xen/privcmd: improve performance of MMAPBATCH_V2
Make the IOCTL_PRIVCMD_MMAPBATCH_V2 (and older V1 version) map
multiple frames at a time rather than one at a time, despite the pages
being non-consecutive GFNs.
xen_remap_foreign_mfn_array() is added which maps an array of GFNs
(instead of a consecutive range of GFNs).
Since per-frame errors are returned in an array, privcmd must set the
MMAPBATCH_V1 error bits as part of the "report errors" phase, after
all the frames are mapped.
Migrate times are significantly improved (when using a PV toolstack
domain). For example, for an idle 12 GiB PV guest:
Before After
real 0m38.179s 0m26.868s
user 0m15.096s 0m13.652s
sys 0m28.988s 0m18.732s
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 59ac71c..5a29616 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -159,6 +159,40 @@
return ret;
}
+/*
+ * Similar to traverse_pages, but use each page as a "block" of
+ * data to be processed as one unit.
+ */
+static int traverse_pages_block(unsigned nelem, size_t size,
+ struct list_head *pos,
+ int (*fn)(void *data, int nr, void *state),
+ void *state)
+{
+ void *pagedata;
+ unsigned pageidx;
+ int ret = 0;
+
+ BUG_ON(size > PAGE_SIZE);
+
+ pageidx = PAGE_SIZE;
+
+ while (nelem) {
+ int nr = (PAGE_SIZE/size);
+ struct page *page;
+ if (nr > nelem)
+ nr = nelem;
+ pos = pos->next;
+ page = list_entry(pos, struct page, lru);
+ pagedata = page_address(page);
+ ret = (*fn)(pagedata, nr, state);
+ if (ret)
+ break;
+ nelem -= nr;
+ }
+
+ return ret;
+}
+
struct mmap_mfn_state {
unsigned long va;
struct vm_area_struct *vma;
@@ -274,39 +308,25 @@
/* auto translated dom0 note: if domU being created is PV, then mfn is
* mfn(addr on bus). If it's auto xlated, then mfn is pfn (input to HAP).
*/
-static int mmap_batch_fn(void *data, void *state)
+static int mmap_batch_fn(void *data, int nr, void *state)
{
xen_pfn_t *mfnp = data;
struct mmap_batch_state *st = state;
struct vm_area_struct *vma = st->vma;
struct page **pages = vma->vm_private_data;
- struct page *cur_page = NULL;
+ struct page **cur_pages = NULL;
int ret;
if (xen_feature(XENFEAT_auto_translated_physmap))
- cur_page = pages[st->index++];
+ cur_pages = &pages[st->index];
- ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
- st->vma->vm_page_prot, st->domain,
- &cur_page);
+ BUG_ON(nr < 0);
+ ret = xen_remap_domain_mfn_array(st->vma, st->va & PAGE_MASK, mfnp, nr,
+ (int *)mfnp, st->vma->vm_page_prot,
+ st->domain, cur_pages);
- /* Store error code for second pass. */
- if (st->version == 1) {
- if (ret < 0) {
- /*
- * V1 encodes the error codes in the 32bit top nibble of the
- * mfn (with its known limitations vis-a-vis 64 bit callers).
- */
- *mfnp |= (ret == -ENOENT) ?
- PRIVCMD_MMAPBATCH_PAGED_ERROR :
- PRIVCMD_MMAPBATCH_MFN_ERROR;
- }
- } else { /* st->version == 2 */
- *((int *) mfnp) = ret;
- }
-
- /* And see if it affects the global_error. */
- if (ret < 0) {
+ /* Adjust the global_error? */
+ if (ret != nr) {
if (ret == -ENOENT)
st->global_error = -ENOENT;
else {
@@ -315,23 +335,35 @@
st->global_error = 1;
}
}
- st->va += PAGE_SIZE;
+ st->va += PAGE_SIZE * nr;
+ st->index += nr;
return 0;
}
-static int mmap_return_errors(void *data, void *state)
+static int mmap_return_error(int err, struct mmap_batch_state *st)
{
- struct mmap_batch_state *st = state;
+ int ret;
if (st->version == 1) {
- xen_pfn_t mfnp = *((xen_pfn_t *) data);
- if (mfnp & PRIVCMD_MMAPBATCH_MFN_ERROR)
- return __put_user(mfnp, st->user_mfn++);
- else
+ if (err) {
+ xen_pfn_t mfn;
+
+ ret = get_user(mfn, st->user_mfn);
+ if (ret < 0)
+ return ret;
+ /*
+ * V1 encodes the error codes in the 32bit top
+ * nibble of the mfn (with its known
+ * limitations vis-a-vis 64 bit callers).
+ */
+ mfn |= (err == -ENOENT) ?
+ PRIVCMD_MMAPBATCH_PAGED_ERROR :
+ PRIVCMD_MMAPBATCH_MFN_ERROR;
+ return __put_user(mfn, st->user_mfn++);
+ } else
st->user_mfn++;
} else { /* st->version == 2 */
- int err = *((int *) data);
if (err)
return __put_user(err, st->user_err++);
else
@@ -341,6 +373,21 @@
return 0;
}
+static int mmap_return_errors(void *data, int nr, void *state)
+{
+ struct mmap_batch_state *st = state;
+ int *errs = data;
+ int i;
+ int ret;
+
+ for (i = 0; i < nr; i++) {
+ ret = mmap_return_error(errs[i], st);
+ if (ret < 0)
+ return ret;
+ }
+ return 0;
+}
+
/* Allocate pfns that are then mapped with gmfns from foreign domid. Update
* the vma with the page info to use later.
* Returns: 0 if success, otherwise -errno
@@ -472,8 +519,8 @@
state.version = version;
/* mmap_batch_fn guarantees ret == 0 */
- BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
- &pagelist, mmap_batch_fn, &state));
+ BUG_ON(traverse_pages_block(m.num, sizeof(xen_pfn_t),
+ &pagelist, mmap_batch_fn, &state));
up_write(&mm->mmap_sem);
@@ -481,8 +528,8 @@
/* Write back errors in second pass. */
state.user_mfn = (xen_pfn_t *)m.arr;
state.user_err = m.err;
- ret = traverse_pages(m.num, sizeof(xen_pfn_t),
- &pagelist, mmap_return_errors, &state);
+ ret = traverse_pages_block(m.num, sizeof(xen_pfn_t),
+ &pagelist, mmap_return_errors, &state);
} else
ret = 0;