On Tue, 2024-06-25 at 22:09 +0800, Huacai Chen wrote: > On Tue, Jun 25, 2024 at 7:01 PM Mateusz Guzik <mjguzik@xxxxxxxxx> > wrote: > > > > The newly used helper also checks for 0-sized buffers. > > > > This avoids path lookup code, lockref management, memory allocation > > and > > in case of NULL path userspace memory access (which can be quite > > expensive with SMAP on x86_64). > > > > statx with AT_EMPTY_PATH paired with "" or NULL argument as > > appropriate > > issued on Sapphire Rapids (ops/s): > > stock: 4231237 > > 0-check: 5944063 (+40%) > > NULL path: 6601619 (+11%/+56%) > > > > Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx> > Hi, Ruoyao, > > I'm a bit confused. Ii this patch a replacement of your recent patch? Yes, both Linus and Christian hates introducing a new AT_ flag for this. This patch just makes statx(fd, NULL, AT_EMPTY_PATH, ...) behave like statx(fd, "", AT_EMPTY_PATH, ...) instead. NULL avoids the performance issue and it's also audit-able by seccomp BPF. -- Xi Ruoyao <xry111@xxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
