freebsd-nq/lib/libnvpair/libnvpair_json.c
Serapheim Dimitropoulos 6b64382b17 OpenZFS 9580 - Add a hash-table on top of nvlist to speed-up operations
= Motivation

While dealing with another performance issue (see 126118f) we noticed
that we spend a lot of time in various places in the kernel when
constructing long nvlists. The problem is that when an nvlist is created
with the NV_UNIQUE_NAME set (which is the case most of the time), we do
a linear search through the whole list to ensure uniqueness for every
entry we add.

An example of the above scenario can be seen in the following
flamegraph, where more than have the time of the zfsdev_ioctl() is spent
on constructing nvlists.  Flamegraph:
https://sdimitro.github.io/img/flame/sdimitro_snap_unmount3.svg

Adding a table to speed up lookups will help situations where we just
construct an nvlist (like the scenario above), in addition to regular
lookups and removals.

= What this patch does

In this diff we've implemented a hash-table on top of the nvlist code
that converts most nvlist operations from O(# number of entries) to
O(1)* (the start is for amortized time as the hash-table grows and
shrinks depending on the # of entries - plain lookup is strictly O(1)).

= Performance Analysis

To analyze the performance improvement I just used the setup from the
snapshot deletion issue mentioned above in the Motivation section.
Basically I created 10K filesystems with one snapshot each and then I
just used the API of libZFS_Core to pass down an nvlist of all the
snapshots to have them deleted. The reason I used my own driver program
was to have clean performance results of what actually happens in the
kernel. The flamegraphs and wall clock times mentioned below were
gathered from the start to the end of the driver program's run. Between
trials the testpool used was completely destroyed, the system was
rebooted and the testpool was completely recreated. The reason for this
dance was to get consistent results.

== Results (before patch):

=== Sampling Flamegraphs

[Trial 1] https://sdimitro.github.io/img/flame/DLPX-53417/trial-A.svg
[Trial 2] https://sdimitro.github.io/img/flame/DLPX-53417/trial-A2.svg
[Trial 3] https://sdimitro.github.io/img/flame/DLPX-53417/trial-A3.svg

=== Wall clock times (in seconds)

```
[Trial 4]
real        5.3
user        0.4
sys         2.3

[Trial 5]
real        8.2
user        0.4
sys         2.4

[Trial 6]
real        6.0
user        0.5
sys         2.3
```

== Results (after patch):

=== Sampling Flamegraphs

[Trial 1] https://sdimitro.github.io/img/flame/DLPX-53417/trial-Ae.svg
[Trial 2] https://sdimitro.github.io/img/flame/DLPX-53417/trial-A2e.svg
[Trial 3] https://sdimitro.github.io/img/flame/DLPX-53417/trial-A3e.svg

=== Wall clock times (in seconds)

```
[Trial 4]
real        4.9
user        0.0
sys         0.9

[Trial 5]
real        3.8
user        0.0
sys         0.9

[Trial 6]
real        3.6
user        0.0
sys         0.9
```

== Analysis

The results between the trials are consistent so in this sections I will
only talk about the flamegraph results from trial-1 and the wall-clock
results from trial-4.

From trial-1 we can see that zfs_dev_ioctl() goes from 2,331 to 996
samples counts.  Specifically, the samples from fnvlist_add_nvlist() and
spa_history_log_nvl() are almost gone (~500 & ~800 to 5 & 5 samples),
leaving zfs_ioc_destroy_snaps() to dominate most samples from
zfs_dev_ioctl().

From trial-4 we see that the user time dropped to 0 secods. I believe
the consistent 0.4 seconds before my patch was applied was due to my
driver program constructing the long nvlist of snapshots so it can pass
it to the kernel. As for the system time, the effect there is more clear
(2.3 down to 0.9 seconds).

Porting Notes:
* DATA_TYPE_DONTCARE case added to switch in fm_nvprintr() and
  zpool_do_events_nvprint().

Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/9580
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/b5eca7b1
Closes #7748
2018-07-30 11:30:03 -07:00

407 lines
8.5 KiB
C

/*
* This file and its contents are supplied under the terms of the
* Common Development and Distribution License ("CDDL"), version 1.0.
* You may only use this file in accordance with the terms of version
* 1.0 of the CDDL.
*
* A full copy of the text of the CDDL should have accompanied this
* source. A copy of the CDDL is also available via the Internet at
* http://www.illumos.org/license/CDDL.
*/
/*
* Copyright (c) 2014, Joyent, Inc.
* Copyright (c) 2017 by Delphix. All rights reserved.
*/
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <wchar.h>
#include <sys/debug.h>
#include "libnvpair.h"
#define FPRINTF(fp, ...) \
do { \
if (fprintf(fp, __VA_ARGS__) < 0) \
return (-1); \
} while (0)
/*
* When formatting a string for JSON output we must escape certain characters,
* as described in RFC4627. This applies to both member names and
* DATA_TYPE_STRING values.
*
* This function will only operate correctly if the following conditions are
* met:
*
* 1. The input String is encoded in the current locale.
*
* 2. The current locale includes the Basic Multilingual Plane (plane 0)
* as defined in the Unicode standard.
*
* The output will be entirely 7-bit ASCII (as a subset of UTF-8) with all
* representable Unicode characters included in their escaped numeric form.
*/
static int
nvlist_print_json_string(FILE *fp, const char *input)
{
mbstate_t mbr;
wchar_t c;
size_t sz;
bzero(&mbr, sizeof (mbr));
FPRINTF(fp, "\"");
while ((sz = mbrtowc(&c, input, MB_CUR_MAX, &mbr)) > 0) {
switch (c) {
case '"':
FPRINTF(fp, "\\\"");
break;
case '\n':
FPRINTF(fp, "\\n");
break;
case '\r':
FPRINTF(fp, "\\r");
break;
case '\\':
FPRINTF(fp, "\\\\");
break;
case '\f':
FPRINTF(fp, "\\f");
break;
case '\t':
FPRINTF(fp, "\\t");
break;
case '\b':
FPRINTF(fp, "\\b");
break;
default:
if ((c >= 0x00 && c <= 0x1f) ||
(c > 0x7f && c <= 0xffff)) {
/*
* Render both Control Characters and Unicode
* characters in the Basic Multilingual Plane
* as JSON-escaped multibyte characters.
*/
FPRINTF(fp, "\\u%04x", (int)(0xffff & c));
} else if (c >= 0x20 && c <= 0x7f) {
/*
* Render other 7-bit ASCII characters directly
* and drop other, unrepresentable characters.
*/
FPRINTF(fp, "%c", (int)(0xff & c));
}
break;
}
input += sz;
}
if (sz == (size_t)-1 || sz == (size_t)-2) {
/*
* We last read an invalid multibyte character sequence,
* so return an error.
*/
return (-1);
}
FPRINTF(fp, "\"");
return (0);
}
/*
* Dump a JSON-formatted representation of an nvlist to the provided FILE *.
* This routine does not output any new-lines or additional whitespace other
* than that contained in strings, nor does it call fflush(3C).
*/
int
nvlist_print_json(FILE *fp, nvlist_t *nvl)
{
nvpair_t *curr;
boolean_t first = B_TRUE;
FPRINTF(fp, "{");
for (curr = nvlist_next_nvpair(nvl, NULL); curr;
curr = nvlist_next_nvpair(nvl, curr)) {
data_type_t type = nvpair_type(curr);
if (!first)
FPRINTF(fp, ",");
else
first = B_FALSE;
if (nvlist_print_json_string(fp, nvpair_name(curr)) == -1)
return (-1);
FPRINTF(fp, ":");
switch (type) {
case DATA_TYPE_STRING: {
char *string = fnvpair_value_string(curr);
if (nvlist_print_json_string(fp, string) == -1)
return (-1);
break;
}
case DATA_TYPE_BOOLEAN: {
FPRINTF(fp, "true");
break;
}
case DATA_TYPE_BOOLEAN_VALUE: {
FPRINTF(fp, "%s", fnvpair_value_boolean_value(curr) ==
B_TRUE ? "true" : "false");
break;
}
case DATA_TYPE_BYTE: {
FPRINTF(fp, "%hhu", fnvpair_value_byte(curr));
break;
}
case DATA_TYPE_INT8: {
