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netfs: Gather stats
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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-and-tested-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Dave Wysochanski <dwysocha@redhat.com>
Tested-By: Marc Dionne <marc.dionne@auristor.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
Link: https://lore.kernel.org/r/161118139247.1232039.10556850937548511068.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161161034669.2537118.2761232524997091480.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/161340397101.1303470.17581910581108378458.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/161539539959.286939.6794352576462965914.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/161653797700.2770958.5801990354413178228.stgit@warthog.procyon.org.uk/ # v5
Link: https://lore.kernel.org/r/161789079281.6155.17141344853277186500.stgit@warthog.procyon.org.uk/ # v6
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@dhowells
dhowells committed Apr 23, 2021
1 parent 77b4d2c commit 289af54
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Showing 6 changed files with 128 additions and 2 deletions.
15 changes: 15 additions & 0 deletions fs/netfs/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
3 changes: 1 addition & 2 deletions fs/netfs/Makefile
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Original file line number Diff line number Diff line change
@@ -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
34 changes: 34 additions & 0 deletions fs/netfs/internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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

/*****************************************************************************/
/*
Expand Down
23 changes: 23 additions & 0 deletions fs/netfs/read_helper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@ 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;
Expand Down Expand Up @@ -88,6 +89,7 @@ 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, bool was_async)
Expand Down Expand Up @@ -117,6 +119,7 @@ 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;
Expand All @@ -134,6 +137,7 @@ static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,

trace_netfs_sreq(subreq, netfs_sreq_trace_free);
kfree(subreq);
netfs_stat_d(&netfs_n_rh_sreq);
netfs_put_read_request(rreq, was_async);
}

Expand All @@ -156,6 +160,7 @@ 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, false);
}
Expand All @@ -179,6 +184,7 @@ 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);
}

Expand Down Expand Up @@ -288,6 +294,7 @@ 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);
Expand Down Expand Up @@ -319,6 +326,7 @@ 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);
Expand Down Expand Up @@ -414,6 +422,17 @@ 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;
Expand Down Expand Up @@ -470,8 +489,10 @@ 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;
}
Expand Down Expand Up @@ -653,6 +674,7 @@ 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);

Expand Down Expand Up @@ -722,6 +744,7 @@ int netfs_readpage(struct file *file,
rreq->start = page_index(page) * 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);
Expand Down
54 changes: 54 additions & 0 deletions fs/netfs/stats.c
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Original file line number Diff line number Diff line change
@@ -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);
1 change: 1 addition & 0 deletions include/linux/netfs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -166,5 +166,6 @@ extern int netfs_readpage(struct file *,
void *);

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

#endif /* _LINUX_NETFS_H */

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