Mercurial > hg > nginx
view src/core/ngx_queue.c @ 9167:3038bd4d7816
Core: changed ngx_queue_sort() to use merge sort.
This improves nginx startup times significantly when using very large number
of locations due to computational complexity of the sorting algorithm being
used: insertion sort is O(n*n) on average, while merge sort is O(n*log(n)).
In particular, in a test configuration with 20k locations total startup
time is reduced from 8 seconds to 0.9 seconds.
Prodded by Yusuke Nojima,
https://mailman.nginx.org/pipermail/nginx-devel/2023-September/NUL3Y2FPPFSHMPTFTL65KXSXNTX3NQMK.html
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Wed, 18 Oct 2023 04:30:11 +0300 |
parents | d620f497c50f |
children |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> static void ngx_queue_merge(ngx_queue_t *queue, ngx_queue_t *tail, ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *)); /* * find the middle queue element if the queue has odd number of elements * or the first element of the queue's second part otherwise */ ngx_queue_t * ngx_queue_middle(ngx_queue_t *queue) { ngx_queue_t *middle, *next; middle = ngx_queue_head(queue); if (middle == ngx_queue_last(queue)) { return middle; } next = ngx_queue_head(queue); for ( ;; ) { middle = ngx_queue_next(middle); next = ngx_queue_next(next); if (next == ngx_queue_last(queue)) { return middle; } next = ngx_queue_next(next); if (next == ngx_queue_last(queue)) { return middle; } } } /* the stable merge sort */ void ngx_queue_sort(ngx_queue_t *queue, ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *)) { ngx_queue_t *q, tail; q = ngx_queue_head(queue); if (q == ngx_queue_last(queue)) { return; } q = ngx_queue_middle(queue); ngx_queue_split(queue, q, &tail); ngx_queue_sort(queue, cmp); ngx_queue_sort(&tail, cmp); ngx_queue_merge(queue, &tail, cmp); } static void ngx_queue_merge(ngx_queue_t *queue, ngx_queue_t *tail, ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *)) { ngx_queue_t *q1, *q2; q1 = ngx_queue_head(queue); q2 = ngx_queue_head(tail); for ( ;; ) { if (q1 == ngx_queue_sentinel(queue)) { ngx_queue_add(queue, tail); break; } if (q2 == ngx_queue_sentinel(tail)) { break; } if (cmp(q1, q2) <= 0) { q1 = ngx_queue_next(q1); continue; } ngx_queue_remove(q2); ngx_queue_insert_before(q1, q2); q2 = ngx_queue_head(tail); } }