FPRINTF(fp, "%hhd", fnvpair_value_int8(curr));
break;
}
case DATA_TYPE_UINT8: {
FPRINTF(fp, "%hhu", fnvpair_value_uint8(curr));
break;
}
case DATA_TYPE_INT16: {
FPRINTF(fp, "%hd", fnvpair_value_int16(curr));
break;
}
case DATA_TYPE_UINT16: {
FPRINTF(fp, "%hu", fnvpair_value_uint16(curr));
break;
}
case DATA_TYPE_INT32: {
FPRINTF(fp, "%d", fnvpair_value_int32(curr));
break;
}
case DATA_TYPE_UINT32: {
FPRINTF(fp, "%u", fnvpair_value_uint32(curr));
break;
}
case DATA_TYPE_INT64: {
FPRINTF(fp, "%lld",
(long long)fnvpair_value_int64(curr));
break;
}
case DATA_TYPE_UINT64: {
FPRINTF(fp, "%llu",
(unsigned long long)fnvpair_value_uint64(curr));
break;
}
case DATA_TYPE_HRTIME: {
hrtime_t val;
VERIFY0(nvpair_value_hrtime(curr, &val));
FPRINTF(fp, "%llu", (unsigned long long)val);
break;
}
case DATA_TYPE_DOUBLE: {
double val;
VERIFY0(nvpair_value_double(curr, &val));
FPRINTF(fp, "%f", val);
break;
}
case DATA_TYPE_NVLIST: {
if (nvlist_print_json(fp,
fnvpair_value_nvlist(curr)) == -1)
return (-1);
break;
}
case DATA_TYPE_STRING_ARRAY: {
char **val;
uint_t valsz, i;
VERIFY0(nvpair_value_string_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
if (nvlist_print_json_string(fp, val[i]) == -1)
return (-1);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_NVLIST_ARRAY: {
nvlist_t **val;
uint_t valsz, i;
VERIFY0(nvpair_value_nvlist_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
if (nvlist_print_json(fp, val[i]) == -1)
return (-1);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_BOOLEAN_ARRAY: {
boolean_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_boolean_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, val[i] == B_TRUE ?
"true" : "false");
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_BYTE_ARRAY: {
uchar_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_byte_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%hhu", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_UINT8_ARRAY: {
uint8_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_uint8_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%hhu", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_INT8_ARRAY: {
int8_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_int8_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%hd", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_UINT16_ARRAY: {
uint16_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_uint16_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%hu", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_INT16_ARRAY: {
int16_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_int16_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%hd", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_UINT32_ARRAY: {
uint32_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_uint32_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%u", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_INT32_ARRAY: {
int32_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_int32_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%d", val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_UINT64_ARRAY: {
uint64_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_uint64_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%llu",
(unsigned long long)val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_INT64_ARRAY: {
int64_t *val;
uint_t valsz, i;
VERIFY0(nvpair_value_int64_array(curr, &val, &valsz));
FPRINTF(fp, "[");
for (i = 0; i < valsz; i++) {
if (i > 0)
FPRINTF(fp, ",");
FPRINTF(fp, "%lld", (long long)val[i]);
}
FPRINTF(fp, "]");
break;
}
case DATA_TYPE_UNKNOWN:
case DATA_TYPE_DONTCARE:
return (-1);
}
}
FPRINTF(fp, "}");
return (0);
}