> -----Original Message-----
> From: Christoph Hellwig [mailto:[email protected]]
> Sent: Friday, February 5, 2021 11:36 PM
> To: Song Bao Hua (Barry Song) <[email protected]>
> Cc: Christoph Hellwig <[email protected]>; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected]
> Subject: Re: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
>
> On Fri, Feb 05, 2021 at 10:32:26AM +0000, Song Bao Hua (Barry Song) wrote:
> > I can keep the struct size unchanged by changing the struct to
> >
> > struct map_benchmark {
> > __u64 avg_map_100ns; /* average map latency in 100ns */
> > __u64 map_stddev; /* standard deviation of map latency */
> > __u64 avg_unmap_100ns; /* as above */
> > __u64 unmap_stddev;
> > __u32 threads; /* how many threads will do map/unmap in parallel */
> > __u32 seconds; /* how long the test will last */
> > __s32 node; /* which numa node this benchmark will run on */
> > __u32 dma_bits; /* DMA addressing capability */
> > __u32 dma_dir; /* DMA data direction */
> > __u32 dma_trans_ns; /* time for DMA transmission in ns */
> >
> > __u32 exp; /* For future use */
> > __u64 expansion[9]; /* For future use */
> > };
> >
> > But the code is really ugly now.
>
> Thats why we usually use __u8 fields for reserved field. You might
> consider just switching to that instead while you're at it. I guess
> we'll just have to get the addition into 5.11 then to make sure we
> don't release a kernel with the alignment fix.
I assume there is no need to keep the same size with 5.11-rc, so
could change the struct to:
struct map_benchmark {
__u64 avg_map_100ns; /* average map latency in 100ns */
__u64 map_stddev; /* standard deviation of map latency */
__u64 avg_unmap_100ns; /* as above */
__u64 unmap_stddev;
__u32 threads; /* how many threads will do map/unmap in parallel */
__u32 seconds; /* how long the test will last */
__s32 node; /* which numa node this benchmark will run on */
__u32 dma_bits; /* DMA addressing capability */
__u32 dma_dir; /* DMA data direction */
__u8 expansion[84]; /* For future use */
};
This won't increase size on 64bit system, but it increases 4bytes
on 32bits system comparing to 5.11-rc. How do you think about it?
Thanks
Barry
