
     rec.length = sizeof(hdr);
     rec.length += nr_pfns * sizeof(*rec_pfns);
     rec.length += nr_pages * PAGE_SIZE;
 
     for ( i = 0; i < nr_pfns; ++i )
         rec_pfns[i] = ((uint64_t)(ctx->save.types[i]) << 32) | ctx->save.batch_pfns[i];
 
-    iov[0].iov_base = &rec.type;
-    iov[0].iov_len = sizeof(rec.type);
+    ctx->save.iov[0].iov_base = &rec.type;
+    ctx->save.iov[0].iov_len = sizeof(rec.type);
 
-    iov[1].iov_base = &rec.length;
-    iov[1].iov_len = sizeof(rec.length);
+    ctx->save.iov[1].iov_base = &rec.length;
+    ctx->save.iov[1].iov_len = sizeof(rec.length);
 
-    iov[2].iov_base = &hdr;
-    iov[2].iov_len = sizeof(hdr);
+    ctx->save.iov[2].iov_base = &hdr;
+    ctx->save.iov[2].iov_len = sizeof(hdr);
 
-    iov[3].iov_base = rec_pfns;
-    iov[3].iov_len = nr_pfns * sizeof(*rec_pfns);
+    ctx->save.iov[3].iov_base = rec_pfns;
+    ctx->save.iov[3].iov_len = nr_pfns * sizeof(*rec_pfns);
 
     iovcnt = 4;
     ctx->save.pages_sent += nr_pages;
     ctx->save.overhead_sent += sizeof(rec) + sizeof(hdr) + nr_pfns * sizeof(*rec_pfns);
 
     if ( nr_pages )
     {
         for ( i = 0; i < nr_pfns; ++i )
         {
             if ( guest_data[i] )
             {
-                iov[iovcnt].iov_base = guest_data[i];
-                iov[iovcnt].iov_len = PAGE_SIZE;
+                ctx->save.iov[iovcnt].iov_base = guest_data[i];
+                ctx->save.iov[iovcnt].iov_len = PAGE_SIZE;
                 iovcnt++;
                 --nr_pages;
             }
         }
     }
 
-    if ( writev_exact(ctx->fd, iov, iovcnt) )
+    if ( writev_exact(ctx->fd, ctx->save.iov, iovcnt) )
     {
         PERROR("Failed to write page data to stream");
         goto err;
     }
 
     /* Sanity check we have sent all the pages we expected to. */
     assert(nr_pages == 0);
     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);
 
     return rc;
 }
 
 /*
  * Flush a batch of pfns into the stream.
  */
 static int flush_batch(struct xc_sr_context *ctx)
 {
     int rc = 0;
@@ -836,28 +833,30 @@ static int setup(struct xc_sr_context *ctx)
 
     rc = ctx->save.ops.setup(ctx);
     if ( rc )
         goto err;
 
     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.mfns = malloc(MAX_BATCH_SIZE * sizeof(*ctx->save.mfns));
     ctx->save.types = malloc(MAX_BATCH_SIZE * sizeof(*ctx->save.types));
     ctx->save.errors = malloc(MAX_BATCH_SIZE * sizeof(*ctx->save.errors));
+    ctx->save.iov = malloc((4 + MAX_BATCH_SIZE) * sizeof(*ctx->save.iov));
     ctx->save.deferred_pages = bitmap_alloc(ctx->save.p2m_size);
 
     if ( !ctx->save.batch_pfns || !ctx->save.mfns || !ctx->save.types ||
-         !ctx->save.errors || !dirty_bitmap || !ctx->save.deferred_pages )
+         !ctx->save.errors || !ctx->save.iov || !dirty_bitmap ||
+         !ctx->save.deferred_pages )
     {
         ERROR("Unable to allocate memory for dirty bitmaps, batch pfns and"
               " deferred pages");
         rc = -1;
         errno = ENOMEM;
         goto err;
     }
 
     rc = 0;
 
  err:
     return rc;
@@ -870,24 +869,25 @@ static void cleanup(struct xc_sr_context *ctx)
                                     &ctx->save.dirty_bitmap_hbuf);
 
 
     xc_shadow_control(xch, ctx->domid, XEN_DOMCTL_SHADOW_OP_OFF,
                       NULL, 0);
 
     if ( ctx->save.ops.cleanup(ctx) )
         PERROR("Failed to clean up");
 
     xc_hypercall_buffer_free_pages(xch, dirty_bitmap,
                                    NRPAGES(bitmap_size(ctx->save.p2m_size)));
     free(ctx->save.deferred_pages);
+    free(ctx->save.iov);
     free(ctx->save.errors);
     free(ctx->save.types);
     free(ctx->save.mfns);
     free(ctx->save.batch_pfns);
 }
 
 /*
  * Save a domain.
  */
 static int save(struct xc_sr_context *ctx, uint16_t guest_type)
 {
     xc_interface *xch = ctx->xch;

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File xen.sr-save-iov.patch of Package xen

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