[PATCH 1 of 2] Buffers reuse in chunked filter

Maxim Dounin mdounin at mdounin.ru
Fri Sep 9 12:42:40 UTC 2011


Hello!

On Fri, Sep 09, 2011 at 02:36:55PM +0200, Kornél Schadl wrote:

> are these patches included in svn?

Not yet.  I need Igor's approval to do so, the patches are posted 
here as a part of review process.

Maxim Dounin

> 
> On Fri, Sep 9, 2011 at 2:01 PM, SplitIce <mat999 at gmail.com> wrote:
> > wow, makes me want to rebuild all my server nodes to include this patch.
> >
> > On Fri, Sep 9, 2011 at 8:32 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:
> >>
> >> # HG changeset patch
> >> # User Maxim Dounin <mdounin at mdounin.ru>
> >> # Date 1315564269 -14400
> >> # Node ID b667ed67c0b9046b94291fa6f52e850006011718
> >> # Parent  014764a85840606c90317e9f44f2b9fa139cbc8b
> >> Buffers reuse in chunked filter.
> >>
> >> There were 2 buffers allocated on each buffer chain sent through chunked
> >> filter (one buffer for chunk size, another one for trailing CRLF, about
> >> 120 bytes in total on 32-bit platforms).  This resulted in large memory
> >> consumption with long-lived requests sending many buffer chains.  Usual
> >> example of problematic scenario is streaming though proxy with
> >> proxy_buffering set to off.
> >>
> >> Introduced buffers reuse reduces memory consumption in the above
> >> problematic
> >> scenario.
> >>
> >> See here for initial report:
> >> http://mailman.nginx.org/pipermail/nginx/2010-April/019814.html
> >>
> >> diff --git a/src/http/modules/ngx_http_chunked_filter_module.c
> >> b/src/http/modules/ngx_http_chunked_filter_module.c
> >> --- a/src/http/modules/ngx_http_chunked_filter_module.c
> >> +++ b/src/http/modules/ngx_http_chunked_filter_module.c
> >> @@ -9,6 +9,12 @@
> >>  #include <ngx_http.h>
> >>
> >>
> >> +typedef struct {
> >> +    ngx_chain_t         *free;
> >> +    ngx_chain_t         *busy;
> >> +} ngx_http_chunked_filter_ctx_t;
> >> +
> >> +
> >>  static ngx_int_t ngx_http_chunked_filter_init(ngx_conf_t *cf);
> >>
> >>
> >> @@ -50,7 +56,8 @@ static ngx_http_output_body_filter_pt
> >>  static ngx_int_t
> >>  ngx_http_chunked_header_filter(ngx_http_request_t *r)
> >>  {
> >> -    ngx_http_core_loc_conf_t  *clcf;
> >> +    ngx_http_core_loc_conf_t       *clcf;
> >> +    ngx_http_chunked_filter_ctx_t  *ctx;
> >>
> >>     if (r->headers_out.status == NGX_HTTP_NOT_MODIFIED
> >>         || r->headers_out.status == NGX_HTTP_NO_CONTENT
> >> @@ -70,6 +77,14 @@ ngx_http_chunked_header_filter(ngx_http_
> >>             if (clcf->chunked_transfer_encoding) {
> >>                 r->chunked = 1;
> >>
> >> +                ctx = ngx_pcalloc(r->pool,
> >> +                                  sizeof(ngx_http_chunked_filter_ctx_t));
> >> +                if (ctx == NULL) {
> >> +                    return NGX_ERROR;
> >> +                }
> >> +
> >> +                ngx_http_set_ctx(r, ctx, ngx_http_chunked_filter_module);
> >> +
> >>             } else {
> >>                 r->keepalive = 0;
> >>             }
> >> @@ -83,17 +98,21 @@ ngx_http_chunked_header_filter(ngx_http_
> >>  static ngx_int_t
> >>  ngx_http_chunked_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
> >>  {
> >> -    u_char       *chunk;
> >> -    off_t         size;
> >> -    ngx_buf_t    *b;
> >> -    ngx_chain_t   out, tail, *cl, *tl, **ll;
> >> +    u_char                         *chunk;
> >> +    off_t                           size;
> >> +    ngx_int_t                       rc;
> >> +    ngx_buf_t                      *b;
> >> +    ngx_chain_t                    *out, *cl, *tl, **ll;
> >> +    ngx_http_chunked_filter_ctx_t  *ctx;
> >>
> >>     if (in == NULL || !r->chunked || r->header_only) {
> >>         return ngx_http_next_body_filter(r, in);
> >>     }
> >>
> >> -    out.buf = NULL;
> >> -    ll = &out.next;
> >> +    ctx = ngx_http_get_module_ctx(r, ngx_http_chunked_filter_module);
