[PATCH 10/33] netfs: Gather stats

David Howells
2021-02-15T15:46:24Z

Gather statistics from the netfs interface that can be exported through a
seqfile. This is intended to be called by a later patch when viewing
/proc/fs/fscache/stats.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

fs/netfs/Kconfig | 15 +++++++++++++
fs/netfs/Makefile | 3 +--
fs/netfs/internal.h | 34 ++++++++++++++++++++++++++++++
fs/netfs/read_helper.c | 23 ++++++++++++++++++++
fs/netfs/stats.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/netfs.h | 1 +
6 files changed, 128 insertions(+), 2 deletions(-)
create mode 100644 fs/netfs/stats.c

diff --git a/fs/netfs/Kconfig b/fs/netfs/Kconfig
index 2ebf90e6ca95..578112713703 100644
--- a/fs/netfs/Kconfig
+++ b/fs/netfs/Kconfig
@@ -6,3 +6,18 @@ config NETFS_SUPPORT
This option enables support for network filesystems, including
helpers for high-level buffered I/O, abstracting out read
segmentation, local caching and transparent huge page support.
+
+config NETFS_STATS
+ bool "Gather statistical information on local caching"
+ depends on NETFS_SUPPORT && PROC_FS
+ help
+ This option causes statistical information to be gathered on local
+ caching and exported through file:
+
+ /proc/fs/fscache/stats
+
+ The gathering of statistics adds a certain amount of overhead to
+ execution as there are a quite a few stats gathered, and on a
+ multi-CPU system these may be on cachelines that keep bouncing
+ between CPUs. On the other hand, the stats are very useful for
+ debugging purposes. Saying 'Y' here is recommended.
diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile
index 4b4eff2ba369..c15bfc966d96 100644
--- a/fs/netfs/Makefile
+++ b/fs/netfs/Makefile
@@ -1,6 +1,5 @@
# SPDX-License-Identifier: GPL-2.0

-netfs-y := \
- read_helper.o
+netfs-y := read_helper.o stats.o

obj-$(CONFIG_NETFS_SUPPORT) := netfs.o
diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index ee665c0e7dc8..98b6f4516da1 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -16,8 +16,42 @@
*/
extern unsigned int netfs_debug;

+/*
+ * stats.c
+ */
+#ifdef CONFIG_NETFS_STATS
+extern atomic_t netfs_n_rh_readahead;
+extern atomic_t netfs_n_rh_readpage;
+extern atomic_t netfs_n_rh_rreq;
+extern atomic_t netfs_n_rh_sreq;
+extern atomic_t netfs_n_rh_download;
+extern atomic_t netfs_n_rh_download_done;
+extern atomic_t netfs_n_rh_download_failed;
+extern atomic_t netfs_n_rh_download_instead;
+extern atomic_t netfs_n_rh_read;
+extern atomic_t netfs_n_rh_read_done;
+extern atomic_t netfs_n_rh_read_failed;
+extern atomic_t netfs_n_rh_zero;
+extern atomic_t netfs_n_rh_short_read;
+extern atomic_t netfs_n_rh_write;
+extern atomic_t netfs_n_rh_write_done;
+extern atomic_t netfs_n_rh_write_failed;
+
+
+static inline void netfs_stat(atomic_t *stat)
+{
+ atomic_inc(stat);
+}
+
+static inline void netfs_stat_d(atomic_t *stat)
+{
+ atomic_dec(stat);
+}
+
+#else
#define netfs_stat(x) do {} while(0)
#define netfs_stat_d(x) do {} while(0)
+#endif

/*****************************************************************************/
/*
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 53b04b105179..4f6f708f8f18 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -55,6 +55,7 @@ static struct netfs_read_request *netfs_alloc_read_request(
refcount_set(&rreq->usage, 1);
__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
ops->init_rreq(rreq, file);
+ netfs_stat(&netfs_n_rh_rreq);
}

return rreq;
@@ -86,6 +87,7 @@ static void netfs_free_read_request(struct work_struct *work)
rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
trace_netfs_rreq(rreq, netfs_rreq_trace_free);
kfree(rreq);
+ netfs_stat_d(&netfs_n_rh_rreq);
}

static void netfs_put_read_request(struct netfs_read_request *rreq)
@@ -115,6 +117,7 @@ static struct netfs_read_subrequest *netfs_alloc_subrequest(
refcount_set(&subreq->usage, 2);
subreq->rreq = rreq;
netfs_get_read_request(rreq);
+ netfs_stat(&netfs_n_rh_sreq);
}

return subreq;
@@ -130,6 +133,7 @@ static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
trace_netfs_sreq(subreq, netfs_sreq_trace_free);
netfs_put_read_request(subreq->rreq);
kfree(subreq);
+ netfs_stat_d(&netfs_n_rh_sreq);
}

/*
@@ -151,6 +155,7 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq)
{
+ netfs_stat(&netfs_n_rh_zero);
__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
netfs_subreq_terminated(subreq, 0);
}
@@ -174,6 +179,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
static void netfs_read_from_server(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq)
{
+ netfs_stat(&netfs_n_rh_download);
rreq->netfs_ops->issue_op(subreq);
}

