Messages in this thread Patch in this message | | | Date | Thu, 25 Mar 2021 09:57:29 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 1/2] perf/core: Share an event with multiple cgroups |
| |
Em Thu, Mar 25, 2021 at 12:55:50AM +0000, Song Liu escreveu: > > On Mar 23, 2021, at 9:21 AM, Namhyung Kim <namhyung@kernel.org> wrote: > > #ifdef CONFIG_SECURITY > > @@ -780,6 +792,14 @@ struct perf_event { > > #endif /* CONFIG_PERF_EVENTS */ > > };
> > +struct perf_cgroup_node { > > + struct hlist_node node; > > + u64 id; > > + u64 count; > > + u64 time_enabled; > > + u64 time_running; > > + u64 padding[2]; > > Do we really need the padding? For cache line alignment?
I guess so, to get it to 64 bytes, then having it as:
struct perf_cgroup_node { struct hlist_node node; u64 id; u64 count; u64 time_enabled; u64 time_running; } ____cacheline_aligned;
Seems better :-)
Testing:
[acme@five c]$ cat cacheline_aligned.c #ifndef ____cacheline_aligned #define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES))) #endif // from ../build/v5.12.0-rc4+/include/generated/autoconf.h #define CONFIG_X86_L1_CACHE_SHIFT 6
#define L1_CACHE_SHIFT (CONFIG_X86_L1_CACHE_SHIFT) #define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
#ifndef SMP_CACHE_BYTES #define SMP_CACHE_BYTES L1_CACHE_BYTES #endif
typedef long long unsigned int u64;
struct hlist_node { struct hlist_node * next; /* 0 8 */ struct hlist_node * * pprev; /* 8 8 */ /* size: 16, cachelines: 1, members: 2 */ /* last cacheline: 16 bytes */ }; struct perf_cgroup_node { struct hlist_node node; u64 id; u64 count; u64 time_enabled; u64 time_running; } ____cacheline_aligned foo; [acme@five c]$ cc -g -c -o cacheline_aligned.o cacheline_aligned.c [acme@five c]$ pahole cacheline_aligned.o struct hlist_node { struct hlist_node * next; /* 0 8 */ struct hlist_node * * pprev; /* 8 8 */ /* size: 16, cachelines: 1, members: 2 */ /* last cacheline: 16 bytes */ }; struct perf_cgroup_node { struct hlist_node node; /* 0 16 */ u64 id; /* 16 8 */ u64 count; /* 24 8 */ u64 time_enabled; /* 32 8 */ u64 time_running; /* 40 8 */ /* size: 64, cachelines: 1, members: 5 */ /* padding: 16 */ } __attribute__((__aligned__(64))); [acme@five c]$ - Arnaldo
| |