diff options
Diffstat (limited to 'ext/kgio/writev.c')
| -rw-r--r-- | ext/kgio/writev.c | 317 |
1 files changed, 317 insertions, 0 deletions
diff --git a/ext/kgio/writev.c b/ext/kgio/writev.c new file mode 100644 index 0000000..a723b68 --- /dev/null +++ b/ext/kgio/writev.c @@ -0,0 +1,317 @@ +/* + * we're currently too lazy to use rb_ensure to free an allocation, so we + * the abuse rb_str_* API for a temporary buffer + */ +#define RSTRING_MODIFIED 1 + +#include "kgio.h" +#include "my_fileno.h" +#include "nonblock.h" +#ifdef HAVE_WRITEV +# include <sys/uio.h> +# define USE_WRITEV 1 +#else +# define USE_WRITEV 0 +static ssize_t assert_writev(int fd, void* iov, int len) +{ + assert(0 && "you should not try to call writev"); + return -1; +} +# define writev assert_writev +#endif +static VALUE sym_wait_writable; + +#ifndef HAVE_WRITEV +#define iovec my_iovec +struct my_iovec { + void *iov_base; + size_t iov_len; +}; +#endif + +/* tests for choosing following constants were done on Linux 3.0 x86_64 + * (Ubuntu 12.04) Core i3 i3-2330M slowed to 1600MHz + * testing script https://gist.github.com/2850641 + * fill free to make more thorough testing and choose better value + */ + +/* test shows that its meaningless to set WRITEV_MEMLIMIT more that 1M + * even when tcp_wmem set to relatively high value (2M) (in fact, it becomes + * even slower). 512K performs a bit better in average case. */ +#define WRITEV_MEMLIMIT (512*1024) +/* same test shows that custom_writev is faster than glibc writev when + * average string is smaller than ~500 bytes and slower when average strings + * is greater then ~600 bytes. 512 bytes were choosen cause current compilers + * turns x/512 into x>>9 */ +#define WRITEV_IMPL_THRESHOLD 512 + +static unsigned int iov_max = 1024; /* this could be overriden in init */ + +struct wrv_args { + VALUE io; + VALUE buf; + VALUE vec_buf; /* FIXME: this requires RSTRING_MODIFY for rbx */ + struct iovec *vec; + unsigned long iov_cnt; + size_t batch_len; + int something_written; + int fd; +}; + +static ssize_t custom_writev(int fd, const struct iovec *vec, unsigned int iov_cnt, size_t total_len) +{ + unsigned int i; + ssize_t result; + char *buf, *curbuf; + const struct iovec *curvec = vec; + + /* we do not want to use ruby's xmalloc because + * it can fire GC, and we'll free buffer shortly anyway */ + curbuf = buf = malloc(total_len); + if (buf == NULL) return -1; + + for (i = 0; i < iov_cnt; i++, curvec++) { + memcpy(curbuf, curvec->iov_base, curvec->iov_len); + curbuf += curvec->iov_len; + } + + result = write(fd, buf, total_len); + + /* well, it seems that `free` could not change errno + * but lets save it anyway */ + i = errno; + free(buf); + errno = i; + + return result; +} + +static void prepare_writev(struct wrv_args *a, VALUE io, VALUE ary) +{ + a->io = io; + a->fd = my_fileno(io); + a->something_written = 0; + + if (TYPE(ary) == T_ARRAY) + /* rb_ary_subseq will not copy array unless it modified */ + a->buf = rb_ary_subseq(ary, 0, RARRAY_LEN(ary)); + else + a->buf = rb_Array(ary); + + a->vec_buf = rb_str_new(0, 0); + a->vec = NULL; +} + +static void fill_iovec(struct wrv_args *a) +{ + unsigned long i; + struct iovec *curvec; + + a->iov_cnt = RARRAY_LEN(a->buf); + a->batch_len = 0; + if (a->iov_cnt == 0) return; + if (a->iov_cnt > iov_max) a->iov_cnt = iov_max; + rb_str_resize(a->vec_buf, sizeof(struct iovec) * a->iov_cnt); + curvec = a->vec = (struct iovec*)RSTRING_PTR(a->vec_buf); + + for (i=0; i < a->iov_cnt; i++, curvec++) { + VALUE str = rb_ary_entry(a->buf, i); + long str_len, next_len; + + if (TYPE(str) != T_STRING) { + str = rb_obj_as_string(str); + rb_ary_store(a->buf, i, str); + } + + str_len = RSTRING_LEN(str); + + /* lets limit total memory to write, + * but always take first string */ + next_len = a->batch_len + str_len; + if (i && next_len > WRITEV_MEMLIMIT) { + a->iov_cnt = i; + break; + } + a->batch_len = next_len; + + curvec->iov_base = RSTRING_PTR(str); + curvec->iov_len = str_len; + } +} + +static long trim_writev_buffer(struct wrv_args *a, long n) +{ + long i; + long ary_len = RARRAY_LEN(a->buf); + + if (n == (long)a->batch_len) { + i = a->iov_cnt; + n = 0; + } else { + for (i = 0; n && i < ary_len; i++) { + VALUE entry = rb_ary_entry(a->buf, i); + n -= RSTRING_LEN(entry); + if (n < 0) break; + } + } + + /* all done */ + if (i == ary_len) { + assert(n == 0 && "writev system call is broken"); + a->buf = Qnil; + return 0; + } + + /* partially done, remove fully-written buffers */ + if (i > 0) + a->buf = rb_ary_subseq(a->buf, i, ary_len - i); + + /* setup+replace partially written buffer */ + if (n < 0) { + VALUE str = rb_ary_entry(a->buf, 0); + long str_len = RSTRING_LEN(str); + str = rb_str_subseq(str, str_len + n, -n); + rb_ary_store(a->buf, 0, str); + } + return RARRAY_LEN(a->buf); +} + +static int writev_check(struct wrv_args *a, long n, const char *msg, int io_wait) +{ + if (n >= 0) { + if (n > 0) a->something_written = 1; + return trim_writev_buffer(a, n); + } else if (n < 0) { + if (errno == EINTR) { + a->fd = my_fileno(a->io); + return -1; + } + if (errno == EAGAIN) { + if (io_wait) { + (void)kgio_call_wait_writable(a->io); + return -1; + } else if (!a->something_written) { + a->buf = sym_wait_writable; + } + return 0; + } + kgio_wr_sys_fail(msg); + } + return 0; +} + +static VALUE my_writev(VALUE io, VALUE ary, int io_wait) +{ + struct wrv_args a; + long n; + + prepare_writev(&a, io, ary); + set_nonblocking(a.fd); + + do { + fill_iovec(&a); + if (a.iov_cnt == 0) + n = 0; + else if (a.iov_cnt == 1) + n = (long)write(a.fd, a.vec[0].iov_base, + a.vec[0].iov_len); + /* for big strings use library function */ + else if (USE_WRITEV && + ((a.batch_len / WRITEV_IMPL_THRESHOLD) > a.iov_cnt)) + n = (long)writev(a.fd, a.vec, a.iov_cnt); + else + n = (long)custom_writev(a.fd, a.vec, a.iov_cnt, + a.batch_len); + } while (writev_check(&a, n, "writev", io_wait) != 0); + rb_str_resize(a.vec_buf, 0); + + if (TYPE(a.buf) != T_SYMBOL) + kgio_autopush_write(io); + return a.buf; +} + +/* + * call-seq: + * + * io.kgio_writev(array) -> nil + * + * Returns nil when the write completes. + * + * This may block and call any method defined to +kgio_wait_writable+ + * for the class. + * + * Note: it uses +Array()+ semantic for converting argument, so that + * it will succeed if you pass something else. + */ +static VALUE kgio_writev(VALUE io, VALUE ary) +{ + return my_writev(io, ary, 1); +} + +/* + * call-seq: + * + * io.kgio_trywritev(array) -> nil, Array or :wait_writable + * + * Returns nil if the write was completed in full. + * + * Returns an Array of strings containing the unwritten portion + * if EAGAIN was encountered, but some portion was successfully written. + * + * Returns :wait_writable if EAGAIN is encountered and nothing + * was written. + * + * Note: it uses +Array()+ semantic for converting argument, so that + * it will succeed if you pass something else. + */ +static VALUE kgio_trywritev(VALUE io, VALUE ary) +{ + return my_writev(io, ary, 0); +} + +/* + * call-seq: + * + * Kgio.trywritev(io, array) -> nil, Array or :wait_writable + * + * Returns nil if the write was completed in full. + * + * Returns a Array of strings containing the unwritten portion if EAGAIN + * was encountered, but some portion was successfully written. + * + * Returns :wait_writable if EAGAIN is encountered and nothing + * was written. + * + * Maybe used in place of PipeMethods#kgio_trywritev for non-Kgio objects + */ +static VALUE s_trywritev(VALUE mod, VALUE io, VALUE ary) +{ + return kgio_trywritev(io, ary); +} + +void init_kgio_writev(void) +{ +#ifdef IOV_MAX + unsigned int sys_iov_max = IOV_MAX; +#else + unsigned int sys_iov_max = sysconf(_SC_IOV_MAX); +#endif + + VALUE mPipeMethods, mSocketMethods; + VALUE mKgio = rb_define_module("Kgio"); + + if (sys_iov_max < iov_max) + iov_max = sys_iov_max; + + sym_wait_writable = ID2SYM(rb_intern("wait_writable")); + + rb_define_singleton_method(mKgio, "trywritev", s_trywritev, 2); + + mPipeMethods = rb_define_module_under(mKgio, "PipeMethods"); + rb_define_method(mPipeMethods, "kgio_writev", kgio_writev, 1); + rb_define_method(mPipeMethods, "kgio_trywritev", kgio_trywritev, 1); + + mSocketMethods = rb_define_module_under(mKgio, "SocketMethods"); + rb_define_method(mSocketMethods, "kgio_writev", kgio_writev, 1); + rb_define_method(mSocketMethods, "kgio_trywritev", kgio_trywritev, 1); +} |