Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 19 Jun 2002 07:18:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 19 Jun 2002 07:18:25 -0400 Received: from loke.as.arizona.edu ([128.196.209.61]:9480 "EHLO loke.as.arizona.edu") by vger.kernel.org with ESMTP id ; Wed, 19 Jun 2002 07:18:24 -0400 Date: Wed, 19 Jun 2002 04:18:00 -0700 (MST) From: Craig Kulesa To: linux-kernel@vger.kernel.org cc: linux-mm@kvack.org Subject: [PATCH] (1/2) reverse mapping VM for 2.5.23 (rmap-13b) Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5438 Lines: 127 Where: http://loke.as.arizona.edu/~ckulesa/kernel/rmap-vm/ This patch implements Rik van Riel's patches for a reverse mapping VM atop the 2.5.23 kernel infrastructure. The principal sticky bits in the port are correct interoperability with Andrew Morton's patches to cleanup and extend the writeback and readahead code, among other things. This patch reinstates Rik's (active, inactive dirty, inactive clean) LRU list logic with the rmap information used for proper selection of pages for eviction and better page aging. It seems to do a pretty good job even for a first porting attempt. A simple, indicative test suite on a 192 MB PII machine (loading a large image in GIMP, loading other applications, heightening memory load to moderate swapout, then going back and manipulating the original Gimp image to test page aging, then closing all apps to the starting configuration) shows the following: 2.5.22 vanilla: Total kernel swapouts during test = 29068 kB Total kernel swapins during test = 16480 kB Elapsed time for test: 141 seconds 2.5.23-rmap13b: Total kernel swapouts during test = 40696 kB Total kernel swapins during test = 380 kB Elapsed time for test: 133 seconds Although rmap's page_launder evicts a ton of pages under load, it seems to swap the 'right' pages, as it doesn't need to swap them back in again. This is a good sign. [recent 2.4-aa work pretty nicely too] Various details for the curious or bored: - Tested: UP, 16 MB < mem < 256 MB, x86 arch. Untested: SMP, highmem, other archs. In particular, I didn't even attempt to port rmap-related changes to 2.5's arch/arm/mm/mm-armv.c. - page_launder() is coarse and tends to clean/flush too many pages at once. This is known behavior, but seems slightly worse in 2.5 for some reason. - pf_gfp_mask() doesn't exist in 2.5, nor does PF_NOIO. I have simply dropped the call in try_to_free_pages() in vmscan.c, but there is probably a way to reinstate its logic (i.e. avoid memory balancing I/O if the current task can't block on I/O). I didn't even attempt it. - Writeback: instead of forcing reinstating a page on the inactive list when !PageActive, page->mapping, !Pagedirty, and !PageWriteback (see mm/page-writeback.c, fs/mpage.c), I just let it go without any LRU list changes. If the page is inactive and needs attention, it'll end up on the inactive dirty list soon anyway, AFAICT. Seems okay so far, but that may be flawed/sloppy reasoning... We could always look at the page flags and reinstate the page to the appropriate LRU list (i.e. inactive clean or dirty) if this turns out to be a problem... - Make shrink_[i,d,dq]cache_memory return the result of kmem_cache_shrink(), not simply 0. Seems pointless to waste that information, since we're getting it for free. Rik's patch wants that info anyway... - Readahead and drop_behind: With the new readahead code, we have some choices regarding under what circumstances we choose to drop_behind (i.e. only drop_behind if the reads look really sequential, etc...). This patch blindly calls drop_behind at the conclusion of page_cache_readahead(). Hopefully the drop_behind code correctly interprets the new readahead indices. It *seems* to behave correctly, but a quick look by another pair of eyes would be reassuring. - A couple of trivial rmap cleanups for Rik: a) Semicolon day! System fails to boot if rmap debugging is enabled in rmap.c. Fix is to remove the extraneous semicolon in page_add_rmap(): if (!ptep_to_mm(ptep)); <-- b) The pte_chain_unlock/lock() pair between the tests for "The page is in active use" and "Anonymous process memory without backing store" in vmscan.c seems unnecessary. c) Drop PG_launder page flag, ala current 2.5 tree. d) if(page_count(page)) == 0) ---> if(!page_count(page)) and things like that... - To be consistent with 2.4-rmap, this patch includes a minimal BIO-ified port of Andrew Morton's read-latency2 patch (i.e. minus the elvtune ioctl stuff) to 2.5, from his patch sets. This adds about 7 kB to the patch. - The patch also includes compilation fixes: (2.5.22) drivers/scsi/constants.c (undeclared integer variable) drivers/pci/pci-driver.c (unresolved symbol in pcmcia_core) (2.5.23) include/linux/smp.h (define cpu_online_map for UP) kernel/ksyms.c (export default_wake_function for modules) arch/i386/i386_syms.c (export ioremap_nocache for modules) Hope this is of use to someone! It's certainly been a fun and instructive exercise for me so far. ;) I'll attempt to keep up with the 2.5 and rmap changes, fix inevitable bugs in porting, and will upload regular patches to the above URL, at least until the usual VM suspects start paying more attention to 2.5. I'll post a quick changelog to the list occasionally if and when any changes are significant, i.e. other then boring hand patching and diffing. Comments, feedback & patches always appreciated! Craig Kulesa Steward Observatory, Univ. of Arizona - 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/