[nginx] Bigger iovec buffer in ngx_readv_chain().

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/d1bde5c3c5d2
branches:  
changeset: 5776:d1bde5c3c5d2
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon Jul 28 18:30:19 2014 +0400
description:
Bigger iovec buffer in ngx_readv_chain().

This helps to reduce likelyhood of memory allocations in ngx_readv_chain(),
which are known to lead to noticeable effects in some cases, see
http://mailman.nginx.org/pipermail/nginx/2014-July/044512.html.

diffstat:

 src/os/unix/ngx_readv_chain.c |  6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diffs (16 lines):

diff --git a/src/os/unix/ngx_readv_chain.c b/src/os/unix/ngx_readv_chain.c
--- a/src/os/unix/ngx_readv_chain.c
+++ b/src/os/unix/ngx_readv_chain.c
@@ -10,7 +10,11 @@
 #include <ngx_event.h>
 
 
-#define NGX_IOVS  16
+#if (IOV_MAX > 64)
+#define NGX_IOVS  64
+#else
+#define NGX_IOVS  IOV_MAX
+#endif
 
 
 #if (NGX_HAVE_KQUEUE)