Re: CONFIG_PACKET_MMAP help
Hello!
> 1. for tp_frame_size, I dont want to truncate any data on ethernet, I
> need 1514 bytes, is this the best way to do it and not waste space?
To select small snapsize (obtained from later experiments),
to set PACKET_COPY_THRESH to read larger packets via recvmsg().
> 2. what is tp_block_nr for? I dont understand it, I just set it to 1
> and make tp_block_size big enough for all the frames I need, so its
> just one contiguous space, all I need is about a megabyte I think.
Kernel has problems with allocating large chunks of memory.
If you see problems with allocating large chuns, split them
to less ones.
> while(1) {
>if (tp->status == 0) poll() for pollin on the socket /* is there a
>race here? */
No. poll returns, when new frame appears.
> 4. what does the copy threshold setsockopt tuning accomplish? doesnt it always
> have to copy anyway, to the mmaped area?
see anser to question 1. It has a sense when size of chunk is small enough.
Small packets are copied to ring, large ones (which are truncated) are queued
to socket to be received via recvmsg().
Alexey
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Re: CONFIG_PACKET_MMAP help
Hello!
1. for tp_frame_size, I dont want to truncate any data on ethernet, I
need 1514 bytes, is this the best way to do it and not waste space?
To select small snapsize (obtained from later experiments),
to set PACKET_COPY_THRESH to read larger packets via recvmsg().
2. what is tp_block_nr for? I dont understand it, I just set it to 1
and make tp_block_size big enough for all the frames I need, so its
just one contiguous space, all I need is about a megabyte I think.
Kernel has problems with allocating large chunks of memory.
If you see problems with allocating large chuns, split them
to less ones.
while(1) {
if (tp-status == 0) poll() for pollin on the socket /* is there a
race here? */
No. poll returns, when new frame appears.
4. what does the copy threshold setsockopt tuning accomplish? doesnt it always
have to copy anyway, to the mmaped area?
see anser to question 1. It has a sense when size of chunk is small enough.
Small packets are copied to ring, large ones (which are truncated) are queued
to socket to be received via recvmsg().
Alexey
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: CONFIG_PACKET_MMAP help
Hi, [EMAIL PROTECTED] wrote: > > 1. for tp_frame_size, I dont want to truncate any data on ethernet, I > need 1514 bytes, is this the best way to do it and not waste space? > > static const int TURBO_FRAME_SIZE= > TPACKET_ALIGN(TPACKET_ALIGN(sizeof(tpacket_hdr)) + >TPACKET_ALIGN(sizeof(struct sockaddr_ll)+ETH_HLEN) + 1500); Looks OK. Maybe instead of ETH_HLEN min(ETH_HLEN,16)? The framesize calculation is really strange... > 2. what is tp_block_nr for? I dont understand it, I just set it to 1 > and make tp_block_size big enough for all the frames I need, so its > just one contiguous space, all I need is about a megabyte I think. Better go the other way around - set tb_block_size to PAGE_SIZE and tb_block_nr appropriate. tb_block_size is the contiguous physical memory the kernel tries to allocate. Anything above PAGE_SIZE is likely to fail. For you that would mean only 2 packets per 4k-page. You could try to start with bigger (power of 2) block sizes and go down to smaller ones if it fails (ENOMEM). [1]. Btw, there's in implicit limit on tb_block_nr. The vector to manage the blocks is kmalloc'ed and may not be larger than 128kb giving max 32768 blocks. Hmm... moment... seems there's a similar limit for tp_frame_nr (max 32768 frames). I'm pretty sure _that_ limit was not there when I worked with this during 2.3. Not so nice on gigabit ethernet :-( > 3. is this the general approach for the api? > [...] Looks OK too. >if (tp->status == 0) poll() for pollin on the socket /* is there a >race here? */ No race. > 4. what does the copy threshold setsockopt tuning accomplish? doesnt it always > have to copy anyway, to the mmaped area? I haven't used it myself. Reading the sources it does something different. Afaics when active if there's a packet that has been truncated by the framesize it is additionally stored in the socket's receive queue to be fetched by a normal read/recv. It notifies you about this by setting the TP_STATUS_COPY bit. So it seems to mean: copy to socket if threshold (framesize) exceeded. Ciao, ET. [1] The PACKET_RX_RING sockopt accepts all block sizes that are a multiple of PAGE_SIZE but always allocates a power of 2 size chunk. So using non power of 2 sizes will waste locked kernel memory. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: CONFIG_PACKET_MMAP help
