user/sven/linux.git/mm/vmstat.c, branch v4.0

vmstat: Reduce time interval to stat update on idle cpu

2015-02-12T01:06:07Z

It was noted that the vm stat shepherd runs every 2 seconds and that the vmstat update is then scheduled 2 seconds in the future. This yields an interval of double the time interval which is not desired. Change the shepherd so that it does not delay the vmstat update on the other cpu. We stil have to use schedule_delayed_work since we are using a delayed_work_struct but we can set the delay to 0. Signed-off-by: Christoph Lameter Acked-by: Michal Hocko Cc: Vinayak Menon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

vmstat: do not use deferrable delayed work for vmstat_update

2015-02-12T01:06:07Z

Vinayak Menon has reported that an excessive number of tasks was throttled in the direct reclaim inside too_many_isolated() because NR_ISOLATED_FILE was relatively high compared to NR_INACTIVE_FILE. However it turned out that the real number of NR_ISOLATED_FILE was 0 and the per-cpu vm_stat_diff wasn't transferred into the global counter. vmstat_work which is responsible for the sync is defined as deferrable delayed work which means that the defined timeout doesn't wake up an idle CPU. A CPU might stay in an idle state for a long time and general effort is to keep such a CPU in this state as long as possible which might lead to all sorts of troubles for vmstat consumers as can be seen with the excessive direct reclaim throttling. This patch basically reverts 39bf6270f524 ("VM statistics: Make timer deferrable") but it shouldn't cause any problems for idle CPUs because only CPUs with an active per-cpu drift are woken up since 7cc36bbddde5 ("vmstat: on-demand vmstat workers v8") and CPUs which are idle for a longer time shouldn't have per-cpu drift. Fixes: 39bf6270f524 (VM statistics: Make timer deferrable) Signed-off-by: Michal Hocko Reported-by: Vinayak Menon Acked-by: Christoph Lameter Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Mel Gorman Cc: Minchan Kim Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/vmstat.c: fix/cleanup ifdefs

2015-02-10T22:30:30Z

CONFIG_COMPACTION=y, CONFIG_DEBUG_FS=n: mm/vmstat.c:690: warning: 'frag_start' defined but not used mm/vmstat.c:702: warning: 'frag_next' defined but not used mm/vmstat.c:710: warning: 'frag_stop' defined but not used mm/vmstat.c:715: warning: 'walk_zones_in_node' defined but not used It's all a bit of a tangly mess and it's unclear why CONFIG_COMPACTION figures in there at all. Move frag_start/frag_next/frag_stop and migratetype_names[] into the existing CONFIG_PROC_FS block. walk_zones_in_node() gets a special ifdef. Also move the #include lines up to where #include lines live. [axel.lin@ingics.com: fix build error when !CONFIG_PROC_FS] Signed-off-by: Axel Lin Cc: Mel Gorman Cc: Joonsoo Kim Cc: Mel Gorman Cc: Joonsoo Kim Tested-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm,vmacache: count number of system-wide flushes

2014-12-13T20:42:48Z

These flushes deal with sequence number overflows, such as for long lived threads. These are rare, but interesting from a debugging PoV. As such, display the number of flushes when vmacache debugging is enabled. Signed-off-by: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_owner: keep track of page owners

2014-12-13T20:42:48Z

This is the page owner tracking code which is introduced so far ago. It is resident on Andrew's tree, though, nobody tried to upstream so it remain as is. Our company uses this feature actively to debug memory leak or to find a memory hogger so I decide to upstream this feature. This functionality help us to know who allocates the page. When allocating a page, we store some information about allocation in extra memory. Later, if we need to know status of all pages, we can get and analyze it from this stored information. In previous version of this feature, extra memory is statically defined in struct page, but, in this version, extra memory is allocated outside of struct page. It enables us to turn on/off this feature at boottime without considerable memory waste. Although we already have tracepoint for tracing page allocation/free, using it to analyze page owner is rather complex. We need to enlarge the trace buffer for preventing overlapping until userspace program launched. And, launched program continually dump out the trace buffer for later analysis and it would change system behaviour with more possibility rather than just keeping it in memory, so bad for debug. Moreover, we can use page_owner feature further for various purposes. For example, we can use it for fragmentation statistics implemented in this patch. And, I also plan to implement some CMA failure debugging feature using this interface. I'd like to give the credit for all developers contributed this feature, but, it's not easy because I don't know exact history. Sorry about that. Below is people who has "Signed-off-by" in the patches in Andrew's tree. Contributor: Alexander Nyberg Mel Gorman Dave Hansen Minchan Kim Michal Nazarewicz Andrew Morton Jungsoo Son Signed-off-by: Joonsoo Kim Cc: Mel Gorman Cc: Johannes Weiner Cc: Minchan Kim Cc: Dave Hansen Cc: Michal Nazarewicz Cc: Jungsoo Son Cc: Ingo Molnar Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

