The following series implements page cache control, this is a split out version of patch 1 of version 3 of the page cache optimization patches posted earlier at http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg43654.html Christoph Lamater recommended splitting out patch 1, which is what this series does Detailed Description ==================== This patch implements unmapped page cache control via preferred page cache reclaim. The current patch hooks into kswapd and reclaims page cache if the user has requested for unmapped page control. This is useful in the following scenario - In a virtualized environment with cache=writethrough, we see double caching - (one in the host and one in the guest). As we try to scale guests, cache usage across the system grows. The goal of this patch is to reclaim page cache when Linux is running as a guest and get the host to hold the page cache and manage it. There might be temporary duplication, but in the long run, memory in the guests would be used for mapped pages. - The option is controlled via a boot option and the administrator can selectively turn it on, on a need to use basis. A lot of the code is borrowed from zone_reclaim_mode logic for __zone_reclaim(). One might argue that the with ballooning and KSM this feature is not very useful, but even with ballooning, we need extra logic to balloon multiple VM machines and it is hard to figure out the correct amount of memory to balloon. With these patches applied, each guest has a sufficient amount of free memory available, that can be easily seen and reclaimed by the balloon driver. The additional memory in the guest can be reused for additional applications or used to start additional guests/balance memory in the host. KSM currently does not de-duplicate host and guest page cache. The goal of this patch is to help automatically balance unmapped page cache when instructed to do so. There are some magic numbers in use in the code, UNMAPPED_PAGE_RATIO and the number of pages to reclaim when unmapped_page_control argument is supplied. These numbers were chosen to avoid aggressiveness in reaping page cache ever so frequently, at the same time providing control. The sysctl for min_unmapped_ratio provides further control from within the guest on the amount of unmapped pages to reclaim. For a single VM - running kernbench Enabled Optimal load -j 8 run number 1... Optimal load -j 8 run number 2... Optimal load -j 8 run number 3... Optimal load -j 8 run number 4... Optimal load -j 8 run number 5... Average Optimal load -j 8 Run (std deviation): Elapsed Time 273.726 (1.2683) User Time 190.014 (0.589941) System Time 298.758 (1.72574) Percent CPU 178 (0) Context Switches 119953 (865.74) Sleeps 38758 (795.074) Disabled Optimal load -j 8 run number 1... Optimal load -j 8 run number 2... Optimal load -j 8 run number 3... Optimal load -j 8 run number 4... Optimal load -j 8 run number 5... Average Optimal load -j 8 Run (std deviation): Elapsed Time 272.672 (0.453178) User Time 189.7 (0.718157) System Time 296.77 (0.845606) Percent CPU 178 (0) Context Switches 118822 (277.434) Sleeps 37542.8 (545.922) More data on the test results with the earlier patch is at http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg43655.html --- Balbir Singh (3): Move zone_reclaim() outside of CONFIG_NUMA Refactor zone_reclaim, move reusable functionality outside Provide control over unmapped pages include/linux/mmzone.h | 4 +- include/linux/swap.h | 5 +- mm/page_alloc.c | 7 ++- mm/vmscan.c | 109 +++++++++++++++++++++++++++++++++++++++++------- 4 files changed, 104 insertions(+), 21 deletions(-) -- Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>