On Thu 24 Jan 2019 at 17:21, Dennis Zhou <den...@kernel.org> wrote:
> Hi Vlad and Eric,
>
> On Tue, Jan 22, 2019 at 09:33:10AM -0800, Eric Dumazet wrote:
>> On Mon, Jan 21, 2019 at 3:24 AM Vlad Buslov <vla...@mellanox.com> wrote:
>> >
>> > Hi Eric,
>> >
>> > I've been investigating significant tc filter insertion rate degradation
>> > and it seems it is caused by your commit 001c96db0181 ("net: align
>> > gnet_stats_basic_cpu struct"). With this commit insertion rate is
>> > reduced from ~65k rules/sec to ~43k rules/sec when inserting 1m rules
>> > from file in tc batch mode on my machine.
>> >
>> > Tc perf profile indicates that pcpu allocator now consumes 2x CPU:
>> >
>> > 1) Before:
>> >
>> > Samples: 63K of event 'cycles:ppp', Event count (approx.): 48796480071
>> > Children Self Co Shared Object Symbol
>> > + 21.19% 3.38% tc [kernel.vmlinux] [k] pcpu_alloc
>> > + 3.45% 0.25% tc [kernel.vmlinux] [k] pcpu_alloc_area
>> >
>> > 2) After:
>> >
>> > Samples1: 92K of event 'cycles:ppp', Event count (approx.): 71446806550
>> > Children Self Co Shared Object Symbol
>> > + 44.67% 3.99% tc [kernel.vmlinux] [k] pcpu_alloc
>> > + 19.25% 0.22% tc [kernel.vmlinux] [k] pcpu_alloc_area
>> >
>> > It seems that it takes much more work for pcpu allocator to perform
>> > allocation with new stricter alignment requirements. Not sure if it is
>> > expected behavior or not in this case.
>> >
>> > Regards,
>> > Vlad
>
> Would you mind sharing a little more information with me:
> 1) output before and after a run of /sys/kernel/debug/percpu_stats
Hi Dennis,
Some of these files are quite large, so I put them to my Dropbox.
Output before:
Percpu Memory Statistics
Allocation Info:
----------------------------------------
unit_size : 262144
static_size : 139160
reserved_size : 8192
dyn_size : 28776
atom_size : 2097152
alloc_size : 2097152
Global Stats:
----------------------------------------
nr_alloc : 3343
nr_dealloc : 752
nr_cur_alloc : 2591
nr_max_alloc : 2598
nr_chunks : 3
nr_max_chunks : 3
min_alloc_size : 4
max_alloc_size : 8208
empty_pop_pages : 3
Per Chunk Stats:
----------------------------------------
Chunk: <- Reserved Chunk
nr_alloc : 5
max_alloc_size : 320
empty_pop_pages : 0
first_bit : 1002
free_bytes : 7448
contig_bytes : 7424
sum_frag : 24
max_frag : 24
cur_min_alloc : 16
cur_med_alloc : 64
cur_max_alloc : 320
Chunk: <- First Chunk
nr_alloc : 479
max_alloc_size : 8208
empty_pop_pages : 0
first_bit : 8192
free_bytes : 0
contig_bytes : 0
sum_frag : 0
max_frag : 0
cur_min_alloc : 4
cur_med_alloc : 24
cur_max_alloc : 8208
Chunk:
nr_alloc : 1925
max_alloc_size : 8208
empty_pop_pages : 0
first_bit : 63102
free_bytes : 852
contig_bytes : 12
sum_frag : 852
max_frag : 12
cur_min_alloc : 4
cur_med_alloc : 8
cur_max_alloc : 8208
Chunk:
nr_alloc : 182
max_alloc_size : 936
empty_pop_pages : 3
first_bit : 21
free_bytes : 256452
contig_bytes : 255120
sum_frag : 1332
max_frag : 368
cur_min_alloc : 8
cur_med_alloc : 20
cur_max_alloc : 320
After: https://www.dropbox.com/s/unyzhx4vgo2x30e/stats_after?dl=0
> 2) a full perf output
https://www.dropbox.com/s/isfcxca3npn5slx/perf.data?dl=0
> 3) a reproducer
$ sudo tc -b add.0
Example batch file: https://www.dropbox.com/s/ey7cbl5nwu5p0tg/add.0?dl=0
Thanks,
Vlad
