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authorStefano Stabellini <stefano.stabellini@xilinx.com>2020-05-21 22:32:42 +0300
committerDominique Martinet <dominique.martinet@cea.fr>2020-06-02 09:00:39 +0300
commit36f9967531da27ff8cc6f005d93760b578baffb9 (patch)
treed6ae408bc9f69adc7dec094400c4b60aebcac8ec
parent3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162 (diff)
downloadlinux-36f9967531da27ff8cc6f005d93760b578baffb9.tar.xz
9p/xen: increase XEN_9PFS_RING_ORDER
Increase XEN_9PFS_RING_ORDER to 9 for performance reason. Order 9 is the max allowed by the protocol. We can't assume that all backends will support order 9. The xenstore property max-ring-page-order specifies the max order supported by the backend. We'll use max-ring-page-order for the size of the ring. This means that the size of the ring is not static (XEN_FLEX_RING_SIZE(9)) anymore. Change XEN_9PFS_RING_SIZE to take an argument and base the calculation on the order chosen at setup time. Finally, modify p9_xen_trans.maxsize to be divided by 4 compared to the original value. We need to divide it by 2 because we have two rings coming off the same order allocation: the in and out rings. This was a mistake in the original code. Also divide it further by 2 because we don't want a single request/reply to fill up the entire ring. There can be multiple requests/replies outstanding at any given time and if we use the full ring with one, we risk forcing the backend to wait for the client to read back more replies before continuing, which is not performant. Link: http://lkml.kernel.org/r/20200521193242.15953-1-sstabellini@kernel.org Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com> Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
-rw-r--r--net/9p/trans_xen.c61
1 files changed, 34 insertions, 27 deletions
diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 3963eb11c3fb..3debad93be1a 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -43,8 +43,8 @@
#include <net/9p/transport.h>
#define XEN_9PFS_NUM_RINGS 2
-#define XEN_9PFS_RING_ORDER 6
-#define XEN_9PFS_RING_SIZE XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
+#define XEN_9PFS_RING_ORDER 9
+#define XEN_9PFS_RING_SIZE(ring) XEN_FLEX_RING_SIZE(ring->intf->ring_order)
struct xen_9pfs_header {
uint32_t size;
@@ -132,8 +132,8 @@ static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
prod = ring->intf->out_prod;
virt_mb();
- return XEN_9PFS_RING_SIZE -
- xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) >= size;
+ return XEN_9PFS_RING_SIZE(ring) -
+ xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
}
static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
@@ -167,17 +167,18 @@ again:
prod = ring->intf->out_prod;
virt_mb();
- if (XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
- XEN_9PFS_RING_SIZE) < size) {
+ if (XEN_9PFS_RING_SIZE(ring) -
+ xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
spin_unlock_irqrestore(&ring->lock, flags);
goto again;
}
- masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
- masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
+ masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
+ masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
- &masked_prod, masked_cons, XEN_9PFS_RING_SIZE);
+ &masked_prod, masked_cons,
+ XEN_9PFS_RING_SIZE(ring));
p9_req->status = REQ_STATUS_SENT;
virt_wmb(); /* write ring before updating pointer */
@@ -207,19 +208,19 @@ static void p9_xen_response(struct work_struct *work)
prod = ring->intf->in_prod;
virt_rmb();
- if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) <
+ if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
sizeof(h)) {
notify_remote_via_irq(ring->irq);
return;
}
- masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
- masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
+ masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
+ masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
/* First, read just the header */
xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
masked_prod, &masked_cons,
- XEN_9PFS_RING_SIZE);
+ XEN_9PFS_RING_SIZE(ring));
req = p9_tag_lookup(priv->client, h.tag);
if (!req || req->status != REQ_STATUS_SENT) {
@@ -233,11 +234,11 @@ static void p9_xen_response(struct work_struct *work)
memcpy(&req->rc, &h, sizeof(h));
req->rc.offset = 0;
- masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
+ masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
/* Then, read the whole packet (including the header) */
xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
masked_prod, &masked_cons,
- XEN_9PFS_RING_SIZE);
+ XEN_9PFS_RING_SIZE(ring));
virt_mb();
cons += h.size;
@@ -267,7 +268,7 @@ static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
static struct p9_trans_module p9_xen_trans = {
.name = "xen",
- .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT),
+ .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
.def = 1,
.create = p9_xen_create,
.close = p9_xen_close,
@@ -295,14 +296,16 @@ static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
if (priv->rings[i].irq > 0)
unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
if (priv->rings[i].data.in) {
- for (j = 0; j < (1 << XEN_9PFS_RING_ORDER); j++) {
+ for (j = 0;
+ j < (1 << priv->rings[i].intf->ring_order);
+ j++) {
grant_ref_t ref;
ref = priv->rings[i].intf->ref[j];
gnttab_end_foreign_access(ref, 0, 0);
}
free_pages((unsigned long)priv->rings[i].data.in,
- XEN_9PFS_RING_ORDER -
+ priv->rings[i].intf->ring_order -
(PAGE_SHIFT - XEN_PAGE_SHIFT));
}
gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
@@ -323,7 +326,8 @@ static int xen_9pfs_front_remove(struct xenbus_device *dev)
}
static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
- struct xen_9pfs_dataring *ring)
+ struct xen_9pfs_dataring *ring,
+ unsigned int order)
{
int i = 0;
int ret = -ENOMEM;
@@ -342,21 +346,21 @@ static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
goto out;
ring->ref = ret;
bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
- XEN_9PFS_RING_ORDER - (PAGE_SHIFT - XEN_PAGE_SHIFT));
+ order - (PAGE_SHIFT - XEN_PAGE_SHIFT));
if (!bytes) {
ret = -ENOMEM;
goto out;
}
- for (; i < (1 << XEN_9PFS_RING_ORDER); i++) {
+ for (; i < (1 << order); i++) {
ret = gnttab_grant_foreign_access(
dev->otherend_id, virt_to_gfn(bytes) + i, 0);
if (ret < 0)
goto out;
ring->intf->ref[i] = ret;
}
- ring->intf->ring_order = XEN_9PFS_RING_ORDER;
+ ring->intf->ring_order = order;
ring->data.in = bytes;
- ring->data.out = bytes + XEN_9PFS_RING_SIZE;
+ ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
if (ret)
@@ -374,7 +378,7 @@ out:
for (i--; i >= 0; i--)
gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
free_pages((unsigned long)bytes,
- XEN_9PFS_RING_ORDER -
+ ring->intf->ring_order -
(PAGE_SHIFT - XEN_PAGE_SHIFT));
}
gnttab_end_foreign_access(ring->ref, 0, 0);
@@ -404,8 +408,10 @@ static int xen_9pfs_front_probe(struct xenbus_device *dev,
return -EINVAL;
max_ring_order = xenbus_read_unsigned(dev->otherend,
"max-ring-page-order", 0);
- if (max_ring_order < XEN_9PFS_RING_ORDER)
- return -EINVAL;
+ if (max_ring_order > XEN_9PFS_RING_ORDER)
+ max_ring_order = XEN_9PFS_RING_ORDER;
+ if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
+ p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
@@ -422,7 +428,8 @@ static int xen_9pfs_front_probe(struct xenbus_device *dev,
for (i = 0; i < priv->num_rings; i++) {
priv->rings[i].priv = priv;
- ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
+ ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
+ max_ring_order);
if (ret < 0)
goto error;
}