| Message ID | 20210924025450.4138503-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 804bccba71a57e7e5deb507a4c8ebbab730909c0 |
| Headers | show |
| Series | sched: task_struct: Fill unconditional hole induced by sched_entity | expand |
On Thu, Sep 23, 2021 at 07:54:50PM -0700, Kees Cook wrote: > With struct sched_entity before the other sched entities, its alignment > won't induce a struct hole. This saves 64 bytes in defconfig task_struct: Friendly ping. Can someone snag this for -tip please? Thanks! -Kees > > Before: > ... > unsigned int rt_priority; /* 120 4 */ > > /* XXX 4 bytes hole, try to pack */ > > /* --- cacheline 2 boundary (128 bytes) --- */ > const struct sched_class * sched_class; /* 128 8 */ > > /* XXX 56 bytes hole, try to pack */ > > /* --- cacheline 3 boundary (192 bytes) --- */ > struct sched_entity se __attribute__((__aligned__(64))); /* 192 448 */ > /* --- cacheline 10 boundary (640 bytes) --- */ > struct sched_rt_entity rt; /* 640 48 */ > struct sched_dl_entity dl __attribute__((__aligned__(8))); /* 688 224 */ > /* --- cacheline 14 boundary (896 bytes) was 16 bytes ago --- */ > > After: > ... > unsigned int rt_priority; /* 120 4 */ > > /* XXX 4 bytes hole, try to pack */ > > /* --- cacheline 2 boundary (128 bytes) --- */ > struct sched_entity se __attribute__((__aligned__(64))); /* 128 448 */ > /* --- cacheline 9 boundary (576 bytes) --- */ > struct sched_rt_entity rt; /* 576 48 */ > struct sched_dl_entity dl __attribute__((__aligned__(8))); /* 624 224 */ > /* --- cacheline 13 boundary (832 bytes) was 16 bytes ago --- */ > > Summary diff: > - /* size: 7040, cachelines: 110, members: 188 */ > + /* size: 6976, cachelines: 109, members: 188 */ > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > include/linux/sched.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 39039ce8ac4c..27ed1d40028f 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -775,10 +775,10 @@ struct task_struct { > int normal_prio; > unsigned int rt_priority; > > - const struct sched_class *sched_class; > struct sched_entity se; > struct sched_rt_entity rt; > struct sched_dl_entity dl; > + const struct sched_class *sched_class; > > #ifdef CONFIG_SCHED_CORE > struct rb_node core_node; > -- > 2.30.2 >
On Tue, Oct 05, 2021 at 09:48:51PM -0700, Kees Cook wrote: > On Thu, Sep 23, 2021 at 07:54:50PM -0700, Kees Cook wrote: > > With struct sched_entity before the other sched entities, its alignment > > won't induce a struct hole. This saves 64 bytes in defconfig task_struct: > > Friendly ping. Can someone snag this for -tip please? Hurpmf... if only we had like perf driven pahole output :/ Picked it up, we'll see what if anything hurts.
On Wed, Oct 06, 2021 at 11:27:03AM +0200, Peter Zijlstra wrote: > On Tue, Oct 05, 2021 at 09:48:51PM -0700, Kees Cook wrote: > > On Thu, Sep 23, 2021 at 07:54:50PM -0700, Kees Cook wrote: > > > With struct sched_entity before the other sched entities, its alignment > > > won't induce a struct hole. This saves 64 bytes in defconfig task_struct: > > > > Friendly ping. Can someone snag this for -tip please? > > Hurpmf... if only we had like perf driven pahole output :/ Normally I wouldn't even make suggestions in task_struct given the high variability due to CONFIG options, but this case was pretty universal. > Picked it up, we'll see what if anything hurts. Thanks! *fingers crossed*
diff --git a/include/linux/sched.h b/include/linux/sched.h index 39039ce8ac4c..27ed1d40028f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -775,10 +775,10 @@ struct task_struct { int normal_prio; unsigned int rt_priority; - const struct sched_class *sched_class; struct sched_entity se; struct sched_rt_entity rt; struct sched_dl_entity dl; + const struct sched_class *sched_class; #ifdef CONFIG_SCHED_CORE struct rb_node core_node;
With struct sched_entity before the other sched entities, its alignment won't induce a struct hole. This saves 64 bytes in defconfig task_struct: Before: ... unsigned int rt_priority; /* 120 4 */ /* XXX 4 bytes hole, try to pack */ /* --- cacheline 2 boundary (128 bytes) --- */ const struct sched_class * sched_class; /* 128 8 */ /* XXX 56 bytes hole, try to pack */ /* --- cacheline 3 boundary (192 bytes) --- */ struct sched_entity se __attribute__((__aligned__(64))); /* 192 448 */ /* --- cacheline 10 boundary (640 bytes) --- */ struct sched_rt_entity rt; /* 640 48 */ struct sched_dl_entity dl __attribute__((__aligned__(8))); /* 688 224 */ /* --- cacheline 14 boundary (896 bytes) was 16 bytes ago --- */ After: ... unsigned int rt_priority; /* 120 4 */ /* XXX 4 bytes hole, try to pack */ /* --- cacheline 2 boundary (128 bytes) --- */ struct sched_entity se __attribute__((__aligned__(64))); /* 128 448 */ /* --- cacheline 9 boundary (576 bytes) --- */ struct sched_rt_entity rt; /* 576 48 */ struct sched_dl_entity dl __attribute__((__aligned__(8))); /* 624 224 */ /* --- cacheline 13 boundary (832 bytes) was 16 bytes ago --- */ Summary diff: - /* size: 7040, cachelines: 110, members: 188 */ + /* size: 6976, cachelines: 109, members: 188 */ Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)