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Message-ID: <53CEBCF3.9010208@imgtec.com> Date: Tue, 22 Jul 2014 12:35:15 -0700 From: Leonid Yegoshin <Leonid.Yegoshin@...tec.com> To: Max Filippov <jcmvbkbc@...il.com> CC: <linux-xtensa@...ux-xtensa.org>, Chris Zankel <chris@...kel.net>, "Marc Gauthier" <marc@...ence.com>, <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, <linux-arch@...r.kernel.org>, <linux-mips@...ux-mips.org>, David Rientjes <rientjes@...gle.com> Subject: Re: [PATCH 6/8] mm/highmem: make kmap cache coloring aware On 07/22/2014 12:01 PM, Max Filippov wrote: > From: Leonid Yegoshin <Leonid.Yegoshin@...tec.com> > > Provide hooks that allow architectures with aliasing cache to align > mapping address of high pages according to their color. Such architectures > may enforce similar coloring of low- and high-memory page mappings and > reuse existing cache management functions to support highmem. > > Cc: linux-mm@...ck.org > Cc: linux-arch@...r.kernel.org > Cc: linux-mips@...ux-mips.org > Cc: David Rientjes <rientjes@...gle.com> > Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@...tec.com> > [ Max: extract architecture-independent part of the original patch, clean > up checkpatch and build warnings. ] > Signed-off-by: Max Filippov <jcmvbkbc@...il.com> > --- > Changes since the initial version: > - define set_pkmap_color(pg, cl) as do { } while (0) instead of /* */; > - rename is_no_more_pkmaps to no_more_pkmaps; > - change 'if (count > 0)' to 'if (count)' to better match the original > code behavior; > > mm/highmem.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/mm/highmem.c b/mm/highmem.c > index b32b70c..88fb62e 100644 > --- a/mm/highmem.c > +++ b/mm/highmem.c > @@ -44,6 +44,14 @@ DEFINE_PER_CPU(int, __kmap_atomic_idx); > */ > #ifdef CONFIG_HIGHMEM > > +#ifndef ARCH_PKMAP_COLORING > +#define set_pkmap_color(pg, cl) do { } while (0) > +#define get_last_pkmap_nr(p, cl) (p) > +#define get_next_pkmap_nr(p, cl) (((p) + 1) & LAST_PKMAP_MASK) > +#define no_more_pkmaps(p, cl) (!(p)) > +#define get_next_pkmap_counter(c, cl) ((c) - 1) > +#endif > + > unsigned long totalhigh_pages __read_mostly; > EXPORT_SYMBOL(totalhigh_pages); > > @@ -161,19 +169,24 @@ static inline unsigned long map_new_virtual(struct page *page) > { > unsigned long vaddr; > int count; > + int color __maybe_unused; > + > + set_pkmap_color(page, color); > + last_pkmap_nr = get_last_pkmap_nr(last_pkmap_nr, color); > > start: > count = LAST_PKMAP; > /* Find an empty entry */ > for (;;) { > - last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK; > - if (!last_pkmap_nr) { > + last_pkmap_nr = get_next_pkmap_nr(last_pkmap_nr, color); > + if (no_more_pkmaps(last_pkmap_nr, color)) { > flush_all_zero_pkmaps(); > count = LAST_PKMAP; > } > if (!pkmap_count[last_pkmap_nr]) > break; /* Found a usable entry */ > - if (--count) > + count = get_next_pkmap_counter(count, color); > + if (count) > continue; > > /* I would like to return back to "if (count >0)". The reason is in easy way to jump through the same coloured pages - next element is calculated via decrementing by non "1" value of colours and it can easy become negative on last page available: #define get_next_pkmap_counter(c,cl) (c - FIX_N_COLOURS) where FIX_N_COLOURS is a max number of page colours. Besides that it is a good practice in stopping cycle. - Leonid. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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