On 5/6/22 1:00 AM, Hao Xu wrote: > Let multishot support multishot mode, currently only add accept as its > first comsumer. > theoretical analysis: > 1) when connections come in fast > - singleshot: > add accept sqe(userpsace) --> accept inline > ^ | > |-----------------| > - multishot: > add accept sqe(userspace) --> accept inline > ^ | > |--*--| > > we do accept repeatedly in * place until get EAGAIN > > 2) when connections come in at a low pressure > similar thing like 1), we reduce a lot of userspace-kernel context > switch and useless vfs_poll() > > > tests: > Did some tests, which goes in this way: > > server client(multiple) > accept connect > read write > write read > close close > > Basically, raise up a number of clients(on same machine with server) to > connect to the server, and then write some data to it, the server will > write those data back to the client after it receives them, and then > close the connection after write return. Then the client will read the > data and then close the connection. Here I test 10000 clients connect > one server, data size 128 bytes. And each client has a go routine for > it, so they come to the server in short time. > test 20 times before/after this patchset, time spent:(unit cycle, which > is the return value of clock()) > before: > 1930136+1940725+1907981+1947601+1923812+1928226+1911087+1905897+1941075 > +1934374+1906614+1912504+1949110+1908790+1909951+1941672+1969525+1934984 > +1934226+1914385)/20.0 = 1927633.75 > after: > 1858905+1917104+1895455+1963963+1892706+1889208+1874175+1904753+1874112 > +1874985+1882706+1884642+1864694+1906508+1916150+1924250+1869060+1889506 > +1871324+1940803)/20.0 = 1894750.45 > > (1927633.75 - 1894750.45) / 1927633.75 = 1.65% > > > A liburing test is here: > https://github.com/HowHsu/liburing/blob/multishot_accept/test/accept.c Wish I had seen that, I wrote my own! But maybe that's good, you tend to find other issues through that. Anyway, works for me in testing, and I can see this being a nice win for accept intensive workloads. I pushed a bunch of cleanup patches that should just get folded in. Can you fold them into your patches and address the other feedback, and post a v3? I pushed the test branch here: https://git.kernel.dk/cgit/linux-block/log/?h=fastpoll-mshot -- Jens Axboe
