Date: Fri, 7 Aug 2015 04:38:14 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r286399 - stable/10/sys/kern Message-ID: <201508070438.t774cEqs015134@repo.freebsd.org>
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Author: kib Date: Fri Aug 7 04:38:13 2015 New Revision: 286399 URL: https://svnweb.freebsd.org/changeset/base/286399 Log: MFC r286106: Provide a prefaulting for the userspace i/o buffers, disabled by default. Modified: stable/10/sys/kern/vfs_vnops.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/kern/vfs_vnops.c ============================================================================== --- stable/10/sys/kern/vfs_vnops.c Fri Aug 7 04:35:43 2015 (r286398) +++ stable/10/sys/kern/vfs_vnops.c Fri Aug 7 04:38:13 2015 (r286399) @@ -110,6 +110,9 @@ static const int io_hold_cnt = 16; static int vn_io_fault_enable = 1; SYSCTL_INT(_debug, OID_AUTO, vn_io_fault_enable, CTLFLAG_RW, &vn_io_fault_enable, 0, "Enable vn_io_fault lock avoidance"); +static int vn_io_fault_prefault = 0; +SYSCTL_INT(_debug, OID_AUTO, vn_io_fault_prefault, CTLFLAG_RW, + &vn_io_fault_prefault, 0, "Enable vn_io_fault prefaulting"); static u_long vn_io_faults_cnt; SYSCTL_ULONG(_debug, OID_AUTO, vn_io_faults, CTLFLAG_RD, &vn_io_faults_cnt, 0, "Count of vn_io_fault lock avoidance triggers"); @@ -1008,6 +1011,59 @@ vn_io_fault_doio(struct vn_io_fault_args uio->uio_rw); } +static int +vn_io_fault_touch(char *base, const struct uio *uio) +{ + int r; + + r = fubyte(base); + if (r == -1 || (uio->uio_rw == UIO_READ && subyte(base, r) == -1)) + return (EFAULT); + return (0); +} + +static int +vn_io_fault_prefault_user(const struct uio *uio) +{ + char *base; + const struct iovec *iov; + size_t len; + ssize_t resid; + int error, i; + + KASSERT(uio->uio_segflg == UIO_USERSPACE, + ("vn_io_fault_prefault userspace")); + + error = i = 0; + iov = uio->uio_iov; + resid = uio->uio_resid; + base = iov->iov_base; + len = iov->iov_len; + while (resid > 0) { + error = vn_io_fault_touch(base, uio); + if (error != 0) + break; + if (len < PAGE_SIZE) { + if (len != 0) { + error = vn_io_fault_touch(base + len - 1, uio); + if (error != 0) + break; + resid -= len; + } + if (++i >= uio->uio_iovcnt) + break; + iov = uio->uio_iov + i; + base = iov->iov_base; + len = iov->iov_len; + } else { + len -= PAGE_SIZE; + base += PAGE_SIZE; + resid -= PAGE_SIZE; + } + } + return (error); +} + /* * Common code for vn_io_fault(), agnostic to the kind of i/o request. * Uses vn_io_fault_doio() to make the call to an actual i/o function. @@ -1029,6 +1085,12 @@ vn_io_fault1(struct vnode *vp, struct ui ssize_t adv; int error, cnt, save, saveheld, prev_td_ma_cnt; + if (vn_io_fault_prefault) { + error = vn_io_fault_prefault_user(uio); + if (error != 0) + return (error); /* Or ignore ? */ + } + prot = uio->uio_rw == UIO_READ ? VM_PROT_WRITE : VM_PROT_READ; /*
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