vmstat: on-demand vmstat workers V8

2014-10-10T02:26:02Z

vmstat workers are used for folding counter differentials into the zone, per node and global counters at certain time intervals. They currently run at defined intervals on all processors which will cause some holdoff for processors that need minimal intrusion by the OS. The current vmstat_update mechanism depends on a deferrable timer firing every other second by default which registers a work queue item that runs on the local CPU, with the result that we have 1 interrupt and one additional schedulable task on each CPU every 2 seconds If a workload indeed causes VM activity or multiple tasks are running on a CPU, then there are probably bigger issues to deal with. However, some workloads dedicate a CPU for a single CPU bound task. This is done in high performance computing, in high frequency financial applications, in networking (Intel DPDK, EZchip NPS) and with the advent of systems with more and more CPUs over time, this may become more and more common to do since when one has enough CPUs one cares less about efficiently sharing a CPU with other tasks and more about efficiently monopolizing a CPU per task. The difference of having this timer firing and workqueue kernel thread scheduled per second can be enormous. An artificial test measuring the worst case time to do a simple "i++" in an endless loop on a bare metal system and under Linux on an isolated CPU with dynticks and with and without this patch, have Linux match the bare metal performance (~700 cycles) with this patch and loose by couple of orders of magnitude (~200k cycles) without it[*]. The loss occurs for something that just calculates statistics. For networking applications, for example, this could be the difference between dropping packets or sustaining line rate. Statistics are important and useful, but it would be great if there would be a way to not cause statistics gathering produce a huge performance difference. This patche does just that. This patch creates a vmstat shepherd worker that monitors the per cpu differentials on all processors. If there are differentials on a processor then a vmstat worker local to the processors with the differentials is created. That worker will then start folding the diffs in regular intervals. Should the worker find that there is no work to be done then it will make the shepherd worker monitor the differentials again. With this patch it is possible then to have periods longer than 2 seconds without any OS event on a "cpu" (hardware thread). The patch shows a very minor increased in system performance. hackbench -s 512 -l 2000 -g 15 -f 25 -P Results before the patch: Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks) Each sender will pass 2000 messages of 512 bytes Time: 4.992 Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks) Each sender will pass 2000 messages of 512 bytes Time: 4.971 Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks) Each sender will pass 2000 messages of 512 bytes Time: 5.063 Hackbench after the patch: Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks) Each sender will pass 2000 messages of 512 bytes Time: 4.973 Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks) Each sender will pass 2000 messages of 512 bytes Time: 4.990 Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks) Each sender will pass 2000 messages of 512 bytes Time: 4.993 [fengguang.wu@intel.com: cpu_stat_off can be static] Signed-off-by: Christoph Lameter Reviewed-by: Gilad Ben-Yossef Cc: Frederic Weisbecker Cc: Thomas Gleixner Cc: Tejun Heo Cc: John Stultz Cc: Mike Frysinger Cc: Minchan Kim Cc: Hakan Akkan Cc: Max Krasnyansky Cc: "Paul E. McKenney" Cc: Hugh Dickins Cc: Viresh Kumar Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Fengguang Wu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/balloon_compaction: add vmstat counters and kpageflags bit

2014-10-10T02:26:01Z

Always mark pages with PageBalloon even if balloon compaction is disabled and expose this mark in /proc/kpageflags as KPF_BALLOON. Also this patch adds three counters into /proc/vmstat: "balloon_inflate", "balloon_deflate" and "balloon_migrate". They accumulate balloon activity. Current size of balloon is (balloon_inflate - balloon_deflate) pages. All generic balloon code now gathered under option CONFIG_MEMORY_BALLOON. It should be selected by ballooning driver which wants use this feature. Currently virtio-balloon is the only user. Signed-off-by: Konstantin Khlebnikov Cc: Rafael Aquini Cc: Andrey Ryabinin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: vmscan: only update per-cpu thresholds for online CPU

2014-08-07T01:01:20Z

When kswapd is awake reclaiming, the per-cpu stat thresholds are lowered to get more accurate counts to avoid breaching watermarks. This threshold update iterates over all possible CPUs which is unnecessary. Only online CPUs need to be updated. If a new CPU is onlined, refresh_zone_stat_thresholds() will set the thresholds correctly. Signed-off-by: Mel Gorman Acked-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: move zone->pages_scanned into a vmstat counter

2014-08-07T01:01:20Z

zone->pages_scanned is a write-intensive cache line during page reclaim and it's also updated during page free. Move the counter into vmstat to take advantage of the per-cpu updates and do not update it in the free paths unless necessary. On a small UMA machine running tiobench the difference is marginal. On a 4-node machine the overhead is more noticable. Note that automatic NUMA balancing was disabled for this test as otherwise the system CPU overhead is unpredictable. 3.16.0-rc3 3.16.0-rc3 3.16.0-rc3 vanillarearrange-v5 vmstat-v5 User 746.94 759.78 774.56 System 65336.22 58350.98 32847.27 Elapsed 27553.52 27282.02 27415.04 Note that the overhead reduction will vary depending on where exactly pages are allocated and freed. Signed-off-by: Mel Gorman Acked-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: rearrange zone fields into read-only, page alloc, statistics and page reclaim lines

2014-08-07T01:01:20Z

The arrangement of struct zone has changed over time and now it has reached the point where there is some inappropriate sharing going on. On x86-64 for example o The zone->node field is shared with the zone lock and zone->node is accessed frequently from the page allocator due to the fair zone allocation policy. o span_seqlock is almost never used by shares a line with free_area o Some zone statistics share a cache line with the LRU lock so reclaim-intensive and allocator-intensive workloads can bounce the cache line on a stat update This patch rearranges struct zone to put read-only and read-mostly fields together and then splits the page allocator intensive fields, the zone statistics and the page reclaim intensive fields into their own cache lines. Note that the type of lowmem_reserve changes due to the watermark calculations being signed and avoiding a signed/unsigned conversion there. On the test configuration I used the overall size of struct zone shrunk by one cache line. On smaller machines, this is not likely to be noticable. However, on a 4-node NUMA machine running tiobench the system CPU overhead is reduced by this patch. 3.16.0-rc3 3.16.0-rc3 vanillarearrange-v5r9 User 746.94 759.78 System 65336.22 58350.98 Elapsed 27553.52 27282.02 Signed-off-by: Mel Gorman Acked-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds