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---------- Forwarded message ----------
Date: Tue, 24 Apr 2001 23:28:38 -0300 (BRT)
From: Marcelo Tosatti <marcelo@conectiva.com.br>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Ingo Molnar <mingo@elte.hu>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
Linux Kernel List <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
Rik van Riel <riel@conectiva.com.br>,
Szabolcs Szakacsits <szaka@f-secure.com>
Subject: Re: [patch] swap-speedup-2.4.3-B3
On Tue, 24 Apr 2001, Linus Torvalds wrote:
> Basically, I don't want to mix synchronous and asynchronous
> interfaces. Everything should be asynchronous by default, and waiting
> should be explicit.
The following patch changes all swap IO functions to be asynchronous by
default and changes the callers to wait when needed (except
rw_swap_page_base which will block writers if there are too many in flight
swap IOs).
Ingo's find_get_swapcache_page() does not wait on locked pages anymore,
which is now up to the callers.
time make -j32 test with 4 CPUs machine, 128M ram and 128M swap:
pre5
---- 228.04user 28.14system 5:16.52elapsed 80%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (525113major+678617minor)pagefaults 0swapspre5 + attached patch -------------------- 227.18user 25.49system 3:40.53elapsed 114%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (495387major+644924minor)pagefaults 0swaps
Comments?
diff -Nur linux.orig/include/linux/pagemap.h linux/include/linux/pagemap.h --- linux.orig/include/linux/pagemap.h Wed Apr 25 00:51:36 2001 +++ linux/include/linux/pagemap.h Wed Apr 25 00:53:04 2001 @@ -77,7 +77,12 @@ unsigned long index, struct page **hash); extern void lock_page(struct page *page); #define find_lock_page(mapping, index) \ - __find_lock_page(mapping, index, page_hash(mapping, index)) + __find_lock_page(mapping, index, page_hash(mapping, index)) + +extern struct page * __find_get_swapcache_page (struct address_space * mapping, + unsigned long index, struct page **hash); +#define find_get_swapcache_page(mapping, index) \ + __find_get_swapcache_page(mapping, index, page_hash(mapping, index)) extern void __add_page_to_hash_queue(struct page * page, struct page **p); diff -Nur linux.orig/include/linux/swap.h linux/include/linux/swap.h --- linux.orig/include/linux/swap.h Wed Apr 25 00:51:36 2001 +++ linux/include/linux/swap.h Wed Apr 25 00:53:04 2001 @@ -111,8 +111,8 @@ extern int try_to_free_pages(unsigned int gfp_mask); /* linux/mm/page_io.c */ -extern void rw_swap_page(int, struct page *, int); -extern void rw_swap_page_nolock(int, swp_entry_t, char *, int); +extern void rw_swap_page(int, struct page *); +extern void rw_swap_page_nolock(int, swp_entry_t, char *); /* linux/mm/page_alloc.c */ @@ -121,8 +121,7 @@ extern void add_to_swap_cache(struct page *, swp_entry_t); extern int swap_check_entry(unsigned long); extern struct page * lookup_swap_cache(swp_entry_t); -extern struct page * read_swap_cache_async(swp_entry_t, int); -#define read_swap_cache(entry) read_swap_cache_async(entry, 1); +extern struct page * read_swap_cache_async(swp_entry_t); /* linux/mm/oom_kill.c */ extern int out_of_memory(void); diff -Nur linux.orig/mm/filemap.c linux/mm/filemap.c --- linux.orig/mm/filemap.c Wed Apr 25 00:51:35 2001 +++ linux/mm/filemap.c Wed Apr 25 00:53:04 2001 @@ -678,6 +678,34 @@ } /* + * Find a swapcache page (and get a reference) or return NULL. + * The SwapCache check is protected by the pagecache lock. + */ +struct page * __find_get_swapcache_page(struct address_space *mapping, + unsigned long offset, struct page **hash) +{ + struct page *page; + + /* + * We need the LRU lock to protect against page_launder(). + */ + + spin_lock(&pagecache_lock); + page = __find_page_nolock(mapping, offset, *hash); + if (page) { + spin_lock(&pagemap_lru_lock); + if (PageSwapCache(page)) + page_cache_get(page); + else + page = NULL; + spin_unlock(&pagemap_lru_lock); + } + spin_unlock(&pagecache_lock); + + return page; +} + +/* * Same as the above, but lock the page too, verifying that * it's still valid once we own it. */ diff -Nur linux.orig/mm/memory.c linux/mm/memory.c --- linux.orig/mm/memory.c Wed Apr 25 00:51:35 2001 +++ linux/mm/memory.c Wed Apr 25 00:53:04 2001 @@ -1040,7 +1040,7 @@ break; } /* Ok, do the async read-ahead now */ - new_page = read_swap_cache_async(SWP_ENTRY(SWP_TYPE(entry), offset), 0); + new_page = read_swap_cache_async(SWP_ENTRY(SWP_TYPE(entry), offset)); if (new_page != NULL) page_cache_release(new_page); swap_free(SWP_ENTRY(SWP_TYPE(entry), offset)); @@ -1063,13 +1063,13 @@ if (!page) { lock_kernel(); swapin_readahead(entry); - page = read_swap_cache(entry); + page = read_swap_cache_async(entry); unlock_kernel(); if (!page) { spin_lock(&mm->page_table_lock); return -1; } - + wait_on_page(page); flush_page_to_ram(page); flush_icache_page(vma, page); } diff -Nur linux.orig/mm/page_io.c linux/mm/page_io.c --- linux.orig/mm/page_io.c Wed Apr 25 00:51:35 2001 +++ linux/mm/page_io.c Wed Apr 25 00:53:04 2001 @@ -33,7 +33,7 @@ * that shared pages stay shared while being swapped. */ -static int rw_swap_page_base(int rw, swp_entry_t entry, struct page *page, int wait) +static int rw_swap_page_base(int rw, swp_entry_t entry, struct page *page) { unsigned long offset; int zones[PAGE_SIZE/512]; @@ -41,6 +41,7 @@ kdev_t dev = 0; int block_size; struct inode *swapf = 0; + int wait = 0; /* Don't allow too many pending pages in flight.. */ if ((rw == WRITE) && atomic_read(&nr_async_pages) > @@ -104,7 +105,7 @@ * - it's marked as being swap-cache * - it's associated with the swap inode */ -void rw_swap_page(int rw, struct page *page, int wait) +void rw_swap_page(int rw, struct page *page) { swp_entry_t entry; @@ -116,7 +117,7 @@ PAGE_BUG(page); if (page->mapping != &swapper_space) PAGE_BUG(page); - if (!rw_swap_page_base(rw, entry, page, wait)) + if (!rw_swap_page_base(rw, entry, page)) UnlockPage(page); } @@ -125,7 +126,7 @@ * Therefore we can't use it. Later when we can remove the need for the * lock map and we can reduce the number of functions exported. */ -void rw_swap_page_nolock(int rw, swp_entry_t entry, char *buf, int wait) +void rw_swap_page_nolock(int rw, swp_entry_t entry, char *buf) { struct page *page = virt_to_page(buf); @@ -137,7 +138,8 @@ PAGE_BUG(page); /* needs sync_page to wait I/O completation */ page->mapping = &swapper_space; - if (!rw_swap_page_base(rw, entry, page, wait)) + if (!rw_swap_page_base(rw, entry, page)) UnlockPage(page); + wait_on_page(page); page->mapping = NULL; } diff -Nur linux.orig/mm/shmem.c linux/mm/shmem.c --- linux.orig/mm/shmem.c Wed Apr 25 00:51:35 2001 +++ linux/mm/shmem.c Wed Apr 25 00:53:04 2001 @@ -124,6 +124,7 @@ *ptr = (swp_entry_t){0}; freed++; if ((page = lookup_swap_cache(entry)) != NULL) { + wait_on_page(page); delete_from_swap_cache(page); page_cache_release(page); } @@ -329,10 +330,11 @@ spin_unlock (&info->lock); lock_kernel(); swapin_readahead(*entry); - page = read_swap_cache(*entry); + page = read_swap_cache_async(*entry); unlock_kernel(); if (!page) return ERR_PTR(-ENOMEM); + wait_on_page(page); if (!Page_Uptodate(page)) { page_cache_release(page); return ERR_PTR(-EIO); diff -Nur linux.orig/mm/swap_state.c linux/mm/swap_state.c --- linux.orig/mm/swap_state.c Wed Apr 25 00:51:35 2001 +++ linux/mm/swap_state.c Wed Apr 25 00:53:04 2001 @@ -34,7 +34,7 @@ return 0; in_use: - rw_swap_page(WRITE, page, 0); + rw_swap_page(WRITE, page); return 0; } @@ -163,37 +163,18 @@ /* * Right now the pagecache is 32-bit only. But it's a 32 bit index. =) */ -repeat: - found = find_lock_page(&swapper_space, entry.val); + found = find_get_swapcache_page(&swapper_space, entry.val); if (!found) return 0; - /* - * Though the "found" page was in the swap cache an instant - * earlier, it might have been removed by refill_inactive etc. - * Re search ... Since find_lock_page grabs a reference on - * the page, it can not be reused for anything else, namely - * it can not be associated with another swaphandle, so it - * is enough to check whether the page is still in the scache. - */ - if (!PageSwapCache(found)) { - UnlockPage(found); - page_cache_release(found); - goto repeat; - } + if (!PageSwapCache(found)) + BUG(); if (found->mapping != &swapper_space) - goto out_bad; + BUG(); #ifdef SWAP_CACHE_INFO swap_cache_find_success++; #endif - UnlockPage(found); return found; } - -out_bad: - printk (KERN_ERR "VM: Found a non-swapper swap page!\n"); - UnlockPage(found); - page_cache_release(found); - return 0; } /* @@ -205,7 +186,7 @@ * the swap entry is no longer in use. */ -struct page * read_swap_cache_async(swp_entry_t entry, int wait) +struct page * read_swap_cache_async(swp_entry_t entry) { struct page *found_page = 0, *new_page; unsigned long new_page_addr; @@ -238,7 +219,7 @@ */ lock_page(new_page); add_to_swap_cache(new_page, entry); - rw_swap_page(READ, new_page, wait); + rw_swap_page(READ, new_page); return new_page; out_free_page: diff -Nur linux.orig/mm/swapfile.c linux/mm/swapfile.c --- linux.orig/mm/swapfile.c Wed Apr 25 00:51:35 2001 +++ linux/mm/swapfile.c Wed Apr 25 00:53:24 2001 @@ -369,13 +369,15 @@ /* Get a page for the entry, using the existing swap cache page if there is one. Otherwise, get a clean page and read the swap into it. */ - page = read_swap_cache(entry); + page = read_swap_cache_async(entry); if (!page) { swap_free(entry); return -ENOMEM; } + lock_page(page); if (PageSwapCache(page)) - delete_from_swap_cache(page); + delete_from_swap_cache_nolock(page); + UnlockPage(page); read_lock(&tasklist_lock); for_each_task(p) unuse_process(p->mm, entry, page); @@ -650,7 +652,7 @@ } lock_page(virt_to_page(swap_header)); - rw_swap_page_nolock(READ, SWP_ENTRY(type,0), (char *) swap_header, 1); + rw_swap_page_nolock(READ, SWP_ENTRY(type,0), (char *) swap_header); if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10)) swap_header_version = 1;
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This archive was generated by hypermail 2b29 : Mon Apr 30 2001 - 21:00:14 EST