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authorChuck Lever <chuck.lever@oracle.com>2019-02-11 19:24:16 +0300
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2019-02-13 19:42:17 +0300
commit7be9cea3600ba24f45733f823cb4ecb5a40f5db7 (patch)
tree9c6fadf1ca63c7f2afd56293094f8484c641586d /net/sunrpc/xdr.c
parent5582863f450ca44c472dbf4812a62f4e0e68b0c8 (diff)
downloadlinux-7be9cea3600ba24f45733f823cb4ecb5a40f5db7.tar.xz
SUNRPC: Add trace event that reports reply page vector alignment
We don't want READ payloads that are partially in the head iovec and in the page buffer because this requires pull-up, which can be expensive. The NFS/RPC client tries hard to predict the size of the head iovec so that the incoming READ data payload lands only in the page vector, but it doesn't always get it right. To help diagnose such problems, add a trace point in the logic that decodes READ-like operations that reports whether pull-up is being done. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net/sunrpc/xdr.c')
-rw-r--r--net/sunrpc/xdr.c33
1 files changed, 27 insertions, 6 deletions
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 6d0b615a02ae..5f0aa53fa4ae 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -347,13 +347,15 @@ EXPORT_SYMBOL_GPL(_copy_from_pages);
* 'len' bytes. The extra data is not lost, but is instead
* moved into the inlined pages and/or the tail.
*/
-static void
+static unsigned int
xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
{
struct kvec *head, *tail;
size_t copy, offs;
unsigned int pglen = buf->page_len;
+ unsigned int result;
+ result = 0;
tail = buf->tail;
head = buf->head;
@@ -367,6 +369,7 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
copy = tail->iov_len - len;
memmove((char *)tail->iov_base + len,
tail->iov_base, copy);
+ result += copy;
}
/* Copy from the inlined pages into the tail */
copy = len;
@@ -377,11 +380,13 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
copy = 0;
else if (copy > tail->iov_len - offs)
copy = tail->iov_len - offs;
- if (copy != 0)
+ if (copy != 0) {
_copy_from_pages((char *)tail->iov_base + offs,
buf->pages,
buf->page_base + pglen + offs - len,
copy);
+ result += copy;
+ }
/* Do we also need to copy data from the head into the tail ? */
if (len > pglen) {
offs = copy = len - pglen;
@@ -391,6 +396,7 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
(char *)head->iov_base +
head->iov_len - offs,
copy);
+ result += copy;
}
}
/* Now handle pages */
@@ -406,12 +412,15 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
_copy_to_pages(buf->pages, buf->page_base,
(char *)head->iov_base + head->iov_len - len,
copy);
+ result += copy;
}
head->iov_len -= len;
buf->buflen -= len;
/* Have we truncated the message? */
if (buf->len > buf->buflen)
buf->len = buf->buflen;
+
+ return result;
}
/**
@@ -423,14 +432,16 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
* 'len' bytes. The extra data is not lost, but is instead
* moved into the tail.
*/
-static void
+static unsigned int
xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
{
struct kvec *tail;
size_t copy;
unsigned int pglen = buf->page_len;
unsigned int tailbuf_len;
+ unsigned int result;
+ result = 0;
tail = buf->tail;
BUG_ON (len > pglen);
@@ -448,18 +459,22 @@ xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
if (tail->iov_len > len) {
char *p = (char *)tail->iov_base + len;
memmove(p, tail->iov_base, tail->iov_len - len);
+ result += tail->iov_len - len;
} else
copy = tail->iov_len;
/* Copy from the inlined pages into the tail */
_copy_from_pages((char *)tail->iov_base,
buf->pages, buf->page_base + pglen - len,
copy);
+ result += copy;
}
buf->page_len -= len;
buf->buflen -= len;
/* Have we truncated the message? */
if (buf->len > buf->buflen)
buf->len = buf->buflen;
+
+ return result;
}
void
@@ -959,13 +974,17 @@ static unsigned int xdr_align_pages(struct xdr_stream *xdr, unsigned int len)
struct kvec *iov;
unsigned int nwords = XDR_QUADLEN(len);
unsigned int cur = xdr_stream_pos(xdr);
+ unsigned int copied, offset;
if (xdr->nwords == 0)
return 0;
+
/* Realign pages to current pointer position */
- iov = buf->head;
+ iov = buf->head;
if (iov->iov_len > cur) {
- xdr_shrink_bufhead(buf, iov->iov_len - cur);
+ offset = iov->iov_len - cur;
+ copied = xdr_shrink_bufhead(buf, offset);
+ trace_rpc_xdr_alignment(xdr, offset, copied);
xdr->nwords = XDR_QUADLEN(buf->len - cur);
}
@@ -977,7 +996,9 @@ static unsigned int xdr_align_pages(struct xdr_stream *xdr, unsigned int len)
len = buf->page_len;
else if (nwords < xdr->nwords) {
/* Truncate page data and move it into the tail */
- xdr_shrink_pagelen(buf, buf->page_len - len);
+ offset = buf->page_len - len;
+ copied = xdr_shrink_pagelen(buf, offset);
+ trace_rpc_xdr_alignment(xdr, offset, copied);
xdr->nwords = XDR_QUADLEN(buf->len - cur);
}
return len;