what is fsck's "slowdown"?

Marc G. Fournier scrappy at hub.org
Fri Sep 24 12:07:35 PDT 2004


Just curious as to whether or not this is going to get applied to the 
source tree ... ?  Just checked my -current, and it isn't there yet, just 
wanted to see if maybe its been forgotten? :(




On Sun, 5 Sep 2004, Don Lewis wrote:

> On  4 Sep, To: scrappy at hub.org wrote:
>> On  4 Sep, Don Lewis wrote:
>>> On  4 Sep, Marc G. Fournier wrote:
>>>> On Fri, 3 Sep 2004, Don Lewis wrote:
>>>
>>>>> Would the file system in question happen to be full of UNREF files that
>>>>> fsck is deleting?
>>>>
>>>> mostly 'ZERO LENGTH DIRECTORY' ...
>>>
>>> I'm pretty sure that I understand the problem now.  During pass 4, fsck
>>> looks at each inode.  It checks each inode in the FSTATE and DFOUND
>>> states to see if their link counts need to be adjusted.  If the link
>>> count does not need to be adjusted, fsck checks to see if the inode is
>>> on the list of inodes whose initial link counts were zero, and if it
>>> finds the inode on this list, it clears the inode.
>>>
>>> The problem is that the zero length directories get added to this list
>>> if their initial link count is zero, and they also don't get removed
>>> from the list because they are in the DCLEAR state, so the list doesn't
>>> shrink.  This bloats the list, which greatly slows down processing of
>>> normal files and directories.
>>>
>>> Deleting unreferenced files is not the biggest bottleneck, so reversing
>>> the order of the list isn't going to help much.  Probably the biggest
>>> speedup could be gained by keeping the zero length directories off the
>>> list.
>>
>> An even better solution would be to dispense with the zln list entirely
>> and just set a bit for these inodes in their struct inostat.  This
>> change is a bit more intrusive because of the need for some sort of
>> packing strategy because of the need to keep this structure small.  My
>> initial inclination would be to add two new states, FZERO and DZERO,
>> that pass1() would use to mark inodes with a zero link count.
>
> Here's a patch that eliminates the zln list and adds two new inode
> states to tag zero files and directories that have a zero link count. It
> seems to work in the light testing that I have done, but it needs
> further and review before it gets committed.
>
> Index: sbin/fsck_ffs/dir.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/dir.c,v
> retrieving revision 1.29
> diff -u -r1.29 dir.c
> --- sbin/fsck_ffs/dir.c	1 Sep 2004 05:48:06 -0000	1.29
> +++ sbin/fsck_ffs/dir.c	5 Sep 2004 21:20:56 -0000
> @@ -90,7 +90,8 @@
> 			if (inp->i_parent == 0)
> 				continue;
> 			if (inoinfo(inp->i_parent)->ino_state == DFOUND &&
> -			    inoinfo(inp->i_number)->ino_state == DSTATE) {
> +			    (inoinfo(inp->i_number)->ino_state == DSTATE ||
> +			    inoinfo(inp->i_number)->ino_state == DZLINK)) {
> 				inoinfo(inp->i_number)->ino_state = DFOUND;
> 				change++;
> 			}
> @@ -640,7 +641,8 @@
> 		return(ino);
> 	}
> 	if (inoinfo(parent)->ino_state != DSTATE &&
> -	    inoinfo(parent)->ino_state != DFOUND) {
> +	    inoinfo(parent)->ino_state != DFOUND &&
> +	    inoinfo(parent)->ino_state != DZLINK) {
> 		freeino(ino);
> 		return (0);
> 	}
> Index: sbin/fsck_ffs/fsck.h
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/fsck.h,v
> retrieving revision 1.32
> diff -u -r1.32 fsck.h
> --- sbin/fsck_ffs/fsck.h	1 Sep 2004 05:48:06 -0000	1.32
> +++ sbin/fsck_ffs/fsck.h	6 Sep 2004 00:41:31 -0000
> @@ -84,6 +84,8 @@
> #define	DFOUND	04		/* directory found during descent */
> #define	DCLEAR	05		/* directory is to be cleared */
> #define	FCLEAR	06		/* file is to be cleared */
> +#define	FZLINK	07		/* inode is file with a link count of zero */
> +#define	DZLINK	10		/* inode is directory with a zero link count  */
> /*
>  * Inode state information is contained on per cylinder group lists
>  * which are described by the following structure.
