From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Message-Id: <20051021095658.14409.26527.sendpatchset@skynet.csn.ul.ie> Subject: [PATCH 0/8] Fragmentation Avoidance V18 Date: Fri, 21 Oct 2005 10:56:59 +0100 (IST) Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org, lhms-devel@lists.sourceforge.net Cc: Mel Gorman List-ID: Changelog since v17 o Update to 2.6.14-rc4-mm1 o Remove explicit casts where implicit casts were in place o Change __GFP_USER to __GFP_EASYRCLM, RCLM_USER to RCLM_EASY and PCPU_USER to PCPU_EASY o Print a warning and return NULL if both RCLM flags are set in the GFP flags o Reduce size of fallback_allocs o Change magic number 64 to FREE_AREA_USEMAP_SIZE o CodingStyle regressions cleanup o Move sparsemen setup_usemap() out of header o Changed fallback_balance to a mechanism that depended on zone->present_pages to avoid hotplug problems later o Many superflous parenthesis removed Changlog since v16 o Variables using bit operations now are unsigned long. Note that when used as indices, they are integers and cast to unsigned long when necessary. This is because aim9 shows regressions when used as unsigned longs throughout (~10% slowdown) o 004_showfree added to provide more debugging information o 008_stats dropped. Even with CONFIG_ALLOCSTATS disabled, it is causing severe performance regressions. No explanation as to why o for_each_rclmtype_order moved to header o More coding style cleanups Changelog since V14 (V15 not released) o Update against 2.6.14-rc3 o Resync with Joel's work. All suggestions made on fix-ups to his last set of patches should also be in here. e.g. __GFP_USER is still __GFP_USER but is better commented. o Large amount of CodingStyle, readability cleanups and corrections pointed out by Dave Hansen. o Fix CONFIG_NUMA error that corrupted per-cpu lists o Patches broken out to have one-feature-per-patch rather than more-code-per-patch o Fix fallback bug where pages for RCLM_NORCLM end up on random other free lists. Changelog since V13 o Patches are now broken out o Added per-cpu draining of userrclm pages o Brought the patch more in line with memory hotplug work o Fine-grained use of the __GFP_USER and __GFP_KERNRCLM flags o Many coding-style corrections o Many whitespace-damage corrections Changelog since V12 o Minor whitespace damage fixed as pointed by Joel Schopp Changelog since V11 o Mainly a redefiff against 2.6.12-rc5 o Use #defines for indexing into pcpu lists o Fix rounding error in the size of usemap Changelog since V10 o All allocation types now use per-cpu caches like the standard allocator o Removed all the additional buddy allocator statistic code o Elimated three zone fields that can be lived without o Simplified some loops o Removed many unnecessary calculations Changelog since V9 o Tightened what pools are used for fallbacks, less likely to fragment o Many micro-optimisations to have the same performance as the standard allocator. Modified allocator now faster than standard allocator using gcc 3.3.5 o Add counter for splits/coalescing Changelog since V8 o rmqueue_bulk() allocates pages in large blocks and breaks it up into the requested size. Reduces the number of calls to __rmqueue() o Beancounters are now a configurable option under "Kernel Hacking" o Broke out some code into inline functions to be more Hotplug-friendly o Increased the size of reserve for fallbacks from 10% to 12.5%. Changelog since V7 o Updated to 2.6.11-rc4 o Lots of cleanups, mainly related to beancounters o Fixed up a miscalculation in the bitmap size as pointed out by Mike Kravetz (thanks Mike) o Introduced a 10% reserve for fallbacks. Drastically reduces the number of kernnorclm allocations that go to the wrong places o Don't trigger OOM when large allocations are involved Changelog since V6 o Updated to 2.6.11-rc2 o Minor change to allow prezeroing to be a cleaner looking patch Changelog since V5 o Fixed up gcc-2.95 errors o Fixed up whitespace damage Changelog since V4 o No changes. Applies cleanly against 2.6.11-rc1 and 2.6.11-rc1-bk6. Applies with offsets