> >> +
> >> +    out = NULL;
> >> +    ll = &out;
> >>
> >>     size = 0;
> >>     cl = in;
> >> @@ -127,31 +146,46 @@ ngx_http_chunked_body_filter(ngx_http_re
> >>     }
> >>
> >>     if (size) {
> >> -        b = ngx_calloc_buf(r->pool);
> >> -        if (b == NULL) {
> >> +        tl = ngx_chain_get_free_buf(r->pool, &ctx->free);
> >> +        if (tl == NULL) {
> >>             return NGX_ERROR;
> >>         }
> >>
> >> -        /* the "0000000000000000" is 64-bit hexadimal string */
> >> +        b = tl->buf;
> >> +        chunk = b->start;
> >>
> >> -        chunk = ngx_palloc(r->pool, sizeof("0000000000000000" CRLF) - 1);
> >>         if (chunk == NULL) {
> >> -            return NGX_ERROR;
> >> +            /* the "0000000000000000" is 64-bit hexadecimal string */
> >> +
> >> +            chunk = ngx_palloc(r->pool, sizeof("0000000000000000" CRLF) -
> >> 1);
> >> +            if (chunk == NULL) {
> >> +                return NGX_ERROR;
> >> +            }
> >> +
> >> +            b->start = chunk;
> >> +            b->end = chunk + sizeof("0000000000000000" CRLF) - 1;
> >>         }
> >>
> >> +        b->tag = (ngx_buf_tag_t) &ngx_http_chunked_filter_module;
> >> +        b->memory = 0;
> >>         b->temporary = 1;
> >>         b->pos = chunk;
> >>         b->last = ngx_sprintf(chunk, "%xO" CRLF, size);
> >>
> >> -        out.buf = b;
> >> +        tl->next = out;
> >> +        out = tl;
> >>     }
> >>
> >>     if (cl->buf->last_buf) {
> >> -        b = ngx_calloc_buf(r->pool);
> >> -        if (b == NULL) {
> >> +        tl = ngx_chain_get_free_buf(r->pool, &ctx->free);
> >> +        if (tl == NULL) {
> >>             return NGX_ERROR;
> >>         }
> >> +
> >> +        b = tl->buf;
> >>
> >> +        b->tag = (ngx_buf_tag_t) &ngx_http_chunked_filter_module;
> >> +        b->temporary = 0;
> >>         b->memory = 1;
> >>         b->last_buf = 1;
> >>         b->pos = (u_char *) CRLF "0" CRLF CRLF;
> >> @@ -159,35 +193,38 @@ ngx_http_chunked_body_filter(ngx_http_re
> >>
> >>         cl->buf->last_buf = 0;
> >>
> >> +        *ll = tl;
> >> +
> >>         if (size == 0) {
> >>             b->pos += 2;
> >> -            out.buf = b;
> >> -            out.next = NULL;
> >> -
> >> -            return ngx_http_next_body_filter(r, &out);
> >>         }
> >>
> >> -    } else {
> >> -        if (size == 0) {
> >> -            *ll = NULL;
> >> -            return ngx_http_next_body_filter(r, out.next);
> >> -        }
> >> -
> >> -        b = ngx_calloc_buf(r->pool);
> >> -        if (b == NULL) {
> >> +    } else if (size > 0) {
> >> +        tl = ngx_chain_get_free_buf(r->pool, &ctx->free);
> >> +        if (tl == NULL) {
> >>             return NGX_ERROR;
> >>         }
> >>
> >> +        b = tl->buf;
> >> +
> >> +        b->tag = (ngx_buf_tag_t) &ngx_http_chunked_filter_module;
> >> +        b->temporary = 0;
> >>         b->memory = 1;
> >>         b->pos = (u_char *) CRLF;
> >>         b->last = b->pos + 2;
> >> +
> >> +        *ll = tl;
> >> +
> >> +    } else {
> >> +        *ll = NULL;
> >>     }
> >>
> >> -    tail.buf = b;
> >> -    tail.next = NULL;
> >> -    *ll = &tail;
> >> +    rc = ngx_http_next_body_filter(r, out);
> >>
> >> -    return ngx_http_next_body_filter(r, &out);
> >> +    ngx_chain_update_chains(&ctx->free, &ctx->busy, &out,
> >> +                            (ngx_buf_tag_t)
> >> &ngx_http_chunked_filter_module);
> >> +
> >> +    return rc;
> >>  }
> >>
> >>
> >>
> >> _______________________________________________
> >> nginx-devel mailing list
> >> nginx-devel at nginx.org
> >> http://mailman.nginx.org/mailman/listinfo/nginx-devel
> >
> >
> > _______________________________________________
> > nginx-devel mailing list
> > nginx-devel at nginx.org
> > http://mailman.nginx.org/mailman/listinfo/nginx-devel
> >
> 
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