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# Short description
The Redis extended latency stats track per command latencies and enables:
- exporting the per-command percentile distribution via the `INFO LATENCYSTATS` command.
**( percentile distribution is not mergeable between cluster nodes ).**
- exporting the per-command cumulative latency distributions via the `LATENCY HISTOGRAM` command.
Using the cumulative distribution of latencies we can merge several stats from different cluster nodes
to calculate aggregate metrics .
By default, the extended latency monitoring is enabled since the overhead of keeping track of the
command latency is very small.
If you don't want to track extended latency metrics, you can easily disable it at runtime using the command:
- `CONFIG SET latency-tracking no`
By default, the exported latency percentiles are the p50, p99, and p999.
You can alter them at runtime using the command:
- `CONFIG SET latency-tracking-info-percentiles "0.0 50.0 100.0"`
## Some details:
- The total size per histogram should sit around 40 KiB. We only allocate those 40KiB when a command
was called for the first time.
- With regards to the WRITE overhead As seen below, there is no measurable overhead on the achievable
ops/sec or full latency spectrum on the client. Including also the measured redis-benchmark for unstable
vs this branch.
- We track from 1 nanosecond to 1 second ( everything above 1 second is considered +Inf )
## `INFO LATENCYSTATS` exposition format
- Format: `latency_percentiles_usec_<CMDNAME>:p0=XX,p50....`
## `LATENCY HISTOGRAM [command ...]` exposition format
Return a cumulative distribution of latencies in the format of a histogram for the specified command names.
The histogram is composed of a map of time buckets:
- Each representing a latency range, between 1 nanosecond and roughly 1 second.
- Each bucket covers twice the previous bucket's range.
- Empty buckets are not printed.
- Everything above 1 sec is considered +Inf.
- At max there will be log2(1000000000)=30 buckets
We reply a map for each command in the format:
`<command name> : { `calls`: <total command calls> , `histogram` : { <bucket 1> : latency , < bucket 2> : latency, ... } }`
Co-authored-by: Oran Agra <oran@redislabs.com>
144 lines
5.2 KiB
C
144 lines
5.2 KiB
C
/* zmalloc - total amount of allocated memory aware version of malloc()
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*
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* Copyright (c) 2009-2010, Salvatore Sanfilippo <antirez at gmail dot com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Redis nor the names of its contributors may be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __ZMALLOC_H
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#define __ZMALLOC_H
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/* Double expansion needed for stringification of macro values. */
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#define __xstr(s) __str(s)
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#define __str(s) #s
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#if defined(USE_TCMALLOC)
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#define ZMALLOC_LIB ("tcmalloc-" __xstr(TC_VERSION_MAJOR) "." __xstr(TC_VERSION_MINOR))
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#include <google/tcmalloc.h>
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#if (TC_VERSION_MAJOR == 1 && TC_VERSION_MINOR >= 6) || (TC_VERSION_MAJOR > 1)
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#define HAVE_MALLOC_SIZE 1
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#define zmalloc_size(p) tc_malloc_size(p)
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#else
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#error "Newer version of tcmalloc required"
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#endif
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#elif defined(USE_JEMALLOC)
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#define ZMALLOC_LIB ("jemalloc-" __xstr(JEMALLOC_VERSION_MAJOR) "." __xstr(JEMALLOC_VERSION_MINOR) "." __xstr(JEMALLOC_VERSION_BUGFIX))
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#include <jemalloc/jemalloc.h>
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#if (JEMALLOC_VERSION_MAJOR == 2 && JEMALLOC_VERSION_MINOR >= 1) || (JEMALLOC_VERSION_MAJOR > 2)
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#define HAVE_MALLOC_SIZE 1
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#define zmalloc_size(p) je_malloc_usable_size(p)
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#else
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#error "Newer version of jemalloc required"
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#endif
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#elif defined(__APPLE__)
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#include <malloc/malloc.h>
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#define HAVE_MALLOC_SIZE 1
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#define zmalloc_size(p) malloc_size(p)
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#endif
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/* On native libc implementations, we should still do our best to provide a
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* HAVE_MALLOC_SIZE capability. This can be set explicitly as well:
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*
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* NO_MALLOC_USABLE_SIZE disables it on all platforms, even if they are
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* known to support it.
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* USE_MALLOC_USABLE_SIZE forces use of malloc_usable_size() regardless
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* of platform.
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*/
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#ifndef ZMALLOC_LIB
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#define ZMALLOC_LIB "libc"
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#if !defined(NO_MALLOC_USABLE_SIZE) && \
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(defined(__GLIBC__) || defined(__FreeBSD__) || \
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defined(USE_MALLOC_USABLE_SIZE))
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/* Includes for malloc_usable_size() */
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#ifdef __FreeBSD__
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#include <malloc_np.h>
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#else
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#include <malloc.h>
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#endif
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#define HAVE_MALLOC_SIZE 1
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#define zmalloc_size(p) malloc_usable_size(p)
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#endif
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#endif
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/* We can enable the Redis defrag capabilities only if we are using Jemalloc
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* and the version used is our special version modified for Redis having
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* the ability to return per-allocation fragmentation hints. */
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#if defined(USE_JEMALLOC) && defined(JEMALLOC_FRAG_HINT)
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#define HAVE_DEFRAG
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#endif
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void *zmalloc(size_t size);
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void *zcalloc(size_t size);
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void *zcalloc_num(size_t num, size_t size);
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void *zrealloc(void *ptr, size_t size);
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void *ztrymalloc(size_t size);
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void *ztrycalloc(size_t size);
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void *ztryrealloc(void *ptr, size_t size);
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void zfree(void *ptr);
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void *zmalloc_usable(size_t size, size_t *usable);
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void *zcalloc_usable(size_t size, size_t *usable);
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void *zrealloc_usable(void *ptr, size_t size, size_t *usable);
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void *ztrymalloc_usable(size_t size, size_t *usable);
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void *ztrycalloc_usable(size_t size, size_t *usable);
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void *ztryrealloc_usable(void *ptr, size_t size, size_t *usable);
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void zfree_usable(void *ptr, size_t *usable);
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char *zstrdup(const char *s);
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size_t zmalloc_used_memory(void);
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void zmalloc_set_oom_handler(void (*oom_handler)(size_t));
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size_t zmalloc_get_rss(void);
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int zmalloc_get_allocator_info(size_t *allocated, size_t *active, size_t *resident);
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void set_jemalloc_bg_thread(int enable);
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int jemalloc_purge();
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size_t zmalloc_get_private_dirty(long pid);
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size_t zmalloc_get_smap_bytes_by_field(char *field, long pid);
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size_t zmalloc_get_memory_size(void);
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void zlibc_free(void *ptr);
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void zmadvise_dontneed(void *ptr);
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#ifdef HAVE_DEFRAG
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void zfree_no_tcache(void *ptr);
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void *zmalloc_no_tcache(size_t size);
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#endif
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#ifndef HAVE_MALLOC_SIZE
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size_t zmalloc_size(void *ptr);
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size_t zmalloc_usable_size(void *ptr);
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#else
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#define zmalloc_usable_size(p) zmalloc_size(p)
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#endif
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#ifdef REDIS_TEST
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int zmalloc_test(int argc, char **argv, int flags);
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#endif
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#endif /* __ZMALLOC_H */
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