> @@ -205,15 +207,6 @@
> struct dups *muldup;		/* end of unique duplicate dup block numbers */
>
> /*
> - * Linked list of inodes with zero link counts.
> - */
> -struct zlncnt {
> -	struct zlncnt *next;
> -	ino_t zlncnt;
> -};
> -struct zlncnt *zlnhead;		/* head of zero link count list */
> -
> -/*
>  * Inode cache data structures.
>  */
> struct inoinfo {
> Index: sbin/fsck_ffs/fsutil.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/fsutil.c,v
> retrieving revision 1.24
> diff -u -r1.24 fsutil.c
> --- sbin/fsck_ffs/fsutil.c	18 May 2004 19:51:41 -0000	1.24
> +++ sbin/fsck_ffs/fsutil.c	5 Sep 2004 21:24:41 -0000
> @@ -525,7 +525,8 @@
> 	}
> 	if (busy ||
> 	    (inoinfo(curdir)->ino_state != DSTATE &&
> -	     inoinfo(curdir)->ino_state != DFOUND)) {
> +	     inoinfo(curdir)->ino_state != DFOUND &&
> +	     inoinfo(curdir)->ino_state != DZLINK)) {
> 		(void)strcpy(namebuf, "?");
> 		return;
> 	}
> Index: sbin/fsck_ffs/inode.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/inode.c,v
> retrieving revision 1.36
> diff -u -r1.36 inode.c
> --- sbin/fsck_ffs/inode.c	1 Sep 2004 05:48:06 -0000	1.36
> +++ sbin/fsck_ffs/inode.c	5 Sep 2004 21:25:36 -0000
> @@ -576,10 +576,12 @@
> 	switch (inoinfo(ino)->ino_state) {
>
> 	case FSTATE:
> +	case FZLINK:
> 		inoinfo(ino)->ino_state = FCLEAR;
> 		return;
>
> 	case DSTATE:
> +	case DZLINK:
> 		inoinfo(ino)->ino_state = DCLEAR;
> 		return;
>
> Index: sbin/fsck_ffs/main.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/main.c,v
> retrieving revision 1.41
> diff -u -r1.41 main.c
> --- sbin/fsck_ffs/main.c	9 Apr 2004 19:58:28 -0000	1.41
> +++ sbin/fsck_ffs/main.c	6 Sep 2004 00:41:47 -0000
> @@ -194,7 +194,6 @@
> 	struct ufs_args args;
> 	struct dups *dp;
> 	struct statfs *mntp;
> -	struct zlncnt *zlnp;
> 	struct stat snapdir;
> 	struct group *grp;
> 	ufs2_daddr_t blks;
> @@ -424,14 +423,7 @@
> 				printf(" %lld,", (long long)dp->dup);
> 			printf("\n");
> 		}
> -		if (zlnhead != NULL) {
> -			printf("The following zero link count inodes remain:");
> -			for (zlnp = zlnhead; zlnp; zlnp = zlnp->next)
> -				printf(" %u,", zlnp->zlncnt);
> -			printf("\n");
> -		}
> 	}
> -	zlnhead = (struct zlncnt *)0;
> 	duplist = (struct dups *)0;
> 	muldup = (struct dups *)0;
> 	inocleanup();
> Index: sbin/fsck_ffs/pass1.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/pass1.c,v
> retrieving revision 1.42
> diff -u -r1.42 pass1.c
> --- sbin/fsck_ffs/pass1.c	1 Sep 2004 05:48:06 -0000	1.42
> +++ sbin/fsck_ffs/pass1.c	6 Sep 2004 00:42:11 -0000
> @@ -189,7 +189,6 @@
> checkinode(ino_t inumber, struct inodesc *idesc)
> {
> 	union dinode *dp;
> -	struct zlncnt *zlnp;
> 	off_t kernmaxfilesize;
> 	ufs2_daddr_t ndb;
> 	mode_t mode;
> @@ -302,28 +301,18 @@
> 		goto unknown;
> 	n_files++;
> 	inoinfo(inumber)->ino_linkcnt = DIP(dp, di_nlink);
