Re: [libvirt RFC] virFile: new VIR_FILE_WRAPPER_BIG_PIPE to improve performance

diff --git a/src/util/virfile.c b/src/util/virfile.c index a04f888e06..fdacd17890 100644 --- a/src/util/virfile.c +++ b/src/util/virfile.c @@ -282,6 +282,18 @@ virFileWrapperFdNew(int *fd, const char *name, unsigned int flags) ret->cmd = virCommandNewArgList(iohelper_path, name, NULL); + if (flags & VIR_FILE_WRAPPER_BIG_PIPE) { + /* + * virsh save/resume would slow to a crawl with a default pipe size (usually 64k). + * This improves the situation by 400%, although going through io_helper still incurs + * in a performance penalty compared with a direct qemu migration to a socket. + */ + int pipe_sz, rv = virFileReadValueInt(&pipe_sz, "/proc/sys/fs/pipe-max-size"); + if (rv != 0) { + pipe_sz = 1024 * 1024; /* common default for pipe-max-size */ + } + fcntl(pipefd[output ? 0 : 1], F_SETPIPE_SZ, pipe_sz); + }