Hi, [EMAIL PROTECTED] wrote: 1. for tp_frame_size, I dont want to truncate any data on ethernet, I need 1514 bytes, is this the best way to do it and not waste space? static const int TURBO_FRAME_SIZE= TPACKET_ALIGN(TPACKET_ALIGN(sizeof(tpacket_hdr)) + TPACKET_ALIGN(sizeof(struct sockaddr_ll)+ETH_HLEN) + 1500); Looks OK. Maybe instead of ETH_HLEN min(ETH_HLEN,16)? The framesize calculation is really strange... 2. what is tp_block_nr for? I dont understand it, I just set it to 1 and make tp_block_size big enough for all the frames I need, so its just one contiguous space, all I need is about a megabyte I think. Better go the other way around - set tb_block_size to PAGE_SIZE and tb_block_nr appropriate. tb_block_size is the contiguous physical memory the kernel tries to allocate. Anything above PAGE_SIZE is likely to fail. For you that would mean only 2 packets per 4k-page. You could try to start with bigger (power of 2) block sizes and go down to smaller ones if it fails (ENOMEM). [1]. Btw, there's in implicit limit on tb_block_nr. The vector to manage the blocks is kmalloc'ed and may not be larger than 128kb giving max 32768 blocks. Hmm... moment... seems there's a similar limit for tp_frame_nr (max 32768 frames). I'm pretty sure _that_ limit was not there when I worked with this during 2.3. Not so nice on gigabit ethernet :-( 3. is this the general approach for the api? [...] Looks OK too. if (tp-status == 0) poll() for pollin on the socket /* is there a race here? */ No race. 4. what does the copy threshold setsockopt tuning accomplish? doesnt it always have to copy anyway, to the mmaped area? I haven't used it myself. Reading the sources it does something different. Afaics when active if there's a packet that has been truncated by the framesize it is additionally stored in the socket's receive queue to be fetched by a normal read/recv. It notifies you about this by setting the TP_STATUS_COPY bit. So it seems to mean: copy to socket if threshold (framesize) exceeded. Ciao, ET. [1] The PACKET_RX_RING sockopt accepts all block sizes that are a multiple of PAGE_SIZE but always allocates a power of 2 size chunk. So using non power of 2 sizes will waste locked kernel memory. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
CONFIG_PACKET_MMAP help
Hi,
I upgrading an application to the CONFIG_PACKET_MMAP
interface, and was trying to figure out how the api works. I 'RTFS'
But had a few questions:
1. for tp_frame_size, I dont want to truncate any data on ethernet, I
need 1514 bytes, is this the best way to do it and not waste space?
static const int
TURBO_FRAME_SIZE=TPACKET_ALIGN(TPACKET_ALIGN(sizeof(tpacket_hdr))+TPACKET_ALIGN(sizeof(struct
sockaddr_ll)+ETH_HLEN) + 1500);
2. what is tp_block_nr for? I dont understand it, I just set it to 1
and make tp_block_size big enough for all the frames I need, so its
just one contiguous space, all I need is about a megabyte I think.
3. is this the general approach for the api?
open socket
set ring size
mmap()
h starts at frame[0] of the mmaped area
while(1) {
if (tp->status == 0) poll() for pollin on the socket /* is there a
race here? */
parse/copy out what I want from h + h->tp_mac
set tp->status to 0 when I am done
h = next packet in ring, or wraps
}
4. what does the copy threshold setsockopt tuning accomplish? doesnt it always
have to copy anyway, to the mmaped area?
Thanks,
c.c. me por favor...
K. Lohan
kambo at home dawt com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
CONFIG_PACKET_MMAP help
Hi,
I upgrading an application to the CONFIG_PACKET_MMAP
interface, and was trying to figure out how the api works. I 'RTFS'
But had a few questions:
1. for tp_frame_size, I dont want to truncate any data on ethernet, I
need 1514 bytes, is this the best way to do it and not waste space?
static const int
TURBO_FRAME_SIZE=TPACKET_ALIGN(TPACKET_ALIGN(sizeof(tpacket_hdr))+TPACKET_ALIGN(sizeof(struct
sockaddr_ll)+ETH_HLEN) + 1500);
2. what is tp_block_nr for? I dont understand it, I just set it to 1
and make tp_block_size big enough for all the frames I need, so its
just one contiguous space, all I need is about a megabyte I think.
3. is this the general approach for the api?
open socket
set ring size
mmap()
h starts at frame[0] of the mmaped area
while(1) {
if (tp-status == 0) poll() for pollin on the socket /* is there a
race here? */
parse/copy out what I want from h + h-tp_mac
set tp-status to 0 when I am done
h = next packet in ring, or wraps
}
4. what does the copy threshold setsockopt tuning accomplish? doesnt it always
have to copy anyway, to the mmaped area?
Thanks,
c.c. me por favor...
K. Lohan
kambo at home dawt com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
