[PATCH] Core: bugfix for the ngx_slab_max_size case

[Jianjun Zheng]

:)


2014-07-10 2:40 GMT+08:00 Maxim Dounin <mdounin at mdounin.ru>:

> Hello!
>
> On Wed, Jun 18, 2014 at 05:00:14PM +0800, Jianjun Zheng wrote:
>
> > At present, alloting memory with size of ngx_slab_max_size causes
> >
> > 1) an internal fragmentation, size of ngx_slab_max_size, comes into being
> >
> > 2) the slot with index of (ngx_pagesize_shift - pool->min_shift - 1)
> >     is the right slot for this size.
> >
> >
> > # HG changeset patch
> > # User Jianjun Zheng <codeeply at gmail.com>
> > # Date 1403080799 -28800
> > #      Wed Jun 18 16:39:59 2014 +0800
> > # Node ID 1704335dd810e2e2abb2b393b4f7b7c9004c6012
> > # Parent  ec919574cc14f7781c0ca212cffec586f88eec40
> > Core: bugfix for the ngx_slab_max_size case
> >
> > diff -r ec919574cc14 -r 1704335dd810 src/core/ngx_slab.c
> > --- a/src/core/ngx_slab.c Tue Jun 17 16:51:25 2014 +0400
> > +++ b/src/core/ngx_slab.c Wed Jun 18 16:39:59 2014 +0800
> > @@ -160,7 +160,7 @@
> >      ngx_uint_t        i, slot, shift, map;
> >      ngx_slab_page_t  *page, *prev, *slots;
> >
> > -    if (size >= ngx_slab_max_size) {
> > +    if (size > ngx_slab_max_size) {
> >
> >          ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, ngx_cycle->log, 0,
> >                         "slab alloc: %uz", size);
>
> Sorry for late reply.
>
> Yes, the patch is right, allocation of ngx_slab_max_size exactly
> (aka half page, 2048 bytes on platforms with 4k pages) can be
> satisfied from the largest slot and don't need the whole page to
> be allocated.  While it's a corner case, it's certainly can be
> important in some cases and worth fixing.
>
> Committed, thanks.
>
> --
> Maxim Dounin
> http://nginx.org/
>
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>
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