to 2.6.11-rc1-mm1 Changelog since V3 o inlined get_pageblock_type() and set_pageblock_type() o set_pageblock_type() now takes a zone parameter to avoid a call to page_zone() o When taking from the global pool, do not scan all the low-order lists Changelog since V2 o Do not to interfere with the "min" decay o Update the __GFP_BITS_SHIFT properly. Old value broke fsync and probably anything to do with asynchronous IO Changelog since V1 o Update patch to 2.6.11-rc1 o Cleaned up bug where memory was wasted on a large bitmap o Remove code that needed the binary buddy bitmaps o Update flags to avoid colliding with __GFP_ZERO changes o Extended fallback_count bean counters to show the fallback count for each allocation type o In-code documentation Version 1 o Initial release against 2.6.9 This patch is designed to reduce fragmentation in the standard buddy allocator without impairing the performance of the allocator. High fragmentation in the standard binary buddy allocator means that high-order allocations can rarely be serviced. This patch works by dividing allocations into three different types of allocations; UserReclaimable - These are userspace pages that are easily reclaimable. This flag is set when it is known that the pages will be trivially reclaimed by writing the page out to swap or syncing with backing storage KernelReclaimable - These are pages allocated by the kernel that are easily reclaimed. This is stuff like inode caches, dcache, buffer_heads etc. These type of pages potentially could be reclaimed by dumping the caches and reaping the slabs KernelNonReclaimable - These are pages that are allocated by the kernel that are not trivially reclaimed. For example, the memory allocated for a loaded module would be in this category. By default, allocations are considered to be of this type Instead of having one global MAX_ORDER-sized array of free lists, there are four, one for each type of allocation and another reserve for fallbacks. Once a 2^MAX_ORDER block of pages it split for a type of allocation, it is added to the free-lists for that type, in effect reserving it. Hence, over time, pages of the different types can be clustered together. This means that if 2^MAX_ORDER number of pages were required, the system could linearly scan a block of pages allocated for UserReclaimable and page each of them out. Fallback is used when there are no 2^MAX_ORDER pages available and there are no free pages of the desired type. The fallback lists were chosen in a way that keeps the most easily reclaimable pages together. Three benchmark results are included all based on a 2.6.14-rc3 kernel compiled with gcc 3.4 (it is known that gcc 2.95 produces different results). The first is the output of portions of AIM9 for the vanilla allocator and the modified one; (Tests run with bench-aim9.sh from VMRegress 0.17) 2.6.14-rc4-mm1-clean ------------------------------------------------------------------------------------------------------------ Test Test Elapsed Iteration Iteration Operation Number Name Time (sec) Count Rate (loops/sec) Rate (ops/sec) ------------------------------------------------------------------------------------------------------------ 1 creat-clo 60.03 963 16.04198 16041.98 File Creations and Closes/second 2 page_test 60.02 4239 70.62646 120064.98 System Allocations & Pages/second 3 brk_test 60.02 1560 25.99134 441852.72 System Memory Allocations/second 4 jmp_test 60.01 251354 4188.53524 4188535.24 Non-local gotos/second 5 signal_test 60.01 5091 84.83586 84835.86 Signal Traps/second 6 exec_test 60.07 758 12.61861 63.09 Program Loads/second 7 fork_test 60.05 814 13.55537 1355.54 Task Creations/second 8 link_test 60.02 5326 88.73709 5590.44 Link/Unlink Pairs/second 2.6.14-rc3-mbuddy-v18 ------------------------------------------------------------------------------------------------------------ Test Test Elapsed Iteration Iteration Operation Number Name Time (sec) Count Rate (loops/sec) Rate (ops/sec) ------------------------------------------------------------------------------------------------------------ 