lkml.org 
[lkml]   [2020]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2 bpf] bpf: Do not grab the bucket spinlock by default on htab batch ops
From
Date


On 2/18/20 9:25 AM, Brian Vazquez wrote:
> Grabbing the spinlock for every bucket even if it's empty, was causing
> significant perfomance cost when traversing htab maps that have only a
> few entries. This patch addresses the issue by checking first the
> bucket_cnt, if the bucket has some entries then we go and grab the
> spinlock and proceed with the batching.
>
> Tested with a htab of size 50K and different value of populated entries.
>
> Before:
> Benchmark Time(ns) CPU(ns)
> ---------------------------------------------
> BM_DumpHashMap/1 2759655 2752033
> BM_DumpHashMap/10 2933722 2930825
> BM_DumpHashMap/200 3171680 3170265
> BM_DumpHashMap/500 3639607 3635511
> BM_DumpHashMap/1000 4369008 4364981
> BM_DumpHashMap/5k 11171919 11134028
> BM_DumpHashMap/20k 69150080 69033496
> BM_DumpHashMap/39k 190501036 190226162
>
> After:
> Benchmark Time(ns) CPU(ns)
> ---------------------------------------------
> BM_DumpHashMap/1 202707 200109
> BM_DumpHashMap/10 213441 210569
> BM_DumpHashMap/200 478641 472350
> BM_DumpHashMap/500 980061 967102
> BM_DumpHashMap/1000 1863835 1839575
> BM_DumpHashMap/5k 8961836 8902540
> BM_DumpHashMap/20k 69761497 69322756
> BM_DumpHashMap/39k 187437830 186551111
>
> Fixes: 057996380a42 ("bpf: Add batch ops to all htab bpf map")
> Cc: Yonghong Song <yhs@fb.com>
> Signed-off-by: Brian Vazquez <brianvv@google.com>

Thanks for the fix.
Acked-by: Yonghong Song <yhs@fb.com>

> ---
> v1 -> v2: Skip hlist_nulls_for_each_entry_safe if lock is not held
>
> kernel/bpf/hashtab.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)

\
 
 \ /
  Last update: 2020-02-18 22:25    [W:0.092 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site