Adam Litke [off-list ref] wrote:

This patch attempts to reduce page fault overhead for mmap'd files.  All 
pages in the page cache that will be managed by the current vma are 
instantiated in the page table.  This boots, but some applications fail 
(eg. make).  I am probably missing a corner case somewhere.  Let me know 
what you think.

Well it's simple enough.

I'd like to see it using find_get_pages() though.

And find a way to hold the pte page's atomic kmap across the whole pte page
(or at least a find_get_pages' chunk worth) rather than dropping and
reacquiring it all the time.

Perhaps it can use install_page() as well, rather than open-coding it?

+		pte = pte_offset_map(pmd, address);
+		if(pte_none(*pte)) { /* don't touch instantiated ptes */
+			new_page = find_get_page(mapping, offset);
+			if(!new_page)
+				continue;
+			
+			/* This code taken directly from do_no_page() */
+			pte_chain = pte_chain_alloc(GFP_KERNEL);

Cannot do a sleeping allocation while holding the atomic kmap from
pte_offset_map().  

+			++mm->rss;
+			flush_icache_page(vma, new_page);
+			entry = mk_pte(new_page, vma->vm_page_prot);
+			set_pte(pte, entry);
+			pte_chain = page_add_rmap(new_page, pte, pte_chain);
+			pte_unmap(page_table);
+			update_mmu_cache(vma, address, *pte);
+			pte_chain_free(pte_chain);
+		}

		else
			pte_unmap(pte);



And the pte_chain handling can be optimised:

	struct pte_chain *pte_chain = NULL;

	...
	for ( ... ) {
		if (pte_chain == NULL)
			pte_chain = pte_chain_alloc();
		...
		pte_chain = page_add_rmap(page, pte_chain);
	}
	...
	pte_chain_free(pte_chain);


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"aart@kvack.org"> aart@kvack.org </a>