On 5/6/08 4:18 PM, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > On Mon, May 05, 2008 at 09:26:02PM -0500, Tom Tucker wrote: >> >> >> >> On 5/5/08 5:06 PM, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: >> >>> On Fri, May 02, 2008 at 11:28:34AM -0500, Tom Tucker wrote: >>>> The svc_rdma_send function will attempt to reap SQ WR to make room for >>>> a new request if it finds the SQ full. This function races with the >>>> dto_tasklet that also reaps SQ WR. To avoid calling the function >>>> unnecessarily use test_and_clear_bit with the RDMAXPRT_SQ_PENDING >>>> flag to serialize access to the sq_cq_reap function. >>> >>> OK. I won't pretend to understand much of this, but--would it be worth >>> pulling out the added code here into a helper function, since it now >>> exists in two different places? (Especially if correctness depends on >>> the same thing happening in both the places this bit can be cleared.) >> >> Yes. Good suggestions. >> >> BTW, this code is here because the SQ is undersized for big data. Since a >> single NFS_READ/WRITE can result in an attempt to fetch a large amount of >> data from the client (2M) and depending on certain HW resources this can >> result in a lot of WR being posted to the SQ. > > WR is write request, SQ is send queue? (In which case this happens on > nfs read operations?) I'm behind.... > >> That said, there is a change coming in the 2.6.27 time frame that supports >> what is called Fast NSMR register. This allows the transport to effectively >> DMA map the entire transfer size (32k -- 2M) all as a single SGE. This will >> take a lot of pressure off the SQ and effectively make this code >> unnecessary. > > OK! > > Ideally we'd have patches for 2.6.27 in linux-next for a little while > first, so we should try to have that ready in a month or so, when the > -rc's start looking final. It may be .28 then. A lot of pieces have to come together... > > --b. > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
