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SUNRPC: Add trace event that reports reply page vector alignment

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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>
This commit is contained in:
Chuck Lever
2019-02-11 11:24:16 -05:00
committed by Anna Schumaker
parent 5582863f45
commit 7be9cea360
2 changed files with 86 additions and 6 deletions
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59
include/trace/events/sunrpc.h
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@@ -321,6 +321,65 @@ TRACE_EVENT(rpc_xdr_overflow,
)
);
TRACE_EVENT(rpc_xdr_alignment,
TP_PROTO(
const struct xdr_stream *xdr,
size_t offset,
unsigned int copied
),
TP_ARGS(xdr, offset, copied),
TP_STRUCT__entry(
__field(unsigned int, task_id)
__field(unsigned int, client_id)
__field(int, version)
__field(size_t, offset)
__field(unsigned int, copied)
__field(const void *, head_base)
__field(size_t, head_len)
__field(const void *, tail_base)
__field(size_t, tail_len)
__field(unsigned int, page_len)
__field(unsigned int, len)
__string(progname,
xdr->rqst->rq_task->tk_client->cl_program->name)
__string(procedure,
xdr->rqst->rq_task->tk_msg.rpc_proc->p_name)
),
TP_fast_assign(
const struct rpc_task *task = xdr->rqst->rq_task;
__entry->task_id = task->tk_pid;
__entry->client_id = task->tk_client->cl_clid;
__assign_str(progname,
task->tk_client->cl_program->name)
__entry->version = task->tk_client->cl_vers;
__assign_str(procedure, task->tk_msg.rpc_proc->p_name)
__entry->offset = offset;
__entry->copied = copied;
__entry->head_base = xdr->buf->head[0].iov_base,
__entry->head_len = xdr->buf->head[0].iov_len,
__entry->page_len = xdr->buf->page_len,
__entry->tail_base = xdr->buf->tail[0].iov_base,
__entry->tail_len = xdr->buf->tail[0].iov_len,
__entry->len = xdr->buf->len;
),
TP_printk(
"task:%u@%u %sv%d %s offset=%zu copied=%u xdr=[%p,%zu]/%u/[%p,%zu]/%u\n",
__entry->task_id, __entry->client_id,
__get_str(progname), __entry->version, __get_str(procedure),
__entry->offset, __entry->copied,
__entry->head_base, __entry->head_len,
__entry->page_len,
__entry->tail_base, __entry->tail_len,
__entry->len
)
);
/*
* First define the enums in the below macros to be exported to userspace
* via TRACE_DEFINE_ENUM().