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Date: Thu, 18 Feb 2010 15:28:50 +0530 From: Balbir Singh <balbir@...ux.vnet.ibm.com> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Cc: Wu Fengguang <fengguang.wu@...el.com>, Ingo Molnar <mingo@...e.hu>, Chris Frost <frost@...ucla.edu>, Steven Rostedt <rostedt@...dmis.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Frederic Weisbecker <fweisbec@...il.com>, Keiichi KII <k-keiichi@...jp.nec.com>, Andrew Morton <akpm@...ux-foundation.org>, Jason Baron <jbaron@...hat.com>, Hitoshi Mitake <mitake@....info.waseda.ac.jp>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "lwoodman@...hat.com" <lwoodman@...hat.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Tom Zanussi <tzanussi@...il.com>, "riel@...hat.com" <riel@...hat.com>, Munehiro Ikeda <m-ikeda@...jp.nec.com>, Atsushi Tsuji <a-tsuji@...jp.nec.com> Subject: Re: [RFC PATCH -tip 0/2 v3] pagecache tracepoints proposal * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2010-02-18 14:34:29]: > On Mon, 8 Feb 2010 23:54:50 +0800 > Wu Fengguang <fengguang.wu@...el.com> wrote: > > > Hi Ingo, > > > > > Note that there's also these older experimental commits in tip:tracing/mm > > > that introduce the notion of 'object collections' and adds the ability to > > > trace them: > > > > > > 3383e37: tracing, page-allocator: Add a postprocessing script for page-allocator-related ftrace events > > > c33b359: tracing, page-allocator: Add trace event for page traffic related to the buddy lists > > > 0d524fb: tracing, mm: Add trace events for anti-fragmentation falling back to other migratetypes > > > b9a2817: tracing, page-allocator: Add trace events for page allocation and page freeing > > > 08b6cb8: perf_counter tools: Provide default bfd_demangle() function in case it's not around > > > eb46710: tracing/mm: rename 'trigger' file to 'dump_range' > > > 1487a7a: tracing/mm: fix mapcount trace record field > > > dcac8cd: tracing/mm: add page frame snapshot trace > > > > > > this concept, if refreshed a bit and extended to the page cache, would allow > > > the recording/snapshotting of the MM state of all currently present pages in > > > the page-cache - a possibly nice addition to the dynamic technique you apply > > > in your patches. > > > > > > there's similar "object collections" work underway for 'perf lock' btw., by > > > Hitoshi Mitake and Frederic. > > > > > > So there's lots of common ground and lots of interest. > > > > Here is a scratch patch to exercise the "object collections" idea :) > > > > Interestingly, the pagecache walk is pretty fast, while copying out the trace > > data takes more time: > > > > # time (echo / > walk-fs) > > (; echo / > walk-fs; ) 0.01s user 0.11s system 82% cpu 0.145 total > > > > # time wc /debug/tracing/trace > > 4570 45893 551282 /debug/tracing/trace > > wc /debug/tracing/trace 0.75s user 0.55s system 88% cpu 1.470 total > > > > # time (cat /debug/tracing/trace > /dev/shm/t) > > (; cat /debug/tracing/trace > /dev/shm/t; ) 0.04s user 0.49s system 95% cpu 0.548 total > > > > # time (dd if=/debug/tracing/trace of=/dev/shm/t bs=1M) > > 0+138 records in > > 0+138 records out > > 551282 bytes (551 kB) copied, 0.380454 s, 1.4 MB/s > > (; dd if=/debug/tracing/trace of=/dev/shm/t bs=1M; ) 0.09s user 0.48s system 96% cpu 0.600 total > > > > The patch is based on tip/tracing/mm. > > > > Thanks, > > Fengguang > > --- > > tracing: pagecache object collections > > > > This dumps > > - all cached files of a mounted fs (the inode-cache) > > - all cached pages of a cached file (the page-cache) > > > > Usage and Sample output: > > > > # echo / > /debug/tracing/objects/mm/pages/walk-fs > > # head /debug/tracing/trace > > > > # tracer: nop > > # > > # TASK-PID CPU# TIMESTAMP FUNCTION > > # | | | | | > > zsh-3078 [000] 526.272587: dump_inode: ino=102223 size=169291 cached=172032 age=9 dirty=6 dev=0:15 file=<TODO> > > zsh-3078 [000] 526.274260: dump_pagecache_range: index=0 len=41 flags=10000000000002c count=1 mapcount=0 > > zsh-3078 [000] 526.274340: dump_pagecache_range: index=41 len=1 flags=10000000000006c count=1 mapcount=0 > > zsh-3078 [000] 526.274401: dump_inode: ino=8966 size=442 cached=4096 age=49 dirty=0 dev=0:15 file=<TODO> > > zsh-3078 [000] 526.274425: dump_pagecache_range: index=0 len=1 flags=10000000000002c count=1 mapcount=0 > > zsh-3078 [000] 526.274440: dump_inode: ino=8964 size=4096 cached=0 age=49 dirty=0 dev=0:15 file=<TODO> > > > > Here "age" is either age from inode create time, or from last dirty time. > > > > TODO: > > > > correctness > > - show file path name > > XXX: can trace_seq_path() be called directly inside TRACE_EVENT()? > > - reliably prevent ring buffer overflow, > > by replacing cond_resched() with some wait function > > (eg. wait until 2+ pages are free in ring buffer) > > - use stable_page_flags() in recent kernel > > > > output style > > - use plain tracing output format (no fancy TASK-PID/.../FUNCTION fields) > > - clear ring buffer before dumping the objects? > > - output format: key=value pairs ==> header + tabbed values? > > - add filtering options if necessary > > > > Can we dump page's cgroup ? If so, I'm happy. > Maybe > == > struct page_cgroup *pc = lookup_page_cgroup(page); > struct mem_cgroup *mem = pc->mem_cgroup; > shodt mem_cgroup_id = mem->css.css_id; > > And statistics can be counted per css_id. > Good idea, all of this needs to happen with a check to see if memcg is enabled/disabled at boot as well. pc can be NULL if CONFIG_CGROUP_MEM_RES_CTLR is not enabled. > And then, some output like > > dump_pagecache_range: index=0 len=1 flags=10000000000002c count=1 mapcount=0 file=XXX memcg=group_A:x,group_B:y > > Is it okay to add a new field after your work finish ? > -- Three Cheers, Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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