Messages in this thread | | | Date | Wed, 24 Nov 2010 09:15:57 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 2/4] alloc_contig_pages() find appropriate physical memory range |
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On Mon, 22 Nov 2010 20:20:14 +0900 Minchan Kim <minchan.kim@gmail.com> wrote:
> On Fri, Nov 19, 2010 at 5:14 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@jp.fujitsu.com> wrote: > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > Unlike memory hotplug, at an allocation of contigous memory range, address > > may not be a problem. IOW, if a requester of memory wants to allocate 100M of > > of contigous memory, placement of allocated memory may not be a problem. > > So, "finding a range of memory which seems to be MOVABLE" is required. > > > > This patch adds a functon to isolate a length of memory within [start, end). > > This function returns a pfn which is 1st page of isolated contigous chunk > > of given length within [start, end). > > > > If no_search=true is passed as argument, start address is always same to > > the specified "base" addresss. > > > > After isolation, free memory within this area will never be allocated. > > But some pages will remain as "Used/LRU" pages. They should be dropped by > > page reclaim or migration. > > > > Changelog: 2010-11-17 > > - fixed some conding style (if-then-else) > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > --- > > mm/page_isolation.c | 146 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 146 insertions(+) > > > > Index: mmotm-1117/mm/page_isolation.c > > =================================================================== > > --- mmotm-1117.orig/mm/page_isolation.c > > +++ mmotm-1117/mm/page_isolation.c > > @@ -7,6 +7,7 @@ > > #include <linux/pageblock-flags.h> > > #include <linux/memcontrol.h> > > #include <linux/migrate.h> > > +#include <linux/memory_hotplug.h> > > #include <linux/mm_inline.h> > > #include "internal.h" > > > > @@ -250,3 +251,148 @@ int do_migrate_range(unsigned long start > > out: > > return ret; > > } > > + > > +/* > > + * Functions for getting contiguous MOVABLE pages in a zone. > > + */ > > +struct page_range { > > + unsigned long base; /* Base address of searching contigouous block */ > > + unsigned long end; > > + unsigned long pages;/* Length of contiguous block */ > > Nitpick. > You used nr_pages in other place. > I hope you use the name consistent. > Sure, I'll fix it.
> > + int align_order; > > + unsigned long align_mask; > > Does we really need this field 'align_mask'?
No.
> We can get always from align_order. >
Always writes ((1 << align_order) -1) ? Hmm.
> > +}; > > + > > +int __get_contig_block(unsigned long pfn, unsigned long nr_pages, void *arg) > > +{ > > + struct page_range *blockinfo = arg; > > + unsigned long end; > > + > > + end = pfn + nr_pages; > > + pfn = ALIGN(pfn, 1 << blockinfo->align_order); > > + end = end & ~(MAX_ORDER_NR_PAGES - 1); > > + > > + if (end < pfn) > > + return 0; > > + if (end - pfn >= blockinfo->pages) { > > + blockinfo->base = pfn; > > + blockinfo->end = end; > > + return 1; > > + } > > + return 0; > > +} > > + > > +static void __trim_zone(struct zone *zone, struct page_range *range) > > +{ > > + unsigned long pfn; > > + /* > > + * skip pages which dones'nt under the zone. > > typo dones'nt -> doesn't :) > will fix.
> > + * There are some archs which zones are not in linear layout. > > + */ > > + if (page_zone(pfn_to_page(range->base)) != zone) { > > + for (pfn = range->base; > > + pfn < range->end; > > + pfn += MAX_ORDER_NR_PAGES) { > > + if (page_zone(pfn_to_page(pfn)) == zone) > > + break; > > + } > > + range->base = min(pfn, range->end); > > + } > > + /* Here, range-> base is in the zone if range->base != range->end */ > > + for (pfn = range->base; > > + pfn < range->end; > > + pfn += MAX_ORDER_NR_PAGES) { > > + if (zone != page_zone(pfn_to_page(pfn))) { > > + pfn = pfn - MAX_ORDER_NR_PAGES; > > + break; > > + } > > + } > > + range->end = min(pfn, range->end); > > + return; > > Remove return > Ah, ok.
