On Mon 17-10-16 13:31:57, Janani Ravichandran wrote: > > > On Oct 17, 2016, at 1:24 PM, Janani Ravichandran <janani.rvchndrn@xxxxxxxxx> wrote: > > > > > > On Sun, Oct 16, 2016 at 3:33 AM, Michal Hocko <mhocko@xxxxxxxxxx <mailto:mhocko@xxxxxxxxxx>> wrote: > > > > trace_mm_page_alloc will tell you details about the allocation, like > > gfp mask, order but it doesn't tell you how long the allocation took at > > its current form. So either you have to note jiffies at the allocation > > start and then add the end-start in the trace point or we really need > > another trace point to note the start. The later has an advantage that > > we do not add unnecessary load for jiffies when the tracepoint is > > disabled. > > The function graph tracer can tell us how long alloc_pages_nodemask() took. > Can’t that, combined with the context information given by trace_mm_page_alloc > give us what we want? Correct me if I am wrong. yes, function_graph tracer will give you _some_ information but it will not have the context you are looking for, right? See the following example ------------------------------------------ 0) x-www-b-22756 => x-termi-4083 ------------------------------------------ 0) | __alloc_pages_nodemask() { 0) | /* mm_page_alloc: page=ffffea000411b380 pfn=1066702 order=0 migratetype=0 gfp_flags=GFP_KERNEL */ 0) 3.328 us | } 3) | __alloc_pages_nodemask() { 3) | /* mm_page_alloc: page=ffffea0008f1f6c0 pfn=2344923 order=0 migratetype=0 gfp_flags=GFP_KERNEL */ 3) 1.011 us | } 0) | __alloc_pages_nodemask() { 0) | /* mm_page_alloc: page=ffffea000411b380 pfn=1066702 order=0 migratetype=0 gfp_flags=GFP_KERNEL */ 0) 0.587 us | } 3) | __alloc_pages_nodemask() { 3) | /* mm_page_alloc: page=ffffea0008f1f6c0 pfn=2344923 order=0 migratetype=0 gfp_flags=GFP_KERNEL */ 3) 1.125 us | } How do I know which process has performed those allocations? I know that CPU0 should be running x-termi-4083 but what is running on other CPUs? Let me explain my usecase I am very interested in. Say I that a usespace application is not performing well. I would like to see some statistics about memory allocations performed for that app - are there few outliers or the allocation stalls increase gradually? Where do we spend time during that allocation? Reclaim LRU pages? Compaction or the slab shrinkers? To answer those questions I need to track particular events (alocation, reclaim, compaction) to the process and know how long each step took. Maybe we can reconstruct something from the above output but it is a major PITA. If we either hard start/stop pairs for each step (which we already do have for reclaim, compaction AFAIR) then this is an easy scripting. Another option would be to have only a single tracepoint for each step with a timing information. See my point? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>