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Message-ID: <53CDBB01.7040007@imgtec.com> Date: Mon, 21 Jul 2014 18:14:41 -0700 From: Leonid Yegoshin <Leonid.Yegoshin@...tec.com> To: David Rientjes <rientjes@...gle.com> CC: Max Filippov <jcmvbkbc@...il.com>, <linux-mm@...ck.org>, <linux-arch@...r.kernel.org>, <linux-mips@...ux-mips.org>, <linux-xtensa@...ux-xtensa.org>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2] mm/highmem: make kmap cache coloring aware On 07/21/2014 05:58 PM, David Rientjes wrote: > On Thu, 17 Jul 2014, 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. >> > Typically a change like this would be proposed along with a change to an > architecture which would define this new ARCH_PKMAP_COLORING and have its > own overriding definitions. Based on who you sent this patch to, it looks > like that would be mips and xtensa. Now the only question is where are > those patches to add the alternate definitions for those platforms? Yes, there is one, at least for MIPS. This stuff can be a common ground for both platforms (MIPS and XTENSA) > >> 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 v1->v2: >> - fix description >> >> mm/highmem.c | 19 ++++++++++++++++--- >> 1 file changed, 16 insertions(+), 3 deletions(-) >> >> diff --git a/mm/highmem.c b/mm/highmem.c >> index b32b70c..6898a8b 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) /* */ > This is typically done with do {} while (0). > >> +#define get_last_pkmap_nr(p, cl) (p) >> +#define get_next_pkmap_nr(p, cl) (((p) + 1) & LAST_PKMAP_MASK) >> +#define is_no_more_pkmaps(p, cl) (!(p)) > That's not gramatically proper. > >> +#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 (is_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); > And that's not equivalent at all, --count decrements the auto variable and > then tests it for being non-zero. Your get_next_pkmap_counter() never > decrements count. David, the statements count = get_next_pkmap_counter(count, color); if (count > 0) are extended in STANDARD (non colored) case to count = (count - 1); if (count > 0) which are perfect equivalent of if (--count) > >> + if (count > 0) >> continue; >> >> /* -- 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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