| Message ID | 1555419492-16906-1-git-send-email-magnus.karlsson@intel.com |
|---|---|
| Headers | show |
| Series | libbpf: remove two dependencies on Linux | expand |
On Tue, Apr 16, 2019 at 5:58 AM Magnus Karlsson <magnus.karlsson@intel.com> wrote: > > This patch set fixes one bug and removes two dependencies on Linux > kernel headers from the XDP socket code in libbpf. A number of people > have pointed out that these two dependencies make it hard to build the > XDP socket part of libbpf without any kernel header dependencies. The > two removed dependecies are: > > * Remove the usage of likely and unlikely (compiler.h) in xsk.h. It > has been reported that the use of these actually decreases the > performance of the ring access code due to an increase in > instruction cache misses, so let us just remove these. > > * Remove the dependency on barrier.h as it brings in a lot of kernel > headers. As the XDP socket code only uses two simple functions from > it, we can reimplement these. As a bonus, the new implementation is > faster as it uses the same barrier primitives as the kernel does > when the same code is compiled there. Without this patch, the user > land code uses lfence and sfence on x86, which are unnecessarily > harsh/thorough. > > In the process of removing these dependencies a missing barrier > function for at least PPC64 was discovered. For a full explanation on > the missing barrier, please refer to patch 1. So the patch set now > starts with two patches fixing this. I have also added a patch at the > end removing this full memory barrier for x86 only, as it is not > needed there. > > Structure of the patch set: > Patch 1-2: Adds the missing barrier function in kernel and user space. > Patch 3-4: Removes the dependencies > Patch 5: Optimizes the added barrier from patch 2 so that it does not > do unnecessary work on x86. > > v2 -> v3: > * Added missing memory barrier in ring code > * Added an explanation on the three barriers we use in the code > * Moved barrier functions from xsk.h to libbpf_util.h > * Added comment on why we have these functions in libbpf_util.h > * Added a new barrier function in user space that makes it possible to > remove the full memory barrier on x86. > > v1 -> v2: > * Added comment about validity of ARM 32-bit barriers. > Only armv7 and above. > > /Magnus > > Magnus Karlsson (5): > xsk: fix XDP socket ring buffer memory ordering > libbpf: fix XDP socket ring buffer memory ordering > libbpf: remove likely/unlikely in xsk.h > libbpf: remove dependency on barrier.h in xsk.h > libbpf: optimize barrier for XDP socket rings For the set: Acked-by: Song Liu <songliubraving@fb.com> > > net/xdp/xsk_queue.h | 56 +++++++++++++++++++++++++++++++++++++++++---- > tools/lib/bpf/libbpf_util.h | 30 ++++++++++++++++++++++++ > tools/lib/bpf/xsk.h | 22 +++++++++++++----- > 3 files changed, 98 insertions(+), 10 deletions(-) > > -- > 2.7.4
On Tue, Apr 16, 2019 at 5:58 AM Magnus Karlsson <magnus.karlsson@intel.com> wrote: > > This patch set fixes one bug and removes two dependencies on Linux > kernel headers from the XDP socket code in libbpf. A number of people > have pointed out that these two dependencies make it hard to build the > XDP socket part of libbpf without any kernel header dependencies. The > two removed dependecies are: > > * Remove the usage of likely and unlikely (compiler.h) in xsk.h. It > has been reported that the use of these actually decreases the > performance of the ring access code due to an increase in > instruction cache misses, so let us just remove these. > > * Remove the dependency on barrier.h as it brings in a lot of kernel > headers. As the XDP socket code only uses two simple functions from > it, we can reimplement these. As a bonus, the new implementation is > faster as it uses the same barrier primitives as the kernel does > when the same code is compiled there. Without this patch, the user > land code uses lfence and sfence on x86, which are unnecessarily > harsh/thorough. > > In the process of removing these dependencies a missing barrier > function for at least PPC64 was discovered. For a full explanation on > the missing barrier, please refer to patch 1. So the patch set now > starts with two patches fixing this. I have also added a patch at the > end removing this full memory barrier for x86 only, as it is not > needed there. > > Structure of the patch set: > Patch 1-2: Adds the missing barrier function in kernel and user space. > Patch 3-4: Removes the dependencies > Patch 5: Optimizes the added barrier from patch 2 so that it does not > do unnecessary work on x86. Applied. Thanks
This patch set fixes one bug and removes two dependencies on Linux kernel headers from the XDP socket code in libbpf. A number of people have pointed out that these two dependencies make it hard to build the XDP socket part of libbpf without any kernel header dependencies. The two removed dependecies are: * Remove the usage of likely and unlikely (compiler.h) in xsk.h. It has been reported that the use of these actually decreases the performance of the ring access code due to an increase in instruction cache misses, so let us just remove these. * Remove the dependency on barrier.h as it brings in a lot of kernel headers. As the XDP socket code only uses two simple functions from it, we can reimplement these. As a bonus, the new implementation is faster as it uses the same barrier primitives as the kernel does when the same code is compiled there. Without this patch, the user land code uses lfence and sfence on x86, which are unnecessarily harsh/thorough. In the process of removing these dependencies a missing barrier function for at least PPC64 was discovered. For a full explanation on the missing barrier, please refer to patch 1. So the patch set now starts with two patches fixing this. I have also added a patch at the end removing this full memory barrier for x86 only, as it is not needed there. Structure of the patch set: Patch 1-2: Adds the missing barrier function in kernel and user space. Patch 3-4: Removes the dependencies Patch 5: Optimizes the added barrier from patch 2 so that it does not do unnecessary work on x86. v2 -> v3: * Added missing memory barrier in ring code * Added an explanation on the three barriers we use in the code * Moved barrier functions from xsk.h to libbpf_util.h * Added comment on why we have these functions in libbpf_util.h * Added a new barrier function in user space that makes it possible to remove the full memory barrier on x86. v1 -> v2: * Added comment about validity of ARM 32-bit barriers. Only armv7 and above. /Magnus Magnus Karlsson (5): xsk: fix XDP socket ring buffer memory ordering libbpf: fix XDP socket ring buffer memory ordering libbpf: remove likely/unlikely in xsk.h libbpf: remove dependency on barrier.h in xsk.h libbpf: optimize barrier for XDP socket rings net/xdp/xsk_queue.h | 56 +++++++++++++++++++++++++++++++++++++++++---- tools/lib/bpf/libbpf_util.h | 30 ++++++++++++++++++++++++ tools/lib/bpf/xsk.h | 22 +++++++++++++----- 3 files changed, 98 insertions(+), 10 deletions(-) -- 2.7.4