On Fri, May 30, 2008 at 05:08:10PM +0200, Michael Tuexen wrote: > Hi Vlad, > > is there any description available how the auto-tuning works? > But even with auto-tuning you still have the a_rwnd you report > to the outside world (in SACKs) and an internal value which > you use for tracking you buffer, right? > As Vlad said, there is no formal description available, but if you want a functional overview, the sk_mem_schedule api is the place to look to understand how thresholds, and memory pressure detection work Regards Neil > Best regards > Michael > > On May 30, 2008, at 3:02 PM, Vlad Yasevich wrote: > >> Neil Horman wrote: >>> On Thu, May 29, 2008 at 11:50:56AM -0400, Vlad Yasevich wrote: >>>> Neil Horman wrote: >>>>> On Thu, May 29, 2008 at 11:06:11AM -0400, Vlad Yasevich wrote: >>>> I think this is hitting a condition where the receiver buffer is >>>> exhausted prior >>>> to rwnd. We generally mark the TSN as received prior to attempting an >>>> internal allocation to carry the data. Thus, if this allocation fails, >>>> we'll continue >>>> reporting the tsn as received and move the cum-tsn if appropriate. >>>> >>>> We've been trying to figure out what the correct way to solve this >>>> condition is >>>> and so far haven't come up with a workable solution. >>>> >>> You're right it does sound like that. You know, I haven't visited that >>> code >>> since we rewrote the receive buffer management code to expand according >>> to >>> available memory with the sk_mem_schedule api. Do you think this could >>> be as >>> simple as removing this drop point? >> >> The problem is that if the user sets the buffer size, we don't auto-tune >> it. >> This is what happened in this case. However, even with auto-tunning, this >> still shows up with 1 byte data chunks. >> >> So, 2 things need to happen: >> 1) when we drop the chunk due to allocation failure, we have to remove >> the tsn from the map. This one is easy >> >> 2) We need to properly detect SWS. I haven't looked fully at this, but >> it feels a bit more involved. Implementing something like what >> BSD >> has would also work, i.e. reducing a_rwnd 1 when receive buffer is >> about to be exhausted. >> >> -vlad >> -- /**************************************************** * Neil Horman <nhorman@xxxxxxxxxxxxx> * Software Engineer, Red Hat ****************************************************/ -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
