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SubjectRE: [patch] hugetlb strict commit accounting
Date
Chen, Kenneth W wrote on Thursday, March 09, 2006 4:02 AM
> David Gibson wrote on Thursday, March 09, 2006 3:27 AM
> > Again, there are no changes to the fault handler. Including the
> > promised changes which would mean my instantiation serialization path
> > isn't necessary ;-).
>
> This is the major portion that I omitted in the first patch and is the
> real kicker that fulfills the promise of guaranteed available hugetlb
> page for shared mapping.

Take a look at the following snippets of earlier patch: in
hugetlb_reserve_pages(), region_chg() calculates an estimate how many
pages is needed, then calls to hugetlb_acct_memory() to make sure there
are enough pages available, then another call to region_add to confirm
the reservation. It looks OK to me.


+int hugetlb_acct_memory(long delta)
+{
+ atomic_add(delta, &resv_huge_pages);
+ if (delta > 0 && atomic_read(&resv_huge_pages) >
+ VMACCTPG(hugetlb_total_pages())) {
+ atomic_add(-delta, &resv_huge_pages);
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+static int hugetlb_reserve_pages(struct inode *inode, int from, int to)
+{
+ int ret, chg;
+
+ chg = region_chg(&inode->i_mapping->private_list, from, to);
+ if (chg < 0)
+ return chg;
+ ret = hugetlb_acct_memory(chg);
+ if (ret < 0)
+ return ret;
+ region_add(&inode->i_mapping->private_list, from, to);
+ return 0;
}


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