| Message ID | 1419002899-17314-1-git-send-email-petri.savolainen@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Fri, Dec 19, 2014 at 9:28 AM, Petri Savolainen < petri.savolainen@linaro.org> wrote: > > Buf_size parameter defines minimum buffer/segment length. > Use 0 for default length. > > Signed-off-by: Petri Savolainen <petri.savolainen@linaro.org> > --- > .../linux-generic/include/api/odp_buffer_pool.h | 21 > +++++++++++---------- > 1 file changed, 11 insertions(+), 10 deletions(-) > > diff --git a/platform/linux-generic/include/api/odp_buffer_pool.h > b/platform/linux-generic/include/api/odp_buffer_pool.h > index 4da5f84..27e816d 100644 > --- a/platform/linux-generic/include/api/odp_buffer_pool.h > +++ b/platform/linux-generic/include/api/odp_buffer_pool.h > @@ -35,18 +35,19 @@ extern "C" { > /** > * Buffer pool parameters > * Used to communicate buffer pool creation options. > + * > + * @see ODP_CONFIG_PACKET_BUF_LEN_MIN, ODP_CONFIG_BUFFER_ALIGN_MIN, > + * ODP_CONFIG_BUFFER_ALIGN_MAX > */ > typedef struct odp_buffer_pool_param_t { > - uint32_t buf_size; /**< Buffer size in bytes. The maximum > - number of bytes application will > - store in each buffer. For packets, this > - is the maximum packet data length, and > - configured headroom and tailroom will be > - added to this number */ > - uint32_t buf_align; /**< Minimum buffer alignment in bytes. > - Valid values are powers of two. Use 0 > - for default alignment. Default will > - always be a multiple of 8. */ > + uint32_t buf_size; /**< Minimum buffer length in bytes. For > packets, > + this is the minimum segment buffer > length. The > + length includes head-/tailroom bytes. Use > 0 for > + default length. */ > This is confusing. Presumably for buffers of type ODP_BUFFER_TYPE_PACKET this is a synonym for ODP_CONFIG_PACKET_BUF_LEN_MIN. However, how is a 0 value to be interpreted for other buffer types? Need to specify that here. In the current code it is legitimate to specify a buf_size of zero as that means that buffers will consist only of metadata. Buffers of type ODP_BUFFER_TYPE_TIMEOUT fall into that category, for example. Since this is a buffer structure, not a packet structure, the documentation should reflect that. Beyond this, as we discussed yesterday, a portable application really has no idea what segment sizes are being used by the underlying implementation, nor should it care. The only application-observable impact of segmentation is on packet addressability. As written, this spec precludes an SoC that has fixed-sized HW-managed segments from being ODP compliant. You've argued that an implementation can restrict acceptable values for this parameter but then the application is just echoing back the ODP_CONFIG variables here, so what is the point of this variable? The purpose of buf_size and num_bufs is to allow the implementation to calculate the amount of storage it needs to reserve to support the buffer pool. So if an application says "I want N buffers of maximum size S" that makes sense. Saying "I want N things that will be divided into some unspecified number of segments of size S" is ambiguous because N is no longer determinate (this was one of the design issues with the original buffer pool implementation). So if num_bufs is no longer determinate, what is it's purpose? > + uint32_t buf_align; /**< Minimum buffer alignment in bytes. Valid > values > + are powers of two. Use 0 for default > + alignment. Default will always be a > multiple > + of 8. */ > uint32_t num_bufs; /**< Number of buffers in the pool */ > int buf_type; /**< Buffer type */ > } odp_buffer_pool_param_t; > -- > 2.2.1 > > > _______________________________________________ > lng-odp mailing list > lng-odp@lists.linaro.org > http://lists.linaro.org/mailman/listinfo/lng-odp >
diff --git a/platform/linux-generic/include/api/odp_buffer_pool.h b/platform/linux-generic/include/api/odp_buffer_pool.h index 4da5f84..27e816d 100644 --- a/platform/linux-generic/include/api/odp_buffer_pool.h +++ b/platform/linux-generic/include/api/odp_buffer_pool.h @@ -35,18 +35,19 @@ extern "C" { /** * Buffer pool parameters * Used to communicate buffer pool creation options. + * + * @see ODP_CONFIG_PACKET_BUF_LEN_MIN, ODP_CONFIG_BUFFER_ALIGN_MIN, + * ODP_CONFIG_BUFFER_ALIGN_MAX */ typedef struct odp_buffer_pool_param_t { - uint32_t buf_size; /**< Buffer size in bytes. The maximum - number of bytes application will - store in each buffer. For packets, this - is the maximum packet data length, and - configured headroom and tailroom will be - added to this number */ - uint32_t buf_align; /**< Minimum buffer alignment in bytes. - Valid values are powers of two. Use 0 - for default alignment. Default will - always be a multiple of 8. */ + uint32_t buf_size; /**< Minimum buffer length in bytes. For packets, + this is the minimum segment buffer length. The + length includes head-/tailroom bytes. Use 0 for + default length. */ + uint32_t buf_align; /**< Minimum buffer alignment in bytes. Valid values + are powers of two. Use 0 for default + alignment. Default will always be a multiple + of 8. */ uint32_t num_bufs; /**< Number of buffers in the pool */ int buf_type; /**< Buffer type */ } odp_buffer_pool_param_t;
Buf_size parameter defines minimum buffer/segment length. Use 0 for default length. Signed-off-by: Petri Savolainen <petri.savolainen@linaro.org> --- .../linux-generic/include/api/odp_buffer_pool.h | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)