1 creat-clo 60.05 959 15.97002 15970.02 File Creations and Closes/second 2 page_test 60.02 4239 70.62646 120064.98 System Allocations & Pages/second 3 brk_test 60.03 1552 25.85374 439513.58 System Memory Allocations/second 4 jmp_test 60.01 250647 4176.75387 4176753.87 Non-local gotos/second 5 signal_test 60.02 4967 82.75575 82755.75 Signal Traps/second 6 exec_test 60.03 747 12.44378 62.22 Program Loads/second 7 fork_test 60.02 818 13.62879 1362.88 Task Creations/second 8 link_test 60.00 5255 87.58333 5517.75 Link/Unlink Pairs/second Difference in performance operations report generated by diff-aim9.sh Clean mbuddy-v18 ---------- ---------- 1 creat-clo 15828.06 15970.02 141.96 0.90% File Creations and Closes/second 2 page_test 120339.94 120064.98 -274.96 -0.23% System Allocations & Pages/second 3 brk_test 427053.14 439513.58 12460.44 2.92% System Memory Allocations/second 4 jmp_test 4183169.47 4176753.87 -6415.60 -0.15% Non-local gotos/second 5 signal_test 84171.94 82755.75 -1416.19 -1.68% Signal Traps/second 6 exec_test 61.64 62.22 0.58 0.94% Program Loads/second 7 fork_test 1360.76 1362.88 2.12 0.16% Task Creations/second 8 link_test 5509.48 5517.75 8.27 0.15% Link/Unlink Pairs/second In this test, there were small regressions in the page_test. However, it is known that different kernel configurations, compilers and even different runs show similar varianes of +/- 3% . The second benchmark tested the CPU cache usage to make sure it was not getting clobbered. The test was to repeatedly render a large postscript file 10 times and get the average. The result is; 2.6.14-rc4-mm1-clean: Average: 43.098 real, 40.188 user, 0.03 sys 2.6.14-rc4-mm1-mbuddy-v18: Average: 43.218 real, 40.478 user, 0.05 sys So there are no adverse cache effects. The last test is to show that the allocator can satisfy more high-order allocations, especially under load, than the standard allocator. The test performs the following; 1. Start updatedb running in the background 2. Load kernel modules that tries to allocate high-order blocks on demand 3. Clean a kernel tree 4. Make 6 copies of the tree. As each copy finishes, a compile starts at -j2 5. Start compiling the primary tree 6. Sleep 1 minute while the 7 trees are being compiled 7. Use the kernel module to attempt 160 times to allocate a 2^10 block of pages - note, it only attempts 160 times, no matter how often it succeeds - An allocation is attempted every 1/10th of a second - Performance will get badly shot as it forces considerable amounts of pageout The result of the allocations under load (load averaging 18) were; 2.6.14-rc4-mm1 Clean Order: 10 Allocation type: HighMem Attempted allocations: 160 Success allocs: 22 Failed allocs: 138 DMA zone allocs: 1 Normal zone allocs: 5 HighMem zone allocs: 16 % Success: 13 2.6.14-rc4-mm1 MBuddy V18 Order: 10 Allocation type: HighMem Attempted allocations: 160 Success allocs: 41 Failed allocs: 119 DMA zone allocs: 0 Normal zone allocs: 5 HighMem zone allocs: 36 % Success: 25 One thing that had to be changed in the 2.6.14-rc4--mm1 clean test was to disable the OOM killer. During one test, the OOM killer had better results but invoked the OOM killer a very large number of times to achieve it. The patch with the placement policy never invoked the OOM killer. The above results are not very dramatic but the affect is very noticeable when the system is at rest after the test completes. After the test, the standard allocator was able to allocate 42 order-10 pages and the modified allocator allocated 152. The ability to allocate large pages under load depend heavily on the decisions of kswapd so there can be large variances in results but that is a separate problem. The results show that the modified allocator has comparable speed, has no adverse cache effects but is far less fragmented and in a better position to satisfy high-order allocations. -- Mel Gorman Part-time Phd Student Java Applications Developer University of Limerick IBM Dublin Software Lab -- 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