[RFC PATCH 49/76] netfs: Stats

From: David Howells
Date: Fri Nov 20 2020 - 10:14:43 EST

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---

fs/netfs/Kconfig | 15 ++++++++++++++
fs/netfs/Makefile | 3 +--
fs/netfs/internal.h | 34 +++++++++++++++++++++++++++++++
fs/netfs/read_helper.c | 32 +++++++++++++++++++++++++++--
fs/netfs/stats.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/netfs.h | 1 +
6 files changed, 134 insertions(+), 4 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 b07f43f9130e..d83317b1eb9d 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 21d3578c6979..e1ce197d8d18 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_put_read_request(struct netfs_read_request *rreq)
fscache_end_operation(&rreq->cache_resources);
trace_netfs_rreq(rreq, netfs_rreq_trace_free);
kfree(rreq);
+ netfs_stat_d(&netfs_n_rh_rreq);
}
}

@@ -102,6 +104,7 @@ static struct netfs_read_subrequest *netfs_alloc_subrequest(
INIT_LIST_HEAD(&subreq->rreq_link);
refcount_set(&subreq->usage, 2);
subreq->rreq = rreq;
+ netfs_stat(&netfs_n_rh_sreq);
}

return subreq;
@@ -117,6 +120,7 @@ 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);
}

/*
@@ -153,6 +157,7 @@ static void netfs_read_from_cache(struct netfs_read_request *rreq,
subreq->start + subreq->transferred,
subreq->len - subreq->transferred);

+ netfs_stat(&netfs_n_rh_read);
fscache_read(&rreq->cache_resources, subreq->start, &iter, seek_data,
netfs_cache_read_terminated, subreq);
}
@@ -163,6 +168,7 @@ static void netfs_read_from_cache(struct netfs_read_request *rreq,
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);
}
@@ -186,6 +192,7 @@ 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);
}

@@ -240,10 +247,13 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
struct netfs_read_subrequest *subreq = priv;
struct netfs_read_request *rreq = subreq->rreq;

- if (IS_ERR_VALUE(transferred_or_error))
+ if (IS_ERR_VALUE(transferred_or_error)) {
subreq->error = transferred_or_error;
- else
+ netfs_stat(&netfs_n_rh_write_failed);
+ } else {
subreq->error = 0;
+ netfs_stat(&netfs_n_rh_write_done);
+ }

trace_netfs_sreq(subreq, netfs_sreq_trace_write_term);

@@ -288,6 +298,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
netfs_put_subrequest(next);
}

+ netfs_stat(&netfs_n_rh_write);
trace_netfs_sreq(subreq, netfs_sreq_trace_write);

iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
@@ -415,6 +426,7 @@ 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);
@@ -449,6 +461,7 @@ 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);
@@ -563,6 +576,17 @@ 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;
@@ -616,8 +640,10 @@ 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;
}
@@ -822,6 +848,7 @@ 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);

@@ -897,6 +924,7 @@ 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, page->index * PAGE_SIZE, thp_size(page),
netfs_read_trace_readpage);

diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
new file mode 100644
index 000000000000..3a7a3c10e1cd
--- /dev/null
+++ b/fs/netfs/stats.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Netfs support statistics
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#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 c4276eb9914d..d9cd9a1d1f6d 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -98,5 +98,6 @@ 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 */

Next message: Daniel Borkmann: "Re: [PATCH] bpf: Check the return value of dev_get_by_index_rcu()"
Previous message: David Howells: "[RFC PATCH 47/76] fscache: Remove more obsolete stats"
In reply to: David Howells: "[RFC PATCH 47/76] fscache: Remove more obsolete stats"
Next in thread: David Howells: "[RFC PATCH 48/76] fscache: Always create /proc/fs/fscache/stats if configured"
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