Messages in this thread Patch in this message | | | Date | Sun, 26 May 2002 13:40:20 -0700 | From | Andrew Morton <> | Subject | [patch 5/18] mark swapout pages PageWriteback() |
| |
Pages which are under writeout to swap are locked, and not PageWriteback(). So page allocators do not throttle against them in shrink_caches().
This causes enormous list scans and general coma under really heavy swapout loads.
One fix would be to teach shrink_cache() to wait on PG_locked for swap pages. The other approach is to set both PG_locked and PG_writeback for swap pages so they can be handled in the same manner as file-backed pages in shrink_cache().
This patch takes the latter approach.
=====================================
--- 2.5.18/fs/buffer.c~swap-writeback Sat May 25 23:26:46 2002 +++ 2.5.18-akpm/fs/buffer.c Sun May 26 00:50:20 2002 @@ -544,6 +544,14 @@ static void end_buffer_async_read(struct */ if (page_uptodate && !PageError(page)) SetPageUptodate(page); + + /* + * swap page handling is a bit hacky. A standalone completion handler + * for swapout pages would fix that up. swapin can use this function. + */ + if (PageSwapCache(page) && PageWriteback(page)) + end_page_writeback(page); + unlock_page(page); return; @@ -2271,6 +2279,9 @@ int brw_kiovec(int rw, int nr, struct ki * calls block_flushpage() under spinlock and hits a locked buffer, and * schedules under spinlock. Another approach would be to teach * find_trylock_page() to also trylock the page's writeback flags. + * + * Swap pages are also marked PageWriteback when they are being written + * so that memory allocators will throttle on them. */ int brw_page(int rw, struct page *page, struct block_device *bdev, sector_t b[], int size) @@ -2301,6 +2312,11 @@ int brw_page(int rw, struct page *page, bh = bh->b_this_page; } while (bh != head); + if (rw == WRITE) { + BUG_ON(PageWriteback(page)); + SetPageWriteback(page); + } + /* Stage 2: start the IO */ do { struct buffer_head *next = bh->b_this_page; --- 2.5.18/mm/swap_state.c~swap-writeback Sat May 25 23:26:46 2002 +++ 2.5.18-akpm/mm/swap_state.c Sun May 26 00:50:19 2002 @@ -36,10 +36,8 @@ static int swap_writepage(struct page *p * swapper_space doesn't have a real inode, so it gets a special vm_writeback() * so we don't need swap special cases in generic_vm_writeback(). * - * FIXME: swap pages are locked, but not PageWriteback while under writeout. - * This will confuse throttling in shrink_cache(). It may be advantageous to - * set PG_writeback against swap pages while they're also locked. Either that, - * or special-case swap pages in shrink_cache(). + * Swap pages are PageLocked and PageWriteback while under writeout so that + * memory allocators will throttle against them. */ static int swap_vm_writeback(struct page *page, int *nr_to_write) {
- - 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/
| |