Date: Thu, 13 Oct 2011 14:34:57 GMT From: John Baldwin <jhb@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 200151 for review Message-ID: <201110131434.p9DEYvop078187@skunkworks.freebsd.org>
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http://p4web.freebsd.org/@@200151?ac=10 Change 200151 by jhb@jhb_jhbbsd on 2011/10/13 14:34:24 First cut at implement fadvise() for read. This works by adjusting the behavior in IO flag. I should do at least some of this in the write case as well. Affected files ... .. //depot/projects/fadvise/sys/kern/vfs_vnops.c#2 edit Differences ... ==== //depot/projects/fadvise/sys/kern/vfs_vnops.c#2 (text+ko) ==== @@ -518,7 +518,7 @@ struct vnode *vp; int error, ioflag; struct mtx *mtxp; - int vfslocked; + int advice, vfslocked; KASSERT(uio->uio_td == td, ("uio_td %p is not td %p", uio->uio_td, td)); @@ -529,27 +529,48 @@ ioflag |= IO_NDELAY; if (fp->f_flag & O_DIRECT) ioflag |= IO_DIRECT; + advice = FADV_NORMAL; vfslocked = VFS_LOCK_GIANT(vp->v_mount); /* * According to McKusick the vn lock was protecting f_offset here. * It is now protected by the FOFFSET_LOCKED flag. */ - if ((flags & FOF_OFFSET) == 0) { + if ((flags & FOF_OFFSET) == 0 || fp->f_advice != FADV_NORMAL) { mtxp = mtx_pool_find(mtxpool_sleep, fp); mtx_lock(mtxp); - while(fp->f_vnread_flags & FOFFSET_LOCKED) { - fp->f_vnread_flags |= FOFFSET_LOCK_WAITING; - msleep(&fp->f_vnread_flags, mtxp, PUSER -1, - "vnread offlock", 0); + if ((flags & FOF_OFFSET) == 0) { + while (fp->f_vnread_flags & FOFFSET_LOCKED) { + fp->f_vnread_flags |= FOFFSET_LOCK_WAITING; + msleep(&fp->f_vnread_flags, mtxp, PUSER -1, + "vnread offlock", 0); + } + fp->f_vnread_flags |= FOFFSET_LOCKED; + uio->uio_offset = fp->f_offset; } - fp->f_vnread_flags |= FOFFSET_LOCKED; + if (fp->f_advice != FADV_NORMAL && + uio->uio_offset >= fp->f_advstart && + uio->uio_offset + uio->uio_resid <= fp->f_advend) + advice = fp->f_advice; mtx_unlock(mtxp); - vn_lock(vp, LK_SHARED | LK_RETRY); - uio->uio_offset = fp->f_offset; - } else - vn_lock(vp, LK_SHARED | LK_RETRY); + } + vn_lock(vp, LK_SHARED | LK_RETRY); - ioflag |= sequential_heuristic(uio, fp); + switch (advice) { + case FADV_NORMAL: + case FADV_SEQUENTIAL: + ioflag |= sequential_heuristic(uio, fp); + break; + case FADV_RANDOM: + /* Do no read-ahead for random I/O. */ + break; + case FADV_NOREUSE: + /* + * Request the underlying FS to discard the pages + * after the I/O is complete. + */ + ioflag |= IO_DIRECT; + break; + } #ifdef MAC error = mac_vnode_check_read(active_cred, fp->f_cred, vp);
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