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;