@@ -283,6 +289,7 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq,
__clear_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
__set_bit(NETFS_SREQ_SEEK_DATA_READ, &subreq->flags);

+ netfs_stat(&netfs_n_rh_short_read);
trace_netfs_sreq(subreq, netfs_sreq_trace_resubmit_short);

netfs_get_read_subrequest(subreq);
@@ -314,6 +321,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
break;
subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
subreq->error = 0;
+ netfs_stat(&netfs_n_rh_download_instead);
trace_netfs_sreq(subreq, netfs_sreq_trace_download_instead);
netfs_get_read_subrequest(subreq);
atomic_inc(&rreq->nr_rd_ops);
@@ -406,6 +414,17 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
subreq->debug_index, subreq->start, subreq->flags,
transferred_or_error);

+ switch (subreq->source) {
+ case NETFS_READ_FROM_CACHE:
+ netfs_stat(&netfs_n_rh_read_done);
+ break;
+ case NETFS_DOWNLOAD_FROM_SERVER:
+ netfs_stat(&netfs_n_rh_download_done);
+ break;
+ default:
+ break;
+ }
+
if (IS_ERR_VALUE(transferred_or_error)) {
subreq->error = transferred_or_error;
goto failed;
@@ -459,8 +478,10 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,

failed:
if (subreq->source == NETFS_READ_FROM_CACHE) {
+ netfs_stat(&netfs_n_rh_read_failed);
set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
} else {
+ netfs_stat(&netfs_n_rh_download_failed);
set_bit(NETFS_RREQ_FAILED, &rreq->flags);
rreq->error = subreq->error;
}
@@ -642,6 +663,7 @@ void netfs_readahead(struct readahead_control *ractl,
rreq->start = readahead_pos(ractl);
rreq->len = readahead_length(ractl);

+ netfs_stat(&netfs_n_rh_readahead);
trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
netfs_read_trace_readahead);

@@ -716,6 +738,7 @@ int netfs_readpage(struct file *file,
rreq->start = page->index * PAGE_SIZE;
rreq->len = thp_size(page);

+ netfs_stat(&netfs_n_rh_readpage);
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);

netfs_get_read_request(rreq);
diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
new file mode 100644
index 000000000000..df6ff5718f25
--- /dev/null
+++ b/fs/netfs/stats.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Netfs support statistics
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/seq_file.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+atomic_t netfs_n_rh_readahead;
+atomic_t netfs_n_rh_readpage;
+atomic_t netfs_n_rh_rreq;
+atomic_t netfs_n_rh_sreq;
+atomic_t netfs_n_rh_download;
+atomic_t netfs_n_rh_download_done;
+atomic_t netfs_n_rh_download_failed;
+atomic_t netfs_n_rh_download_instead;
+atomic_t netfs_n_rh_read;
+atomic_t netfs_n_rh_read_done;
+atomic_t netfs_n_rh_read_failed;
+atomic_t netfs_n_rh_zero;
+atomic_t netfs_n_rh_short_read;
+atomic_t netfs_n_rh_write;
+atomic_t netfs_n_rh_write_done;
+atomic_t netfs_n_rh_write_failed;
+
+void netfs_stats_show(struct seq_file *m)
+{
+ seq_printf(m, "RdHelp : RA=%u RP=%u rr=%u sr=%u\n",
+ atomic_read(&netfs_n_rh_readahead),
+ atomic_read(&netfs_n_rh_readpage),
+ atomic_read(&netfs_n_rh_rreq),
+ atomic_read(&netfs_n_rh_sreq));
+ seq_printf(m, "RdHelp : ZR=%u sh=%u\n",
+ atomic_read(&netfs_n_rh_zero),
+ atomic_read(&netfs_n_rh_short_read));
+ seq_printf(m, "RdHelp : DL=%u ds=%u df=%u di=%u\n",
+ atomic_read(&netfs_n_rh_download),
+ atomic_read(&netfs_n_rh_download_done),
+ atomic_read(&netfs_n_rh_download_failed),
+ atomic_read(&netfs_n_rh_download_instead));
+ seq_printf(m, "RdHelp : RD=%u rs=%u rf=%u\n",
+ atomic_read(&netfs_n_rh_read),
+ atomic_read(&netfs_n_rh_read_done),
+ atomic_read(&netfs_n_rh_read_failed));
+ seq_printf(m, "RdHelp : WR=%u ws=%u wf=%u\n",
+ atomic_read(&netfs_n_rh_write),
+ atomic_read(&netfs_n_rh_write_done),
+ atomic_read(&netfs_n_rh_write_failed));
+}
+EXPORT_SYMBOL(netfs_stats_show);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 24083dc0adfa..b8237b6f17cb 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -134,5 +134,6 @@ extern int netfs_readpage(struct file *,
void *);

extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
+extern void netfs_stats_show(struct seq_file *);

#endif /* _LINUX_NETFS_H */