view src/event/ngx_event_busy_lock.c @ 4233:aae172db7ac8

Event pipe: reduced number of file buffers used. If possible we now just extend already present file buffer in p->out chain instead of keeping ngx_buf_t for each buffer we've flushed to disk. This saves about 120 bytes of memory per buffer flushed to disk, and resolves high CPU usage observed in edge cases (due to coalescing these buffers on send).
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 31 Oct 2011 09:54:55 +0000
parents 4c43e25d11ea
children d620f497c50f
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>


static ngx_int_t ngx_event_busy_lock_look_cacheable(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx);
static void ngx_event_busy_lock_handler(ngx_event_t *ev);
static void ngx_event_busy_lock_posted_handler(ngx_event_t *ev);


/*
 * NGX_OK:     the busy lock is held
 * NGX_AGAIN:  the all busy locks are held but we will wait the specified time
 * NGX_BUSY:   ctx->timer == 0: there are many the busy locks
 *             ctx->timer != 0: there are many the waiting locks
 */

ngx_int_t
ngx_event_busy_lock(ngx_event_busy_lock_t *bl, ngx_event_busy_lock_ctx_t *ctx)
{
    ngx_int_t  rc;

    ngx_mutex_lock(bl->mutex);

    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ctx->event->log, 0,
                   "event busy lock: b:%d mb:%d",
                   bl->busy, bl->max_busy);

    if (bl->busy < bl->max_busy) {
        bl->busy++;

        rc = NGX_OK;

    } else if (ctx->timer && bl->waiting < bl->max_waiting) {
        bl->waiting++;
        ngx_add_timer(ctx->event, ctx->timer);
        ctx->event->handler = ngx_event_busy_lock_handler;

        if (bl->events) {
            bl->last->next = ctx;

        } else {
            bl->events = ctx;
        }

        bl->last = ctx;

        rc = NGX_AGAIN;

    } else {
        rc = NGX_BUSY;
    }

    ngx_mutex_unlock(bl->mutex);

    return rc;
}


ngx_int_t
ngx_event_busy_lock_cacheable(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx)
{
    ngx_int_t  rc;

    ngx_mutex_lock(bl->mutex);

    rc = ngx_event_busy_lock_look_cacheable(bl, ctx);

    ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ctx->event->log, 0,
                   "event busy lock: %d w:%d mw:%d",
                   rc, bl->waiting, bl->max_waiting);

    /*
     * NGX_OK:     no the same request, there is free slot and we locked it
     * NGX_BUSY:   no the same request and there is no free slot
     * NGX_AGAIN:  the same request is processing
     */

    if (rc == NGX_AGAIN) {

        if (ctx->timer && bl->waiting < bl->max_waiting) {
            bl->waiting++;
            ngx_add_timer(ctx->event, ctx->timer);
            ctx->event->handler = ngx_event_busy_lock_handler;

            if (bl->events == NULL) {
                bl->events = ctx;
            } else {
                bl->last->next = ctx;
            }
            bl->last = ctx;

        } else {
            rc = NGX_BUSY;
        }
    }

    ngx_mutex_unlock(bl->mutex);

    return rc;
}


void
ngx_event_busy_unlock(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx)
{
    ngx_event_t                *ev;
    ngx_event_busy_lock_ctx_t  *wakeup;

    ngx_mutex_lock(bl->mutex);

    if (bl->events) {
        wakeup = bl->events;
        bl->events = bl->events->next;

    } else {
        wakeup = NULL;
        bl->busy--;
    }

    /*
     * MP: all ctx's and their queue must be in shared memory,
     *     each ctx has pid to wake up
     */

    if (wakeup == NULL) {
        ngx_mutex_unlock(bl->mutex);
        return;
    }

    if (ctx->md5) {
        for (wakeup = bl->events; wakeup; wakeup = wakeup->next) {
            if (wakeup->md5 == NULL || wakeup->slot != ctx->slot) {
                continue;
            }

            wakeup->handler = ngx_event_busy_lock_posted_handler;
            wakeup->cache_updated = 1;

            ev = wakeup->event;

            ngx_post_event(ev, &ngx_posted_events);
        }

        ngx_mutex_unlock(bl->mutex);

    } else {
        bl->waiting--;

        ngx_mutex_unlock(bl->mutex);

        wakeup->handler = ngx_event_busy_lock_posted_handler;
        wakeup->locked = 1;

        ev = wakeup->event;

        if (ev->timer_set) {
            ngx_del_timer(ev);
        }

        ngx_post_event(ev, &ngx_posted_events);
    }
}


void
ngx_event_busy_lock_cancel(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx)
{
    ngx_event_busy_lock_ctx_t  *c, *p;

    ngx_mutex_lock(bl->mutex);

    bl->waiting--;

    if (ctx == bl->events) {
        bl->events = ctx->next;

    } else {
        p = bl->events;
        for (c = bl->events->next; c; c = c->next) {
            if (c == ctx) {
                p->next = ctx->next;
                break;
            }
            p = c;
        }
    }

    ngx_mutex_unlock(bl->mutex);
}


static ngx_int_t
ngx_event_busy_lock_look_cacheable(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx)
{
    ngx_int_t    free;
    ngx_uint_t   i, bit, cacheable, mask;

    bit = 0;
    cacheable = 0;
    free = -1;

#if (NGX_SUPPRESS_WARN)
    mask = 0;
#endif

    for (i = 0; i < bl->max_busy; i++) {

        if ((bit & 7) == 0) {
            mask = bl->md5_mask[i / 8];
        }

        if (mask & 1) {
            if (ngx_memcmp(&bl->md5[i * 16], ctx->md5, 16) == 0) {
                ctx->waiting = 1;
                ctx->slot = i;
                return NGX_AGAIN;
            }
            cacheable++;

        } else if (free == -1) {
            free = i;
        }

        if (cacheable == bl->cacheable) {
            if (free == -1 && cacheable < bl->max_busy) {
                free = i + 1;
            }

            break;
        }

        mask >>= 1;
        bit++;
    }

    if (free == -1) {
        return NGX_BUSY;
    }

#if 0
    if (bl->busy == bl->max_busy) {
        return NGX_BUSY;
    }
#endif

    ngx_memcpy(&bl->md5[free * 16], ctx->md5, 16);
    bl->md5_mask[free / 8] |= 1 << (free & 7);
    ctx->slot = free;

    bl->cacheable++;
    bl->busy++;

    return NGX_OK;
}


static void
ngx_event_busy_lock_handler(ngx_event_t *ev)
{
    ev->handler = ngx_event_busy_lock_posted_handler;

    ngx_post_event(ev, &ngx_posted_events);
}


static void
ngx_event_busy_lock_posted_handler(ngx_event_t *ev)
{
    ngx_event_busy_lock_ctx_t  *ctx;

    ctx = ev->data;
    ctx->handler(ev);
}