Hi maintainers, A gentle ping.
Thanks, Shaokun On 2020/4/30 11:25, Shaokun Zhang wrote: > From: Yuqi Jin <[email protected]> > > __fget_files does check the @f_mode with mask variable and will do some > atomic operations on @f_count while both are on the same cacheline. > Many CPU cores do file access and it will cause much conflicts on @f_count. > If we could make the two members into different cachelines, it shall relax > the siutations. > > We have tested this on ARM64 and X86, the result is as follows: > > Syscall of unixbench has been run on Huawei Kunpeng920 with this patch: > 24 x System Call Overhead 1 > > System Call Overhead 3160841.4 lps (10.0 s, 1 samples) > > System Benchmarks Partial Index BASELINE RESULT INDEX > System Call Overhead 15000.0 3160841.4 2107.2 > ======== > System Benchmarks Index Score (Partial Only) 2107.2 > > Without this patch: > 24 x System Call Overhead 1 > > System Call Overhead 2222456.0 lps (10.0 s, 1 samples) > > System Benchmarks Partial Index BASELINE RESULT INDEX > System Call Overhead 15000.0 2222456.0 1481.6 > ======== > System Benchmarks Index Score (Partial Only) 1481.6 > > And on Intel 6248 platform with this patch: > 40 CPUs in system; running 24 parallel copies of tests > > System Call Overhead 4288509.1 lps (10.0 s, 1 > samples) > > System Benchmarks Partial Index BASELINE RESULT INDEX > System Call Overhead 15000.0 4288509.1 2859.0 > ======== > System Benchmarks Index Score (Partial Only) 2859.0 > > Without this patch: > 40 CPUs in system; running 24 parallel copies of tests > > System Call Overhead 3666313.0 lps (10.0 s, 1 > samples) > > System Benchmarks Partial Index BASELINE RESULT INDEX > System Call Overhead 15000.0 3666313.0 2444.2 > ======== > System Benchmarks Index Score (Partial Only) 2444.2 > > Cc: Alexander Viro <[email protected]> > Signed-off-by: Yuqi Jin <[email protected]> > Signed-off-by: Shaokun Zhang <[email protected]> > --- > include/linux/fs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 4f6f59b4f22a..90e76283f0fd 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -953,7 +953,6 @@ struct file { > */ > spinlock_t f_lock; > enum rw_hint f_write_hint; > - atomic_long_t f_count; > unsigned int f_flags; > fmode_t f_mode; > struct mutex f_pos_lock; > @@ -976,6 +975,7 @@ struct file { > #endif /* #ifdef CONFIG_EPOLL */ > struct address_space *f_mapping; > errseq_t f_wb_err; > + atomic_long_t f_count; > } __randomize_layout > __attribute__((aligned(4))); /* lest something weird decides that 2 > is OK */ > >