> > +} > > + > > +/* > > + * This function is for finding a contiguous memory block which has length > > + * of pages and MOVABLE. If it finds, make the range of pages as ISOLATED > > + * and return the first page's pfn. > > + * This checks all pages in the returned range is free of Pg_LRU. To reduce > > + * the risk of false-positive testing, lru_add_drain_all() should be called > > + * before this function to reduce pages on pagevec for zones. > > + */ > > + > > +static unsigned long find_contig_block(unsigned long base, > > + unsigned long end, unsigned long pages, > > + int align_order, struct zone *zone) > > +{ > > + unsigned long pfn, pos; > > + struct page_range blockinfo; > > + int ret; > > + > > + VM_BUG_ON(pages & (MAX_ORDER_NR_PAGES - 1)); > > + VM_BUG_ON(base & ((1 << align_order) - 1)); > > +retry: > > + blockinfo.base = base; > > + blockinfo.end = end; > > + blockinfo.pages = pages; > > + blockinfo.align_order = align_order; > > + blockinfo.align_mask = (1 << align_order) - 1; > > We don't need this. > mask ?
> > + /* > > + * At first, check physical page layout and skip memory holes. > > + */ > > + ret = walk_system_ram_range(base, end - base, &blockinfo, > > + __get_contig_block); > > + if (!ret) > > + return 0; > > + /* check contiguous pages in a zone */ > > + __trim_zone(zone, &blockinfo); > > + > > + /* > > + * Ok, we found contiguous memory chunk of size. Isolate it. > > + * We just search MAX_ORDER aligned range. > > + */ > > + for (pfn = blockinfo.base; pfn + pages <= blockinfo.end; > > + pfn += (1 << align_order)) { > > + struct zone *z = page_zone(pfn_to_page(pfn)); > > + if (z != zone) > > + continue; > > Could we make sure pass __trim_zone is to satisfy whole pfn in zone > what we want. > Repeated the zone check is rather annoying. > I mean let's __get_contig_block or __trim_zone already does check zone > so that we remove the zone check in here.
Ah, yes. I'll remove this.
> > > + > > + spin_lock_irq(&z->lock); > > + pos = pfn; > > + /* > > + * Check the range only contains free pages or LRU pages. > > + */ > > + while (pos < pfn + pages) { > > + struct page *p; > > + > > + if (!pfn_valid_within(pos)) > > + break; > > + p = pfn_to_page(pos); > > + if (PageReserved(p)) > > + break; > > + if (!page_count(p)) { > > + if (!PageBuddy(p)) > > + pos++; > > + else > > + pos += (1 << page_order(p)); > > + } else if (PageLRU(p)) { > > Could we check get_pageblock_migratetype(page) == MIGRATE_MOVABLE in > here and early bail out? >
I'm not sure that's very good. pageblock-type can be fragmented and even if pageblock-type is not MIGRATABLE, all pages in pageblock may be free. Because PageLRU() is checked, all required 'quick' check is done, I think.
> > + pos++; > > + } else > > + break; > > + } > > + spin_unlock_irq(&z->lock); > > + if ((pos == pfn + pages)) { > > + if (!start_isolate_page_range(pfn, pfn + pages)) > > + return pfn; > > + } else/* the chunk including "pos" should be skipped */ > > + pfn = pos & ~((1 << align_order) - 1); > > + cond_resched(); > > + } > > + > > + /* failed */ > > + if (blockinfo.end + pages <= end) { > > + /* Move base address and find the next block of RAM. */ > > + base = blockinfo.end; > > + goto retry; > > + } > > + return 0; > > If the base is 0, isn't it impossible return pfn 0? > x86 in FLAT isn't impossible but I think some architecture might be possible. > Just guessing. > > How about returning negative value and return first page pfn and last > page pfn as out parameter base, end? >
Hmm, will add a check.
Thanks, -Kame
> > +} > > > > > > > > -- > Kind regards, > Minchan Kim > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.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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