> -	if (DIP(dp, di_nlink) <= 0) {
> -		zlnp = (struct zlncnt *)malloc(sizeof *zlnp);
> -		if (zlnp == NULL) {
> -			pfatal("LINK COUNT TABLE OVERFLOW");
> -			if (reply("CONTINUE") == 0) {
> -				ckfini(0);
> -				exit(EEXIT);
> -			}
> -		} else {
> -			zlnp->zlncnt = inumber;
> -			zlnp->next = zlnhead;
> -			zlnhead = zlnp;
> -		}
> -	}
> 	if (mode == IFDIR) {
> 		if (DIP(dp, di_size) == 0)
> 			inoinfo(inumber)->ino_state = DCLEAR;
> +		else if (DIP(dp, di_nlink) <= 0)
> +			inoinfo(inumber)->ino_state = DZLINK;
> 		else
> 			inoinfo(inumber)->ino_state = DSTATE;
> 		cacheino(dp, inumber);
> 		countdirs++;
> -	} else
> +	} else if (DIP(dp, di_nlink) <= 0)
> +		inoinfo(inumber)->ino_state = FZLINK;
> +	else
> 		inoinfo(inumber)->ino_state = FSTATE;
> 	inoinfo(inumber)->ino_type = IFTODT(mode);
> 	badblk = dupblk = 0;
> Index: sbin/fsck_ffs/pass2.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/pass2.c,v
> retrieving revision 1.25
> diff -u -r1.25 pass2.c
> --- sbin/fsck_ffs/pass2.c	1 Sep 2004 05:48:06 -0000	1.25
> +++ sbin/fsck_ffs/pass2.c	5 Sep 2004 21:36:06 -0000
> @@ -91,6 +91,7 @@
>
> 	case FSTATE:
> 	case FCLEAR:
> +	case FZLINK:
> 		pfatal("ROOT INODE NOT DIRECTORY");
> 		if (reply("REALLOCATE")) {
> 			freeino(ROOTINO);
> @@ -109,6 +110,7 @@
> 		break;
>
> 	case DSTATE:
> +	case DZLINK:
> 		break;
>
> 	default:
> @@ -196,7 +198,8 @@
> 		if (inp->i_parent == 0 || inp->i_isize == 0)
> 			continue;
> 		if (inoinfo(inp->i_parent)->ino_state == DFOUND &&
> -		    inoinfo(inp->i_number)->ino_state == DSTATE)
> +		    (inoinfo(inp->i_number)->ino_state == DSTATE ||
> +		    inoinfo(inp->i_number)->ino_state == DZLINK))
> 			inoinfo(inp->i_number)->ino_state = DFOUND;
> 		if (inp->i_dotdot == inp->i_parent ||
> 		    inp->i_dotdot == (ino_t)-1)
> @@ -405,6 +408,7 @@
> 			goto again;
>
> 		case DSTATE:
> +		case DZLINK:
> 			if (inoinfo(idesc->id_number)->ino_state == DFOUND)
> 				inoinfo(dirp->d_ino)->ino_state = DFOUND;
> 			/* FALLTHROUGH */
> @@ -435,6 +439,7 @@
> 			/* FALLTHROUGH */
>
> 		case FSTATE:
> +		case FZLINK:
> 			if (dirp->d_type != inoinfo(dirp->d_ino)->ino_type) {
> 				fileerror(idesc->id_number, dirp->d_ino,
> 				    "BAD TYPE VALUE");
> Index: sbin/fsck_ffs/pass3.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/pass3.c,v
> retrieving revision 1.14
> diff -u -r1.14 pass3.c
> --- sbin/fsck_ffs/pass3.c	9 Apr 2004 19:58:28 -0000	1.14
> +++ sbin/fsck_ffs/pass3.c	6 Sep 2004 00:25:50 -0000
> @@ -69,7 +69,7 @@
> 		inp = inpsort[inpindex];
> 		state = inoinfo(inp->i_number)->ino_state;
> 		if (inp->i_number == ROOTINO ||
> -		    (inp->i_parent != 0 && state != DSTATE))
> +		    (inp->i_parent != 0 && state != DSTATE && state != DZLINK))
> 			continue;
> 		if (state == DCLEAR)
> 			continue;
> @@ -80,7 +80,8 @@
> 		 * in pass 4.
