diff options
Diffstat (limited to 'libnetdata/onewayalloc')
| -rw-r--r-- | libnetdata/onewayalloc/Makefile.am | 8 | ||||
| -rw-r--r-- | libnetdata/onewayalloc/README.md | 71 | ||||
| -rw-r--r-- | libnetdata/onewayalloc/onewayalloc.c | 178 | ||||
| -rw-r--r-- | libnetdata/onewayalloc/onewayalloc.h | 17 |
4 files changed, 274 insertions, 0 deletions
diff --git a/libnetdata/onewayalloc/Makefile.am b/libnetdata/onewayalloc/Makefile.am new file mode 100644 index 000000000..161784b8f --- /dev/null +++ b/libnetdata/onewayalloc/Makefile.am @@ -0,0 +1,8 @@ +# SPDX-License-Identifier: GPL-3.0-or-later + +AUTOMAKE_OPTIONS = subdir-objects +MAINTAINERCLEANFILES = $(srcdir)/Makefile.in + +dist_noinst_DATA = \ + README.md \ + $(NULL) diff --git a/libnetdata/onewayalloc/README.md b/libnetdata/onewayalloc/README.md new file mode 100644 index 000000000..1f459c263 --- /dev/null +++ b/libnetdata/onewayalloc/README.md @@ -0,0 +1,71 @@ +<!-- +title: "One Way Allocator" +custom_edit_url: https://github.com/netdata/netdata/edit/master/libnetdata/onewayallocator/README.md +--> + +# One Way Allocator + +This is a very fast single-threaded-only memory allocator, that minimized system calls +when a lot of memory allocations needs to be made to perform a task, which all of them +can be freed together when the task finishes. + +It has been designed to be used for netdata context queries. + +For netdata to perform a context query, it builds a virtual chart, a chart that contains +all the dimensions of the charts having the same context. This process requires allocating +several structures for each of the dimensions to attach them to the virtual chart. All +these data can be freed immediately after the query finishes. + +## How it works + +1. The caller calls `ONEWAYALLOC *owa = onewayalloc_create(sizehint)` to create an OWA. + Internally this allocates the first memory buffer with size >= `sizehint`. + If `sizehint` is zero, it will allocate 1 hardware page (usually 4kb). + No need to check for success or failure. As with `mallocz()` in netdata, a `fatal()` + will be called if the allocation fails - although this will never fail, since Linux + does not really check if there is memory available for `mmap()` calls. + +2. The caller can then perform any number of the following calls to acquire memory: + - `onewayalloc_mallocz(owa, size)`, similar to `mallocz()` + - `onewayalloc_callocz(owa, nmemb, size)`, similar to `callocz()` + - `onewayalloc_strdupz(owa, string)`, similar to `strdupz()` + - `onewayalloc_memdupz(owa, ptr, size)`, similar to `mallocz()` and then `memcpy()` + +3. Once the caller has done all the work with the allocated buffers, all memory allocated + can be freed with `onewayalloc_destroy(owa)`. + +## How faster it is? + +On modern hardware, for any single query the performance improvement is marginal and not +noticeable at all. + +We performed the following tests using the same huge context query (1000 charts, +100 dimensions each = 100k dimensions) + +1. using `mallocz()`, 1 caller, 256 queries (sequential) +2. using `mallocz()`, 256 callers, 1 query each (parallel) +3. using `OWA`, 1 caller, 256 queries (sequential) +4. using `OWA`, 256 callers, 1 query each (parallel) + +Netdata was configured to use 24 web threads on the 24 core server we used. + +The results are as follows: + +### sequential test + +branch|transactions|time to complete|transaction rate|average response time|min response time|max response time +:---:|:---:|:---:|:---:|:---:|:---:|:---:| +`malloc()`|256|322.35s|0.79/sec|1.26s|1.01s|1.87s +`OWA`|256|310.19s|0.83/sec|1.21s|1.04s|1.63s + +For a single query, the improvement is just marginal and not noticeable at all. + +### parallel test + +branch|transactions|time to complete|transaction rate|average response time|min response time|max response time +:---:|:---:|:---:|:---:|:---:|:---:|:---:| +`malloc()`|256|84.72s|3.02/sec|68.43s|50.20s|84.71s +`OWA`|256|39.35s|6.51/sec|34.48s|20.55s|39.34s + +For parallel workload, like the one executed by netdata.cloud, `OWA` provides a 54% overall speed improvement (more than double the overall +user-experienced speed, including the data query itself). diff --git a/libnetdata/onewayalloc/onewayalloc.c b/libnetdata/onewayalloc/onewayalloc.c new file mode 100644 index 000000000..a048aebf6 --- /dev/null +++ b/libnetdata/onewayalloc/onewayalloc.c @@ -0,0 +1,178 @@ +#include "onewayalloc.h" + +static size_t OWA_NATURAL_PAGE_SIZE = 0; +static size_t OWA_NATURAL_ALIGNMENT = sizeof(int*); + +typedef struct owa_page { + size_t stats_pages; + size_t stats_pages_size; + size_t stats_mallocs_made; + size_t stats_mallocs_size; + size_t size; // the total size of the page + size_t offset; // the first free byte of the page + struct owa_page *next; // the next page on the list + struct owa_page *last; // the last page on the list - we currently allocate on this +} OWA_PAGE; + +// allocations need to be aligned to CPU register width +// https://en.wikipedia.org/wiki/Data_structure_alignment +static inline size_t natural_alignment(size_t size) { + if(unlikely(size % OWA_NATURAL_ALIGNMENT)) + size = size + OWA_NATURAL_ALIGNMENT - (size % OWA_NATURAL_ALIGNMENT); + + return size; +} + +// Create an OWA +// Once it is created, the called may call the onewayalloc_mallocz() +// any number of times, for any amount of memory. + +static OWA_PAGE *onewayalloc_create_internal(OWA_PAGE *head, size_t size_hint) { + if(unlikely(!OWA_NATURAL_PAGE_SIZE)) + OWA_NATURAL_PAGE_SIZE = sysconf(_SC_PAGE_SIZE); + + // our default page size + size_t size = OWA_NATURAL_PAGE_SIZE; + + // make sure the new page will fit both the requested size + // and the OWA_PAGE structure at its beginning + size_hint += sizeof(OWA_PAGE); + + // prefer the user size if it is bigger than our size + if(size_hint > size) size = size_hint; + + // try to allocate half of the total we have allocated already + if(likely(head)) { + size_t optimal_size = head->stats_pages_size / 2; + if(optimal_size > size) size = optimal_size; + } + + // Make sure our allocations are always a multiple of the hardware page size + if(size % OWA_NATURAL_PAGE_SIZE) size = size + OWA_NATURAL_PAGE_SIZE - (size % OWA_NATURAL_PAGE_SIZE); + + // OWA_PAGE *page = (OWA_PAGE *)netdata_mmap(NULL, size, MAP_ANONYMOUS|MAP_PRIVATE, 0); + // if(unlikely(!page)) fatal("Cannot allocate onewayalloc buffer of size %zu", size); + OWA_PAGE *page = (OWA_PAGE *)mallocz(size); + + page->size = size; + page->offset = natural_alignment(sizeof(OWA_PAGE)); + page->next = page->last = NULL; + + if(unlikely(!head)) { + // this is the first time we are called + head = page; + head->stats_pages = 0; + head->stats_pages_size = 0; + head->stats_mallocs_made = 0; + head->stats_mallocs_size = 0; + } + else { + // link this page into our existing linked list + head->last->next = page; + } + + head->last = page; + head->stats_pages++; + head->stats_pages_size += size; + + return (ONEWAYALLOC *)page; +} + +ONEWAYALLOC *onewayalloc_create(size_t size_hint) { + return onewayalloc_create_internal(NULL, size_hint); +} + +void *onewayalloc_mallocz(ONEWAYALLOC *owa, size_t size) { + OWA_PAGE *head = (OWA_PAGE *)owa; + OWA_PAGE *page = head->last; + + // update stats + head->stats_mallocs_made++; + head->stats_mallocs_size += size; + + // make sure the size is aligned + size = natural_alignment(size); + + if(unlikely(page->size - page->offset < size)) { + // we don't have enough space to fit the data + // let's get another page + page = onewayalloc_create_internal(head, (size > page->size)?size:page->size); + } + + char *mem = (char *)page; + mem = &mem[page->offset]; + page->offset += size; + + return (void *)mem; +} + +void *onewayalloc_callocz(ONEWAYALLOC *owa, size_t nmemb, size_t size) { + size_t total = nmemb * size; + void *mem = onewayalloc_mallocz(owa, total); + memset(mem, 0, total); + return mem; +} + +char *onewayalloc_strdupz(ONEWAYALLOC *owa, const char *s) { + size_t size = strlen(s) + 1; + char *d = onewayalloc_mallocz((OWA_PAGE *)owa, size); + memcpy(d, s, size); + return d; +} + +void *onewayalloc_memdupz(ONEWAYALLOC *owa, const void *src, size_t size) { + void *mem = onewayalloc_mallocz((OWA_PAGE *)owa, size); + // memcpy() is way faster than strcpy() since it does not check for '\0' + memcpy(mem, src, size); + return mem; +} + +void onewayalloc_freez(ONEWAYALLOC *owa __maybe_unused, const void *ptr __maybe_unused) { +#ifdef NETDATA_INTERNAL_CHECKS + // allow the caller to call us for a mallocz() allocation + // so try to find it in our memory and if it is not there + // log an error + + if (unlikely(!ptr)) + return; + + OWA_PAGE *head = (OWA_PAGE *)owa; + OWA_PAGE *page; + size_t seeking = (size_t)ptr; + + for(page = head; page ;page = page->next) { + size_t start = (size_t)page; + size_t end = start + page->size; + + if(seeking >= start && seeking <= end) { + // found it - it is ours + // just return to let the caller think we actually did something + return; + } + } + + // not found - it is not ours + // let's free it with the system allocator + error("ONEWAYALLOC: request to free address 0x%p that is not allocated by this OWA", ptr); +#endif + + return; +} + +void onewayalloc_destroy(ONEWAYALLOC *owa) { + if(!owa) return; + + OWA_PAGE *head = (OWA_PAGE *)owa; + + //info("OWA: %zu allocations of %zu total bytes, in %zu pages of %zu total bytes", + // head->stats_mallocs_made, head->stats_mallocs_size, + // head->stats_pages, head->stats_pages_size); + + OWA_PAGE *page = head; + while(page) { + OWA_PAGE *p = page; + page = page->next; + // munmap(p, p->size); + freez(p); + } +} diff --git a/libnetdata/onewayalloc/onewayalloc.h b/libnetdata/onewayalloc/onewayalloc.h new file mode 100644 index 000000000..ed8f12f39 --- /dev/null +++ b/libnetdata/onewayalloc/onewayalloc.h @@ -0,0 +1,17 @@ +#ifndef ONEWAYALLOC_H +#define ONEWAYALLOC_H 1 + +#include "../libnetdata.h" + +typedef void ONEWAYALLOC; + +extern ONEWAYALLOC *onewayalloc_create(size_t size_hint); +extern void onewayalloc_destroy(ONEWAYALLOC *owa); + +extern void *onewayalloc_mallocz(ONEWAYALLOC *owa, size_t size); +extern void *onewayalloc_callocz(ONEWAYALLOC *owa, size_t nmemb, size_t size); +extern char *onewayalloc_strdupz(ONEWAYALLOC *owa, const char *s); +extern void *onewayalloc_memdupz(ONEWAYALLOC *owa, const void *src, size_t size); +extern void onewayalloc_freez(ONEWAYALLOC *owa, const void *ptr); + +#endif // ONEWAYALLOC_H |