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Date: Thu, 07 Aug 2008 15:15:01 -0400
From: Vlad Yasevich <vladislav.yasevich@...com>
To: Neil Horman <nhorman@...driver.com>
Cc: linux-sctp@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] sctp: reduce memory footprint of sctp_chunk structure
Hi Neil
A few problem I found once I started testing with the new fast
retransmit regression test I just wrote.
Neil Horman wrote:
> On Fri, Jul 25, 2008 at 09:03:33AM -0400, Vlad Yasevich wrote:
>> Hi Neil
>>
>> A few small nits.
>>
> No problem, New patch attached.
>
> sctp_chunks should be put on a diet. This is some of the low hanging fruit that
> we can strip out. Changes all the __s8/__u8 flags to bitfields. Saves 12 bytes
> per chunk.
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
>
>
> include/net/sctp/structs.h | 31 +++++++++++++++++--------------
> net/sctp/output.c | 2 +-
> net/sctp/outqueue.c | 14 +++++++-------
> net/sctp/sm_make_chunk.c | 2 +-
> 4 files changed, 26 insertions(+), 23 deletions(-)
>
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index 7f25195..1f9ae90 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -731,20 +731,23 @@ struct sctp_chunk {
> */
> struct sk_buff *auth_chunk;
>
> - __u8 rtt_in_progress; /* Is this chunk used for RTT calculation? */
> - __u8 resent; /* Has this chunk ever been retransmitted. */
> - __u8 has_tsn; /* Does this chunk have a TSN yet? */
> - __u8 has_ssn; /* Does this chunk have a SSN yet? */
> - __u8 singleton; /* Was this the only chunk in the packet? */
> - __u8 end_of_packet; /* Was this the last chunk in the packet? */
> - __u8 ecn_ce_done; /* Have we processed the ECN CE bit? */
> - __u8 pdiscard; /* Discard the whole packet now? */
> - __u8 tsn_gap_acked; /* Is this chunk acked by a GAP ACK? */
> - __s8 fast_retransmit; /* Is this chunk fast retransmitted? */
> - __u8 tsn_missing_report; /* Data chunk missing counter. */
> - __u8 data_accepted; /* At least 1 chunk in this packet accepted */
> - __u8 auth; /* IN: was auth'ed | OUT: needs auth */
> - __u8 has_asconf; /* IN: have seen an asconf before */
> +#define SCTP_CAN_FRTX 0x0
> +#define SCTP_NEED_FRTX 0x1
> +#define SCTP_DONT_FRTX 0x2
> + __u16 rtt_in_progress:1, /* This chunk used for RTT calc? */
> + resent:1, /* Has this chunk ever been resent. */
> + has_tsn:1, /* Does this chunk have a TSN yet? */
> + has_ssn:1, /* Does this chunk have a SSN yet? */
> + singleton:1, /* Only chunk in the packet? */
> + end_of_packet:1, /* Last chunk in the packet? */
> + ecn_ce_done:1, /* Have we processed the ECN CE bit? */
> + pdiscard:1, /* Discard the whole packet now? */
> + tsn_gap_acked:1, /* Is this chunk acked by a GAP ACK? */
> + tsn_missing_report:1, /* Data chunk missing counter. */
tsn_missing_report needs to have at list 2 bits worth of data since it's a counter.
The good thing is that we top out at 3 missing reports, so 2 bits of data is enough.
> + data_accepted:1, /* At least 1 chunk accepted */
> + auth:1, /* IN: was auth'ed | OUT: needs auth */
> + has_asconf:1, /* IN: have seen an asconf before */
> + fast_retransmit:2; /* Is this chunk fast retransmitted? */
> };
>
> void sctp_chunk_hold(struct sctp_chunk *);
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index 7e7e612..548b567 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -709,7 +709,7 @@ static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet,
> * When a Fast Retransmit is being performed the sender SHOULD
> * ignore the value of cwnd and SHOULD NOT delay retransmission.
> */
> - if (chunk->fast_retransmit <= 0)
> + if (chunk->fast_retransmit != SCTP_CAN_FRTX)
if (chunk->fast_retransmit != SCTP_NEED_FRTX)
The origin check was to see if it was eligible for fast_rtx or already
retransmitted.
> if (transport->flight_size >= transport->cwnd) {
> retval = SCTP_XMIT_RWND_FULL;
> goto finish;
> diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
> index ace6770..34405f0 100644
> --- a/net/sctp/outqueue.c
> +++ b/net/sctp/outqueue.c
> @@ -418,7 +418,7 @@ void sctp_retransmit_mark(struct sctp_outq *q,
> * be added to the retransmit queue.
> */
> if ((reason == SCTP_RTXR_FAST_RTX &&
> - (chunk->fast_retransmit > 0)) ||
> + (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
> (reason != SCTP_RTXR_FAST_RTX && !chunk->tsn_gap_acked)) {
> /* If this chunk was sent less then 1 rto ago, do not
> * retransmit this chunk, but give the peer time
> @@ -648,8 +648,8 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
> /* Mark the chunk as ineligible for fast retransmit
> * after it is retransmitted.
> */
> - if (chunk->fast_retransmit > 0)
> - chunk->fast_retransmit = -1;
> + if (chunk->fast_retransmit == SCTP_NEED_FRTX)
> + chunk->fast_retransmit = SCTP_DONT_FRTX;
>
> /* Force start T3-rtx timer when fast retransmitting
> * the earliest outstanding TSN
> @@ -678,8 +678,8 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
> */
> if (rtx_timeout || fast_rtx) {
> list_for_each_entry(chunk1, lqueue, transmitted_list) {
> - if (chunk1->fast_retransmit > 0)
> - chunk1->fast_retransmit = -1;
> + if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
> + chunk1->fast_retransmit = SCTP_DONT_FRTX;
> }
> }
>
> @@ -1635,7 +1635,7 @@ static void sctp_mark_missing(struct sctp_outq *q,
> * chunk if it has NOT been fast retransmitted or marked for
> * fast retransmit already.
> */
> - if (!chunk->fast_retransmit &&
> + if (!(chunk->fast_retransmit == SCTP_NEED_FRTX) &&
if (chunk->fast_retransmit == SCTP_CAN_FRTX &&
That's what the test should be doing. I've already done the changes
in my tree, so this is just fyi so that your environment is fixed.
With these changes the tests pass. I'll push out the tests so you can pick
them up.
-vlad
> !chunk->tsn_gap_acked &&
> TSN_lt(tsn, highest_new_tsn_in_sack)) {
>
> @@ -1660,7 +1660,7 @@ static void sctp_mark_missing(struct sctp_outq *q,
> */
>
> if (chunk->tsn_missing_report >= 3) {
> - chunk->fast_retransmit = 1;
> + chunk->fast_retransmit = SCTP_NEED_FRTX;
> do_fast_retransmit = 1;
> }
> }
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 3b55ad1..c9264dc 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -1195,7 +1195,7 @@ struct sctp_chunk *sctp_chunkify(struct sk_buff *skb,
> */
> retval->tsn_missing_report = 0;
> retval->tsn_gap_acked = 0;
> - retval->fast_retransmit = 0;
> + retval->fast_retransmit = SCTP_CAN_FRTX;
>
> /* If this is a fragmented message, track all fragments
> * of the message (for SEND_FAILED).
>
--
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