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Message-ID: <20080716144008.GG24546@Krystal>
Date: Wed, 16 Jul 2008 10:40:08 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: Peter Zijlstra <peterz@...radead.org>
Cc: akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
linux-kernel@...r.kernel.org,
Masami Hiramatsu <mhiramat@...hat.com>, linux-mm@...ck.org,
Dave Hansen <haveblue@...ibm.com>,
"Frank Ch. Eigler" <fche@...hat.com>,
Hideo AOKI <haoki@...hat.com>,
Takashi Nishiie <t-nishiie@...css.fujitsu.com>,
Steven Rostedt <rostedt@...dmis.org>,
Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
Subject: Re: [patch 10/17] LTTng instrumentation - swap
* Peter Zijlstra (peterz@...radead.org) wrote:
> On Tue, 2008-07-15 at 18:26 -0400, Mathieu Desnoyers wrote:
> > plain text document attachment (lttng-instrumentation-swap.patch)
> > Instrumentation of waits caused by swap activity. Also instrumentation
> > swapon/swapoff events to keep track of active swap partitions.
> >
> > Those tracepoints are used by LTTng.
> >
> > About the performance impact of tracepoints (which is comparable to markers),
> > even without immediate values optimizations, tests done by Hideo Aoki on ia64
> > show no regression. His test case was using hackbench on a kernel where
> > scheduler instrumentation (about 5 events in code scheduler code) was added.
> > See the "Tracepoints" patch header for performance result detail.
> >
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> > CC: linux-mm@...ck.org
> > CC: Dave Hansen <haveblue@...ibm.com>
> > CC: Masami Hiramatsu <mhiramat@...hat.com>
> > CC: 'Peter Zijlstra' <peterz@...radead.org>
> > CC: "Frank Ch. Eigler" <fche@...hat.com>
> > CC: 'Ingo Molnar' <mingo@...e.hu>
> > CC: 'Hideo AOKI' <haoki@...hat.com>
> > CC: Takashi Nishiie <t-nishiie@...css.fujitsu.com>
> > CC: 'Steven Rostedt' <rostedt@...dmis.org>
> > CC: Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
> > ---
> > include/trace/swap.h | 20 ++++++++++++++++++++
> > mm/memory.c | 2 ++
> > mm/page_io.c | 2 ++
> > mm/swapfile.c | 4 ++++
> > 4 files changed, 28 insertions(+)
> >
> > Index: linux-2.6-lttng/mm/memory.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/mm/memory.c 2008-07-15 13:54:46.000000000 -0400
> > +++ linux-2.6-lttng/mm/memory.c 2008-07-15 14:02:54.000000000 -0400
> > @@ -51,6 +51,7 @@
> > #include <linux/init.h>
> > #include <linux/writeback.h>
> > #include <linux/memcontrol.h>
> > +#include <trace/swap.h>
> >
> > #include <asm/pgalloc.h>
> > #include <asm/uaccess.h>
> > @@ -2213,6 +2214,7 @@ static int do_swap_page(struct mm_struct
> > /* Had to read the page from swap area: Major fault */
> > ret = VM_FAULT_MAJOR;
> > count_vm_event(PGMAJFAULT);
> > + trace_swap_in(page, entry);
> > }
> >
> > if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
> > Index: linux-2.6-lttng/mm/page_io.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/mm/page_io.c 2008-07-15 13:54:46.000000000 -0400
> > +++ linux-2.6-lttng/mm/page_io.c 2008-07-15 14:02:54.000000000 -0400
> > @@ -17,6 +17,7 @@
> > #include <linux/bio.h>
> > #include <linux/swapops.h>
> > #include <linux/writeback.h>
> > +#include <trace/swap.h>
> > #include <asm/pgtable.h>
> >
> > static struct bio *get_swap_bio(gfp_t gfp_flags, pgoff_t index,
> > @@ -114,6 +115,7 @@ int swap_writepage(struct page *page, st
> > rw |= (1 << BIO_RW_SYNC);
> > count_vm_event(PSWPOUT);
> > set_page_writeback(page);
> > + trace_swap_out(page);
> > unlock_page(page);
> > submit_bio(rw, bio);
> > out:
> > Index: linux-2.6-lttng/mm/swapfile.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/mm/swapfile.c 2008-07-15 13:54:46.000000000 -0400
> > +++ linux-2.6-lttng/mm/swapfile.c 2008-07-15 14:02:54.000000000 -0400
> > @@ -32,6 +32,7 @@
> > #include <asm/pgtable.h>
> > #include <asm/tlbflush.h>
> > #include <linux/swapops.h>
> > +#include <trace/swap.h>
> >
> > DEFINE_SPINLOCK(swap_lock);
> > unsigned int nr_swapfiles;
> > @@ -1310,6 +1311,7 @@ asmlinkage long sys_swapoff(const char _
> > swap_map = p->swap_map;
> > p->swap_map = NULL;
> > p->flags = 0;
> > + trace_swap_file_close(swap_file);
> > spin_unlock(&swap_lock);
> > mutex_unlock(&swapon_mutex);
> > vfree(swap_map);
> > @@ -1695,6 +1697,7 @@ asmlinkage long sys_swapon(const char __
> > } else {
> > swap_info[prev].next = p - swap_info;
> > }
> > + trace_swap_file_open(swap_file, name);
> > spin_unlock(&swap_lock);
> > mutex_unlock(&swapon_mutex);
> > error = 0;
> > @@ -1796,6 +1799,7 @@ get_swap_info_struct(unsigned type)
> > {
> > return &swap_info[type];
> > }
> > +EXPORT_SYMBOL_GPL(get_swap_info_struct);
>
> I'm not too happy with this export.
>
Would it make more sense to turn get_swap_info_struct into a static
inline in swap.h ?
Mathieu
> >
> > /*
> > * swap_lock prevents swap_map being freed. Don't grab an extra
> > Index: linux-2.6-lttng/include/trace/swap.h
> > ===================================================================
> > --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> > +++ linux-2.6-lttng/include/trace/swap.h 2008-07-15 14:02:54.000000000 -0400
> > @@ -0,0 +1,20 @@
> > +#ifndef _TRACE_SWAP_H
> > +#define _TRACE_SWAP_H
> > +
> > +#include <linux/swap.h>
> > +#include <linux/tracepoint.h>
> > +
> > +DEFINE_TRACE(swap_in,
> > + TPPROTO(struct page *page, swp_entry_t entry),
> > + TPARGS(page, entry));
> > +DEFINE_TRACE(swap_out,
> > + TPPROTO(struct page *page),
> > + TPARGS(page));
> > +DEFINE_TRACE(swap_file_open,
> > + TPPROTO(struct file *file, char *filename),
> > + TPARGS(file, filename));
> > +DEFINE_TRACE(swap_file_close,
> > + TPPROTO(struct file *file),
> > + TPARGS(file));
> > +
> > +#endif
> >
>
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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