On 4/19/25 1:28 PM, cel@xxxxxxxxxx wrote: > From: Chuck Lever <chuck.lever@xxxxxxxxxx> > > In order to make RPCSVC_MAXPAYLOAD larger (or variable in size), we > need to do something clever with the payload arrays embedded in > struct svc_rqst and elsewhere. > > My preference is to keep these arrays allocated all the time because > allocating them on demand increases the risk of a memory allocation > failure during a large I/O. This is a quick-and-dirty approach that > might be replaced once NFSD is converted to use large folios. > > The downside of this design choice is that it pins a few pages per > NFSD thread (and that's the current situation already). But note > that because RPCSVC_MAXPAGES is 259, each array is just over a page > in size, making the allocation waste quite a bit of memory beyond > the end of the array due to power-of-2 allocator round up. This gets > worse as the MAXPAGES value is doubled or quadrupled. > > This series also addresses similar issues in the socket and RDMA > transports. I forgot to note that this series has other benefits besides making these arrays flexible in size. The reduction in size of struct svc_rqst to under half a page is kind of a big deal. > Chuck Lever (9): > sunrpc: Remove backchannel check in svc_init_buffer() > sunrpc: Add a helper to derive maxpages from sv_max_mesg > sunrpc: Replace the rq_pages array with dynamically-allocated memory > sunrpc: Replace the rq_vec array with dynamically-allocated memory > sunrpc: Replace the rq_bvec array with dynamically-allocated memory > sunrpc: Adjust size of socket's receive page array dynamically > svcrdma: Adjust the number of RDMA contexts per transport > svcrdma: Adjust the number of entries in svc_rdma_recv_ctxt::rc_pages > svcrdma: Adjust the number of entries in svc_rdma_send_ctxt::sc_pages > > fs/nfsd/nfs4proc.c | 1 - > fs/nfsd/vfs.c | 2 +- > include/linux/sunrpc/svc.h | 19 +++++++-- > include/linux/sunrpc/svc_rdma.h | 6 ++- > include/linux/sunrpc/svcsock.h | 4 +- > net/sunrpc/svc.c | 51 +++++++++++++++--------- > net/sunrpc/svc_xprt.c | 10 +---- > net/sunrpc/svcsock.c | 15 ++++--- > net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 8 +++- > net/sunrpc/xprtrdma/svc_rdma_rw.c | 2 +- > net/sunrpc/xprtrdma/svc_rdma_sendto.c | 16 ++++++-- > net/sunrpc/xprtrdma/svc_rdma_transport.c | 2 +- > 12 files changed, 88 insertions(+), 48 deletions(-) > -- Chuck Lever
