Re: [PATCH v4 00/12] perf c2c: Support display for Arm64
From: Ian Rogers
Date: Thu Jun 02 2022 - 12:59:50 EST
On Wed, Jun 1, 2022 at 3:25 AM Leo Yan <leo.yan@xxxxxxxxxx> wrote:
>
> Hi Joe,
>
> On Tue, May 31, 2022 at 02:44:07PM -0400, Joe Mario wrote:
>
> [...]
>
> > Hi Leo:
> > I built a new perf with your patches and ran it on a 2-numa node Neoverse platform.
> > I then ran my simple test that creates reader and writer threads to tug on the same cacheline.
> > The c2c output is appended below.
> >
> > The output looks good, especially where you've broken out the (average) cycles for local and remote peer loads.
> > And I'm glad to see you fixed the "Node" column. I use that a lot to help detect remote node accesses.
>
> Thanks a lot for your testing and suggestions, which are really helpful!
>
> > And the "PA cnt" field is working as well, which is important to see if numa_balance is moving the data around.
>
> Good to know this. To be honest, before I didn't note for "PA cnt"
> metric, I checked a bit for the code, this metrics is very useful to
> understand how it's severe that a cache line is accessed from different
> addresses, so we can get sense how a cache line is hammered.
>
> > =================================================
> > Shared Data Cache Line Table
> > =================================================
> > #
> > # ----------- Cacheline ---------- Peer ------- Load Peer ------- Total Total Total --------- Stores -------- ----- Core Load Hit ----- - LLC Load Hit -- - RMT Load Hit -- --- Load Dram ----
> > # Index Address Node PA cnt Snoop Total Local Remote records Loads Stores L1Hit L1Miss N/A FB L1 L2 LclHit LclHitm RmtHit RmtHitm Lcl Rmt
> > # ..... .................. .... ...... ....... ....... ....... ....... ....... ....... ....... ....... ....... ....... ....... ....... ....... ........ ....... ........ ....... ........ ........
> > #
> > 0 0x422140 0 6904 74.86% 137 131 6 148008 144970 3038 0 0 3038 0 144833 120 11 0 6 0 0 0
> > 1 0xffffd976e63ae5c0 1 6 3.83% 7 7 0 15 15 0 0 0 0 0 8 4 3 0 0 0 0 0
> > 2 0xffff07ffbf290980 0 5 2.19% 4 2 2 14 14 0 0 0 0 0 10 1 1 0 2 0 0 0
> > 3 0xffffd976e57275c0 1 1 0.55% 1 1 0 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0
> > 4 0xffffd976e6071c00 1 3 0.55% 1 0 1 4 4 0 0 0 0 0 3 0 0 0 1 0 0 0
> > [snip]
> > =================================================
> > Shared Cache Line Distribution Pareto
> > =================================================
> > #
> > # -- Peer Snoop -- ------- Store Refs ------ --------- Data address --------- ---------- cycles ---------- Total cpu Shared
> > # Num Rmt Lcl L1 Hit L1 Miss N/A Offset Node PA cnt Code address rmt peer lcl peer load records cnt Symbol Object Source:Line Node
> > # ..... ....... ....... ....... ....... ....... .................. .... ...... .................. ........ ........ ........ ....... ........ .......................... ....... ......................... ....
> > #
> > ----------------------------------------------------------------------
> > 0 6 131 0 0 3038 0x422140
> > ----------------------------------------------------------------------
> > 0.00% 0.00% 0.00% 0.00% 52.60% 0x8 0 1 0x400e6c 0 0 0 1598 4 [.] writer tugtest tugtest.c:152 0 1
> > 0.00% 0.00% 0.00% 0.00% 47.40% 0x10 0 1 0x400e7c 0 0 0 1440 4 [.] writer tugtest tugtest.c:153 0 1
> > 33.33% 75.57% 0.00% 0.00% 0.00% 0x20 0 1 0x401018 4095 3803 3419 409 4 [.] reader tugtest tugtest.c:187 0 1
> > 66.67% 24.43% 0.00% 0.00% 0.00% 0x28 0 1 0x401034 4095 3470 3643 413 4 [.] reader tugtest tugtest.c:187 0 1
> >
> > ----------------------------------------------------------------------
> > 1 0 7 0 0 0 0xffffd976e63ae5c0
> > ----------------------------------------------------------------------
> > 0.00% 57.14% 0.00% 0.00% 0.00% 0x0 1 1 0xffffd976e4815fbc 0 1333 0 4 2 [k] ktime_get [kernel.kallsyms] seqlock.h:276 1
> > 0.00% 14.29% 0.00% 0.00% 0.00% 0x0 1 1 0xffffd976e4816d10 0 266 794 4 3 [k] ktime_get_update_offsets_n [kernel.kallsyms] seqlock.h:276 0 1
> > 0.00% 28.57% 0.00% 0.00% 0.00% 0x30 1 1 0xffffd976e4816d20 0 87 150 4 3 [k] ktime_get_update_offsets_n [kernel.kallsyms] timekeeping.c:2298 0 1
> >
> > ----------------------------------------------------------------------
> > 2 2 2 0 0 0 0xffff07ffbf290980
> > ----------------------------------------------------------------------
> > 50.00% 100.00% 0.00% 0.00% 0.00% 0x4 0 1 0xffffd976e47d2bdc 1217 1600 1147 4 3 [k] queued_spin_lock_slowpath [kernel.kallsyms] qspinlock.c:511 0 1
> > 50.00% 0.00% 0.00% 0.00% 0.00% 0x4 0 1 0xffffd976e47d2a2c 4033 0 0 1 1 [k] queued_spin_lock_slowpath [kernel.kallsyms] qspinlock.c:382 0 1
> >
> > ----------------------------------------------------------------------
> >
> > Thanks for doing this. It looks good.
>
> You are welcome! And very appreicate your helping to mature the code.
>
> > I'll assume someone else is reviewing your code changes.
>
> Yeah, let's give a bit more time for reviewing.
>
> Thanks,
> Leo
This is great Leo! I've not been able to test the changes but I didn't
have any coding comments (happy to give an Acked-by). Do you think we
can add a test for this? The test can skip when c2c isn't supported.
Thanks,
Ian