svn commit: r366340 - head/sys/kern

[Michael Tuexen]

> On 1. Oct 2020, at 21:17, Bryan Drewery <bdrewery at FreeBSD.org> wrote:
> 
> Author: bdrewery
> Date: Thu Oct  1 19:17:03 2020
> New Revision: 366340
> URL: https://svnweb.freebsd.org/changeset/base/366340
> 
> Log:
>  Use unlocked page lookup for inmem() to avoid object lock contention
> 
>  Reviewed By:	kib, markj
>  Sponsored by:	Dell EMC Isilon
>  Submitted by:	mlaier
>  Differential Revision:	https://reviews.freebsd.org/D26597
> 
> Modified:
>  head/sys/kern/vfs_bio.c
> 
> Modified: head/sys/kern/vfs_bio.c
> ==============================================================================
> --- head/sys/kern/vfs_bio.c	Thu Oct  1 19:06:07 2020	(r366339)
> +++ head/sys/kern/vfs_bio.c	Thu Oct  1 19:17:03 2020	(r366340)
> @@ -154,7 +154,7 @@ caddr_t __read_mostly unmapped_buf;
> /* Used below and for softdep flushing threads in ufs/ffs/ffs_softdep.c */
> struct proc *bufdaemonproc;
> 
> -static int inmem(struct vnode *vp, daddr_t blkno);
> +static bool inmem(struct vnode *vp, daddr_t blkno);
> static void vm_hold_free_pages(struct buf *bp, int newbsize);
> static void vm_hold_load_pages(struct buf *bp, vm_offset_t from,
> 		vm_offset_t to);
> @@ -3586,20 +3586,21 @@ incore(struct bufobj *bo, daddr_t blkno)
>  * it also hunts around in the VM system for the data.
>  */
> 
> -static int
> +static bool
> inmem(struct vnode * vp, daddr_t blkno)
> {
> 	vm_object_t obj;
> 	vm_offset_t toff, tinc, size;
> -	vm_page_t m;
> +	vm_page_t m, n;
> 	vm_ooffset_t off;
> +	int valid;
> 
> 	ASSERT_VOP_LOCKED(vp, "inmem");
> 
> 	if (incore(&vp->v_bufobj, blkno))
> -		return 1;
> +		return (1);
> 	if (vp->v_mount == NULL)
> -		return 0;
> +		return (0);
> 	obj = vp->v_object;
> 	if (obj == NULL)
> 		return (0);
> @@ -3609,24 +3610,30 @@ inmem(struct vnode * vp, daddr_t blkno)
> 		size = vp->v_mount->mnt_stat.f_iosize;
> 	off = (vm_ooffset_t)blkno * (vm_ooffset_t)vp->v_mount->mnt_stat.f_iosize;
> 
> -	VM_OBJECT_RLOCK(obj);
> 	for (toff = 0; toff < vp->v_mount->mnt_stat.f_iosize; toff += tinc) {
> -		m = vm_page_lookup(obj, OFF_TO_IDX(off + toff));
> -		if (!m)
> -			goto notinmem;
> +		m = vm_page_lookup_unlocked(obj, OFF_TO_IDX(off + toff));
> +recheck:
> +		if (m == NULL)
> +			return (0);
> +		/*
> +		 * Consider page validity only if page mapping didn't change
> +		 * during the check.
> +		 */
> +		valid = vm_page_is_valid(m,
> +		    (vm_offset_t)((toff + off) & PAGE_MASK), tinc);
> +		n = vm_page_lookup_unlocked(obj, OFF_TO_IDX(off + toff));
Where is vm_page_lookup_unlocked() defined? For me, this breaks kernel compilation...

Best regards
Michael
> +		if (m != n) {
> +			m = n;
> +			goto recheck;
> +		}
> +		if (!valid)
> +			return (0);
> +
> 		tinc = size;
> 		if (tinc > PAGE_SIZE - ((toff + off) & PAGE_MASK))
> 			tinc = PAGE_SIZE - ((toff + off) & PAGE_MASK);
> -		if (vm_page_is_valid(m,
> -		    (vm_offset_t) ((toff + off) & PAGE_MASK), tinc) == 0)
> -			goto notinmem;
> 	}
> -	VM_OBJECT_RUNLOCK(obj);
> -	return 1;
> -
> -notinmem:
> -	VM_OBJECT_RUNLOCK(obj);
> -	return (0);
> +	return (1);
> }
> 
> /*

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