Re: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
On Fri, Feb 05, 2021 at 10:52:37AM +, Song Bao Hua (Barry Song) wrote:
> 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?
Yes, that sounds good. Please send me a two patch series with the
first one changing the alignment, and the second adding the delay.
I'll send the first one off to Linus ASAP then.
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RE: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
> -Original Message-
> From: Christoph Hellwig [mailto:h...@lst.de]
> Sent: Friday, February 5, 2021 11:36 PM
> To: Song Bao Hua (Barry Song)
> Cc: Christoph Hellwig ; m.szyprow...@samsung.com;
> robin.mur...@arm.com; iommu@lists.linux-foundation.org;
> linux-ker...@vger.kernel.org; linux...@openeuler.org
> Subject: Re: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
>
> On Fri, Feb 05, 2021 at 10:32:26AM +, 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
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Re: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
On Fri, Feb 05, 2021 at 10:32:26AM +, 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.
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RE: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
> -Original Message-
> From: Christoph Hellwig [mailto:h...@lst.de]
> Sent: Friday, February 5, 2021 10:21 PM
> To: Song Bao Hua (Barry Song)
> Cc: m.szyprow...@samsung.com; h...@lst.de; robin.mur...@arm.com;
> iommu@lists.linux-foundation.org; linux-ker...@vger.kernel.org;
> linux...@openeuler.org
> Subject: Re: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
>
> On Fri, Feb 05, 2021 at 03:00:35PM +1300, Barry Song wrote:
> > + __u32 dma_trans_ns; /* time for DMA transmission in ns */
> > __u64 expansion[10];/* For future use */
>
> We need to keep the struct size, so the expansion field needs to
> shrink by the equivalent amount of data that is added in dma_trans_ns.
Unfortunately I didn't put a rsv u32 field after dma_dir
in the original patch.
There were five 32bits data before expansion[]:
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 */
__u64 expansion[10];/* For future use */
};
My bad. That was really silly. I should have done the below from
the first beginning:
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 rsv;
__u64 expansion[10];/* For future use */
};
So on 64bit system, this patch doesn't change the length of struct
as the new added u32 just fill the gap between dma_dir and expansion.
For 32bit system, this patch increases 4 bytes in the length.
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.
Thanks
Barry
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Re: [PATCH v2] dma-mapping: benchmark: pretend DMA is transmitting
On Fri, Feb 05, 2021 at 03:00:35PM +1300, Barry Song wrote: > + __u32 dma_trans_ns; /* time for DMA transmission in ns */ > __u64 expansion[10];/* For future use */ We need to keep the struct size, so the expansion field needs to shrink by the equivalent amount of data that is added in dma_trans_ns. ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
