From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by uproxy.gmail.com with SMTP id s2so692827uge for ; Tue, 21 Mar 2006 07:53:40 -0800 (PST) Message-ID: Date: Tue, 21 Mar 2006 10:53:40 -0500 From: "Stone Wang" Subject: Re: [PATCH][8/8] mm: lru interface change In-Reply-To: <441FF007.6020901@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: inline References: <441FF007.6020901@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: > I may have missed something very trivial, but... why are they on a > list at all if they don't get scanned Get the locked pages on a list is necessary for page management, scatter the locked pages around isnt a good idea. Also, we could add some kinds of scan to the locked pages, if we find that it's necessary. Shaoping Wang 2006/3/21, Nick Piggin : > Stone Wang wrote: > > Add Wired list to LRU. > > Add PG_Wired bit to page. > > > > I may have missed something very trivial, but... why are they on a > list at all if they don't get scanned? > > > > diff -urN linux-2.6.15.orig/mm/swap.c linux-2.6.15/mm/swap.c > > --- linux-2.6.15.orig/mm/swap.c 2006-01-02 22:21:10.000000000 -0500 > > +++ linux-2.6.15/mm/swap.c 2006-03-07 11:45:37.000000000 -0500 > > @@ -110,6 +110,44 @@ > > spin_unlock_irq(&zone->lru_lock); > > } > > > > +/* Wire the page; if the page is in LRU, > > + * try move it to Wired list. > > + */ > > +void fastcall wire_page(struct page *page) > > Ahh, here's the elusive beast. > > > +{ > > + struct zone *zone = page_zone(page); > > + > > + spin_lock_irq(&zone->lru_lock); > > This is a fairly heavy lock for something which is going into page fault > fastpaths and such. You might be better off making wired_count atomic and > not using a lock in the common case if possible (even if it is only for > mlocked pages, I'm sure someone will complain). > > > + page->wired_count ++; > > Oh dear, I missed this change you made to struct page, tucked away in 5/8. > This alone pretty much makes it a showstopper, I'm afraid. You'll have to > work out some other way to do it so as not to penalise 99.999% of machines > which don't need this. > > (Oh, and making the field a short usually won't help either, because of > alignment constraints). > > > + if(!PageWired(page)){ > > + if(PageLRU(page)){ > > + del_page_from_lru(zone, page); > > + add_page_to_wired_list(zone,page); > > + SetPageWired(page); > > + } > > + } > > + spin_unlock_irq(&zone->lru_lock); > > +} > > + > > +/* Unwire the page. > > + * If it isnt wired by any process, try move it to active list. > > + */ > > +void fastcall unwire_page(struct page *page) > > +{ > > + struct zone *zone = page_zone(page); > > + > > + spin_lock_irq(&zone->lru_lock); > > + page->wired_count --; > > + if(!page->wired_count){ > > + if(PageLRU(page) && TestClearPageWired(page)){ > > + del_page_from_wired_list(zone,page); > > + add_page_to_active_list(zone,page); > > + SetPageActive(page); > > + } > > + } > > + spin_unlock_irq(&zone->lru_lock); > > +} > > + > > /* > > * Mark a page as having seen activity. > > * > > @@ -119,11 +157,13 @@ > > */ > > void fastcall mark_page_accessed(struct page *page) > > { > > - if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) { > > - activate_page(page); > > - ClearPageReferenced(page); > > - } else if (!PageReferenced(page)) { > > - SetPageReferenced(page); > > + if(!PageWired(page)) { > > + if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) { > > + activate_page(page); > > + ClearPageReferenced(page); > > + } else if (!PageReferenced(page)) { > > + SetPageReferenced(page); > > + } > > } > > } > > > > So, umm... what happens when the page gets wired before activate_page()? > > > @@ -178,13 +218,15 @@ > > struct zone *zone = page_zone(page); > > > > spin_lock_irqsave(&zone->lru_lock, flags); > > - if (TestClearPageLRU(page)) > > - del_page_from_lru(zone, page); > > - if (page_count(page) != 0) > > - page = NULL; > > + if(!PageWired(page)) { > > + if (TestClearPageLRU(page)) > > + del_page_from_lru(zone, page); > > + if (page_count(page) != 0) > > + page = NULL; > > + if (page) > > + free_hot_page(page); > > + } > > spin_unlock_irqrestore(&zone->lru_lock, flags); > > - if (page) > > - free_hot_page(page); > > } > > > > Hmm... how do PageWired pages get freed, then? > > > EXPORT_SYMBOL(__page_cache_release); > > @@ -214,7 +256,8 @@ > > > > if (!put_page_testzero(page)) > > continue; > > - > > + if(PageWired(page)) > > + continue; > > pagezone = page_zone(page); > > if (pagezone != zone) { > > if (zone) > > Ditto. > > -- > SUSE Labs, Novell Inc. > > > Send instant messages to your online friends http://au.messenger.yahoo.com > > -- 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: email@kvack.org