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Date: Tue, 22 Aug 2017 17:58:34 +0000
From: "Liang, Kan" <kan.liang@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: "mingo@...hat.com" <mingo@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"acme@...nel.org" <acme@...nel.org>,
"jolsa@...hat.com" <jolsa@...hat.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"eranian@...gle.com" <eranian@...gle.com>,
"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: RE: [PATCH V5] perf: Add PERF_SAMPLE_PHYS_ADDR
>
> On Thu, Aug 17, 2017 at 02:17:23PM -0400, kan.liang@...el.com wrote:
> > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > index a3b873f..6783c69 100644
> > --- a/include/linux/perf_event.h
> > +++ b/include/linux/perf_event.h
> > @@ -944,6 +944,8 @@ struct perf_sample_data {
> >
> > struct perf_regs regs_intr;
> > u64 stack_user_size;
> > +
> > + u64 phys_addr;
> > } ____cacheline_aligned;
> >
> > /* default value for data source */
> > @@ -964,6 +966,7 @@ static inline void perf_sample_data_init(struct
> perf_sample_data *data,
> > data->weight = 0;
> > data->data_src.val = PERF_MEM_NA;
> > data->txn = 0;
> > + data->phys_addr = 0;
> > }
>
> So this is very unfortunate...
>
> struct perf_sample_data {
> u64 addr; /* 0 8 */
> struct perf_raw_record * raw; /* 8 8 */
> struct perf_branch_stack * br_stack; /* 16 8 */
> u64 period; /* 24 8 */
> u64 weight; /* 32 8 */
> u64 txn; /* 40 8 */
> union perf_mem_data_src data_src; /* 48 8 */
> u64 type; /* 56 8 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> u64 ip; /* 64 8 */
> struct {
> u32 pid; /* 72 4 */
> u32 tid; /* 76 4 */
> } tid_entry; /* 72 8 */
> u64 time; /* 80 8 */
> u64 id; /* 88 8 */
> u64 stream_id; /* 96 8 */
> struct {
> u32 cpu; /* 104 4 */
> u32 reserved; /* 108 4 */
> } cpu_entry; /* 104 8 */
> struct perf_callchain_entry * callchain; /* 112 8 */
> struct perf_regs regs_user; /* 120 16 */
> /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
> struct pt_regs regs_user_copy; /* 136 168 */
> /* --- cacheline 4 boundary (256 bytes) was 48 bytes ago --- */
> struct perf_regs regs_intr; /* 304 16 */
> /* --- cacheline 5 boundary (320 bytes) --- */
> u64 stack_user_size; /* 320 8 */
>
> /* size: 384, cachelines: 6, members: 19 */
> /* padding: 56 */
> };
>
>
> static inline void perf_sample_data_init(struct perf_sample_data *data,
> u64 addr, u64 period)
> {
> /* remaining struct members initialized in perf_prepare_sample() */
> data->addr = addr;
> data->raw = NULL;
> data->br_stack = NULL;
> data->period = period;
> data->weight = 0;
> data->data_src.val = PERF_MEM_NA;
> data->txn = 0;
> }
>
> You'll note that that only touches the first cacheline of the data structure,
> and you just wrecked that. Back when I did that this made a measurable
> difference.
It looks there is still one room in cacheline 1.
Could I use it?
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index b14095b..bcd1007 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -915,6 +915,7 @@ struct perf_sample_data {
u64 weight;
u64 txn;
union perf_mem_data_src data_src;
+ u64 phys_addr;
/*
* The other fields, optionally {set,used} by
@@ -964,6 +966,7 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
data->weight = 0;
data->data_src.val = PERF_MEM_NA;
data->txn = 0;
+ data->phys_addr = 0;
}
Thanks,
Kan
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