From: "Weiny, Ira" <ira.weiny@intel.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: RE: [PATCH 02/11] mm: Pass order to __alloc_pages_nodemask in GFP flags
Date: Thu, 9 May 2019 16:22:33 +0000 [thread overview]
Message-ID: <2807E5FD2F6FDA4886F6618EAC48510E79D0CEBC@CRSMSX101.amr.corp.intel.com> (raw)
In-Reply-To: <20190509135816.GA23561@bombadil.infradead.org>
>
> On Wed, May 08, 2019 at 06:50:16PM -0700, Ira Weiny wrote:
> > On Mon, May 06, 2019 at 09:06:00PM -0700, Matthew Wilcox wrote:
> > > Save marshalling an extra argument in all the callers at the expense
> > > of using five bits of the GFP flags. We still have three GFP bits
> > > remaining after doing this (and we can release one more by
> > > reallocating NORETRY, RETRY_MAYFAIL and NOFAIL).
>
> > > -static void *dsalloc_pages(size_t size, gfp_t flags, int cpu)
> > > +static void *dsalloc_pages(size_t size, gfp_t gfp, int cpu)
> > > {
> > > unsigned int order = get_order(size);
> > > int node = cpu_to_node(cpu);
> > > struct page *page;
> > >
> > > - page = __alloc_pages_node(node, flags | __GFP_ZERO, order);
> > > + page = __alloc_pages_node(node, gfp | __GFP_ZERO |
> > > +__GFP_ORDER(order));
> >
> > Order was derived from size in this function. Is this truely equal to
> > the old function?
> >
> > At a minimum if I am wrong the get_order call above should be removed,
> no?
>
> I think you have a misunderstanding, but I'm not sure what it is.
>
> Before this patch, we pass 'order' (a small integer generally less than 10) in
> the bottom few bits of a parameter called 'order'. After this patch, we pass
> the order in some of the high bits of the GFP flags. So we can't remove the
> call to get_order() because that's what calculates 'order' from 'size'.
Ah I see it now. Sorry was thinking the wrong thing when I saw that line.
Yep you are correct,
Ira
>
> > > +#define __GFP_ORDER(order) ((__force gfp_t)(order <<
> __GFP_BITS_SHIFT))
> > > +#define __GFP_ORDER_PMD __GFP_ORDER(PMD_SHIFT -
> PAGE_SHIFT)
> > > +#define __GFP_ORDER_PUD __GFP_ORDER(PUD_SHIFT -
> PAGE_SHIFT)
> > > +
> > > +/*
> > > + * Extract the order from a GFP bitmask.
> > > + * Must be the top bits to avoid an AND operation. Don't let
> > > + * __GFP_BITS_SHIFT get over 27, or we won't be able to encode
> > > +orders
> > > + * above 15 (some architectures allow configuring MAX_ORDER up to
> > > +64,
> > > + * but I doubt larger than 31 are ever used).
> > > + */
> > > +#define gfp_order(gfp) (((__force unsigned int)gfp) >>
> __GFP_BITS_SHIFT)
next prev parent reply other threads:[~2019-05-09 16:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-07 4:05 [RFC 00/11] Remove 'order' argument from many mm functions Matthew Wilcox
2019-05-07 4:05 ` [PATCH 01/11] fix function alignment Matthew Wilcox
2019-05-09 10:55 ` Kirill A. Shutemov
2019-05-07 4:06 ` [PATCH 02/11] mm: Pass order to __alloc_pages_nodemask in GFP flags Matthew Wilcox
2019-05-09 1:50 ` Ira Weiny
2019-05-09 13:58 ` Matthew Wilcox
2019-05-09 16:22 ` Weiny, Ira [this message]
2019-05-09 10:59 ` Kirill A. Shutemov
2019-05-07 4:06 ` [PATCH 03/11] mm: Pass order to __get_free_pages() " Matthew Wilcox
2019-05-07 4:06 ` [PATCH 04/11] mm: Pass order to prep_new_page " Matthew Wilcox
2019-05-07 4:06 ` [PATCH 05/11] mm: Remove gfp_flags argument from rmqueue_pcplist Matthew Wilcox
2019-05-07 4:06 ` [PATCH 06/11] mm: Pass order to rmqueue in GFP flags Matthew Wilcox
2019-05-07 4:06 ` [PATCH 07/11] mm: Pass order to get_page_from_freelist " Matthew Wilcox
2019-05-07 4:06 ` [PATCH 08/11] mm: Pass order to __alloc_pages_cpuset_fallback " Matthew Wilcox
2019-05-07 4:06 ` [PATCH 09/11] mm: Pass order to prepare_alloc_pages " Matthew Wilcox
2019-05-07 4:06 ` [PATCH 10/11] mm: Pass order to try_to_free_pages " Matthew Wilcox
2019-05-07 4:06 ` [PATCH 11/11] mm: Pass order to node_reclaim() " Matthew Wilcox
2019-05-09 1:58 ` [RFC 00/11] Remove 'order' argument from many mm functions Ira Weiny
2019-05-09 14:07 ` Matthew Wilcox
2019-05-09 16:48 ` Weiny, Ira
2019-05-09 18:29 ` Matthew Wilcox
2019-05-29 21:44 ` Ira Weiny
2019-05-09 11:07 ` Kirill A. Shutemov
2019-05-14 14:51 ` Matthew Wilcox
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