| Message ID | 20230511012604.3222-1-zhang_fei_0403@163.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | RISC-V: Optimize memset for data sizes less than 16 bytes | expand |
On Thu, May 11, 2023 at 09:26:04AM +0800, zhangfei wrote: > From: zhangfei <zhangfei@nj.iscas.ac.cn> > > At present, the implementation of the memset function uses byte by byte storage > when processing tail data or when the initial data size is less than 16 bytes. > This approach is not efficient. Therefore, I filled head and tail with minimal > branching. Each conditional ensures that all the subsequently used offsets are > well-defined and in the dest region. Although this approach may result in > redundant storage, compared to byte by byte storage, it allows storage instructions > to be executed in parallel, reduces the number of jumps, and ultimately achieves > performance improvement. > > I used the code linked below for performance testing and commented on the memset > that calls the arm architecture in the code to ensure it runs properly on the > risc-v platform. > > [1] https://github.com/ARM-software/optimized-routines/blob/master/string/bench/memset.c#L53 > > The testing platform selected RISC-V SiFive U74.The test data is as follows: > > Before optimization > --------------------- > Random memset (bytes/ns): > memset_call 32K:0.45 64K:0.35 128K:0.30 256K:0.28 512K:0.27 1024K:0.25 avg 0.30 > > Medium memset (bytes/ns): > memset_call 8B:0.18 16B:0.48 32B:0.91 64B:1.63 128B:2.71 256B:4.40 512B:5.67 > Large memset (bytes/ns): > memset_call 1K:6.62 2K:7.02 4K:7.46 8K:7.70 16K:7.82 32K:7.63 64K:1.40 > > After optimization > --------------------- > Random memset bytes/ns): > memset_call 32K:0.46 64K:0.35 128K:0.30 256K:0.28 512K:0.27 1024K:0.25 avg 0.31 > Medium memset (bytes/ns ) > memset_call 8B:0.27 16B:0.48 32B:0.91 64B:1.64 128B:2.71 256B:4.40 512B:5.67 > Large memset (bytes/ns): > memset_call 1K:6.62 2K:7.02 4K:7.47 8K:7.71 16K:7.83 32K:7.63 64K:1.40 > > From the results, it can be seen that memset has significantly improved its performance with > a data volume of around 8B, from 0.18 bytes/ns to 0.27 bytes/ns. > > The previous work was as follows: > 1. "[PATCH] riscv: Optimize memset" > 6d1cbe2e.3c31d.187eb14d990.Coremail.zhangfei@nj.iscas.ac.cn Cover letters should have a changelog, in this case a couple phrases stating what's different in v2 vs. v1. Thanks, drew > > Thanks, > Fei Zhang > > Andrew Jones (1): > RISC-V: lib: Improve memset assembler formatting > > arch/riscv/lib/memset.S | 143 ++++++++++++++++++++-------------------- > 1 file changed, 72 insertions(+), 71 deletions(-) > > zhangfei (1): > RISC-V: lib: Optimize memset performance > > arch/riscv/lib/memset.S | 40 +++++++++++++++++++++++++++++++++++++--- > 1 file changed, 37 insertions(+), 3 deletions(-) >
From: zhangfei <zhangfei@nj.iscas.ac.cn> At present, the implementation of the memset function uses byte by byte storage when processing tail data or when the initial data size is less than 16 bytes. This approach is not efficient. Therefore, I filled head and tail with minimal branching. Each conditional ensures that all the subsequently used offsets are well-defined and in the dest region. Although this approach may result in redundant storage, compared to byte by byte storage, it allows storage instructions to be executed in parallel, reduces the number of jumps, and ultimately achieves performance improvement. I used the code linked below for performance testing and commented on the memset that calls the arm architecture in the code to ensure it runs properly on the risc-v platform. [1] https://github.com/ARM-software/optimized-routines/blob/master/string/bench/memset.c#L53 The testing platform selected RISC-V SiFive U74.The test data is as follows: Before optimization --------------------- Random memset (bytes/ns): memset_call 32K:0.45 64K:0.35 128K:0.30 256K:0.28 512K:0.27 1024K:0.25 avg 0.30 Medium memset (bytes/ns): memset_call 8B:0.18 16B:0.48 32B:0.91 64B:1.63 128B:2.71 256B:4.40 512B:5.67 Large memset (bytes/ns): memset_call 1K:6.62 2K:7.02 4K:7.46 8K:7.70 16K:7.82 32K:7.63 64K:1.40 After optimization --------------------- Random memset bytes/ns): memset_call 32K:0.46 64K:0.35 128K:0.30 256K:0.28 512K:0.27 1024K:0.25 avg 0.31 Medium memset (bytes/ns ) memset_call 8B:0.27 16B:0.48 32B:0.91 64B:1.64 128B:2.71 256B:4.40 512B:5.67 Large memset (bytes/ns): memset_call 1K:6.62 2K:7.02 4K:7.47 8K:7.71 16K:7.83 32K:7.63 64K:1.40 From the results, it can be seen that memset has significantly improved its performance with a data volume of around 8B, from 0.18 bytes/ns to 0.27 bytes/ns. The previous work was as follows: 1. "[PATCH] riscv: Optimize memset" 6d1cbe2e.3c31d.187eb14d990.Coremail.zhangfei@nj.iscas.ac.cn Thanks, Fei Zhang Andrew Jones (1): RISC-V: lib: Improve memset assembler formatting arch/riscv/lib/memset.S | 143 ++++++++++++++++++++-------------------- 1 file changed, 72 insertions(+), 71 deletions(-) zhangfei (1): RISC-V: lib: Optimize memset performance arch/riscv/lib/memset.S | 40 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 37 insertions(+), 3 deletions(-)