On Mon, Apr 15, 2024 at 01:10:53PM -0700, Andrew Morton wrote:
> On Mon, 15 Apr 2024 09:21:36 +0800 Long Li <leo.lilong@xxxxxxxxxx> wrote:
>
> > The commit 63b1898fffcd ("XArray: Disallow sibling entries of nodes")
> > modified the xas_descend function in such a way that it was no longer
> > being compiled as an inline function, because it increased the size of
> > xas_descend(), and the compiler no longer optimizes it as inline. This
> > had a negative impact on performance, xas_descend is called frequently
> > to traverse downwards in the xarray tree, making it a hot function.
> >
> > Inlining xas_descend has been shown to significantly improve performance
> > by approximately 4.95% in the iozone write test.
> >
> > Machine: Intel(R) Xeon(R) Gold 6240 CPU @ 2.60GHz
> > #iozone i 0 -i 1 -s 64g -r 16m -f /test/tmptest
> >
> > Before this patch:
> >
> > kB reclen write rewrite read reread
> > 67108864 16384 2230080 3637689 6 315197 5496027
> >
> > After this patch:
> >
> > kB reclen write rewrite read reread
> > 67108864 16384 2340360 3666175 6272401 5460782
> >
> > Percentage change:
> > 4.95% 0.78% -0.68% -0.64%
> >
> > This patch introduces inlining to the xas_descend function. While this
> > change increases the size of lib/xarray.o, the performance gains in
> > critical workloads make this an acceptable trade-off.
> >
> > Size comparison before and after patch:
> > .text .data .bss file
> > 0x3502 0 0 lib/xarray.o.before
> > 0x3602 0 0 lib/xarray.o.after
> >
> > ...
> >
> > --- a/lib/xarray.c
> > +++ b/lib/xarray.c
> > @@ -200,7 +200,7 @@ static void *xas_start(struct xa_state *xas)
> > return entry;
> > }
> >
> > -static void *xas_descend(struct xa_state *xas, struct xa_node *node)
> > +static inline void *xas_descend(struct xa_state *xas, struct xa_node *node)
> > {
> > unsigned int offset = get_offset(xas->xa_index, node);
> > void *entry = xa_entry(xas->xa, node, offset);
>
> I thought gcc nowadays treats `inline' as avisory and still makes up
> its own mind?
>
> Perhaps we should use __always_inline here?
Yes, I agree with you, I will send a new version. thanks!
