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@mdounin.ru> wrote:

> # HG changeset patch
> # User Maxim Dounin <mdounin@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;
> }
>
>
>
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