> 		 */
> 		if ((preen || bkgrdflag) &&
> -		    resolved && usedsoftdep && state == DSTATE) {
> +		    resolved && usedsoftdep && (state == DSTATE ||
> +	            state == DZLINK)) {
> 			if (inp->i_dotdot >= ROOTINO)
> 				inoinfo(inp->i_dotdot)->ino_linkcnt++;
> 			continue;
> @@ -88,7 +89,8 @@
> 		for (loopcnt = 0; ; loopcnt++) {
> 			orphan = inp->i_number;
> 			if (inp->i_parent == 0 ||
> -			    inoinfo(inp->i_parent)->ino_state != DSTATE ||
> +			    (inoinfo(inp->i_parent)->ino_state != DSTATE &&
> +			    inoinfo(inp->i_parent)->ino_state != DZLINK) ||
> 			    loopcnt > countdirs)
> 				break;
> 			inp = getinoinfo(inp->i_parent);
> Index: sbin/fsck_ffs/pass4.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/pass4.c,v
> retrieving revision 1.14
> diff -u -r1.14 pass4.c
> --- sbin/fsck_ffs/pass4.c	9 Apr 2004 19:58:28 -0000	1.14
> +++ sbin/fsck_ffs/pass4.c	6 Sep 2004 00:41:55 -0000
> @@ -49,7 +49,6 @@
> pass4(void)
> {
> 	ino_t inumber;
> -	struct zlncnt *zlnp;
> 	union dinode *dp;
> 	struct inodesc idesc;
> 	int i, n, cg;
> @@ -76,6 +75,14 @@
> 			idesc.id_number = inumber;
> 			switch (inoinfo(inumber)->ino_state) {
>
> +			case FZLINK:
> +			case DZLINK:
> +				if (inoinfo(inumber)->ino_linkcnt == 0) {
> +					clri(&idesc, "UNREF", 1);
> +					break;
> +				}
> +				/* fall through */
> +
> 			case FSTATE:
> 			case DFOUND:
> 				n = inoinfo(inumber)->ino_linkcnt;
> @@ -83,16 +90,6 @@
> 					adjust(&idesc, (short)n);
> 					break;
> 				}
> -				for (zlnp = zlnhead; zlnp; zlnp = zlnp->next) {
> -					if (zlnp->zlncnt == inumber) {
> -						zlnp->zlncnt = zlnhead->zlncnt;
> -						zlnp = zlnhead;
> -						zlnhead = zlnhead->next;
> -						free((char *)zlnp);
> -						clri(&idesc, "UNREF", 1);
> -						break;
> -					}
> -				}
> 				break;
>
> 			case DSTATE:
> Index: sbin/fsck_ffs/pass5.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/fsck_ffs/pass5.c,v
> retrieving revision 1.39
> diff -u -r1.39 pass5.c
> --- sbin/fsck_ffs/pass5.c	9 Apr 2004 19:58:28 -0000	1.39
> +++ sbin/fsck_ffs/pass5.c	6 Sep 2004 00:34:10 -0000
> @@ -216,11 +216,13 @@
> 			case DSTATE:
> 			case DCLEAR:
> 			case DFOUND:
> +			case DZLINK:
> 				newcg->cg_cs.cs_ndir++;
> 				/* FALLTHROUGH */
>
> 			case FSTATE:
> 			case FCLEAR:
> +			case FZLINK:
> 				newcg->cg_cs.cs_nifree--;
> 				setbit(cg_inosused(newcg), i);
> 				break;
>
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----
Marc G. Fournier           Hub.Org Networking Services (http://www.hub.org)
Email: scrappy at hub.org           Yahoo!: yscrappy              ICQ: 7615664


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