Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-15 Thread Suresh E. Warrier
On 04/15/2015 04:16 AM, Peter Zijlstra wrote: > On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: > >> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c >> index c9b3005..0a2d862 100644 >> --- a/kernel/trace/ring_buffer.c >> +++ b/kernel/trace/ring_buffer.c

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-15 Thread Peter Zijlstra
On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index c9b3005..0a2d862 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -482,6 +482,7 @@ struct ring_buffer_per_cpu { >

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-15 Thread Peter Zijlstra
On Tue, Apr 14, 2015 at 07:33:00PM -0500, Suresh E. Warrier wrote: > On 04/14/2015 12:13 PM, Peter Zijlstra wrote: > > On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: > >> +static u64 *get_write_timestamp(struct ring_buffer_per_cpu *cpu_buffer, > >> +

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-15 Thread Suresh E. Warrier
On 04/15/2015 04:16 AM, Peter Zijlstra wrote: On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index c9b3005..0a2d862 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -482,6

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-15 Thread Peter Zijlstra
On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index c9b3005..0a2d862 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -482,6 +482,7 @@ struct ring_buffer_per_cpu {

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-15 Thread Peter Zijlstra
On Tue, Apr 14, 2015 at 07:33:00PM -0500, Suresh E. Warrier wrote: On 04/14/2015 12:13 PM, Peter Zijlstra wrote: On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: +static u64 *get_write_timestamp(struct ring_buffer_per_cpu *cpu_buffer, + unsigned

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-14 Thread Suresh E. Warrier
On 04/14/2015 12:13 PM, Peter Zijlstra wrote: > On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: >> +static u64 *get_write_timestamp(struct ring_buffer_per_cpu *cpu_buffer, >> +unsigned long *flags) >> +{ >> +if (rb_precise_nested_write_ts()) { >>

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-14 Thread Peter Zijlstra
On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: > +static u64 *get_write_timestamp(struct ring_buffer_per_cpu *cpu_buffer, > + unsigned long *flags) > +{ > + if (rb_precise_nested_write_ts()) { > + /* > + * Ensure that we

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-14 Thread Peter Zijlstra
On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: +static u64 *get_write_timestamp(struct ring_buffer_per_cpu *cpu_buffer, + unsigned long *flags) +{ + if (rb_precise_nested_write_ts()) { + /* + * Ensure that we are

Re: [PATCH 2/2] More precise timestamps for nested writes

2015-04-14 Thread Suresh E. Warrier
On 04/14/2015 12:13 PM, Peter Zijlstra wrote: On Mon, Apr 13, 2015 at 09:38:01PM -0500, Suresh E. Warrier wrote: +static u64 *get_write_timestamp(struct ring_buffer_per_cpu *cpu_buffer, +unsigned long *flags) +{ +if (rb_precise_nested_write_ts()) { +

[PATCH 2/2] More precise timestamps for nested writes

2015-04-13 Thread Suresh E. Warrier
When tracing the behavior of multiple fio jobs running in parallel our performance team observed that some scsi_dispatch_cmd_done events appeared to occur earlier, often several microseconds earlier, than their associated scsi_dispatch_cmd_start event in the trace records. Other interrupt events

[PATCH 2/2] More precise timestamps for nested writes

2015-04-13 Thread Suresh E. Warrier
When tracing the behavior of multiple fio jobs running in parallel our performance team observed that some scsi_dispatch_cmd_done events appeared to occur earlier, often several microseconds earlier, than their associated scsi_dispatch_cmd_start event in the trace records. Other interrupt events