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- Add the B_NEEDSGIANT flag which is only set if the vnode that owns a buf

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requires Giant.  It is set in bgetvp and cleared in brelvp.
 - Create QUEUE_DIRTY_GIANT for dirty buffers that require giant.
 - In the buf daemon, only grab giant when processing QUEUE_DIRTY_GIANT and
   only if we think there are buffers in that queue.

Sponsored by:	Isilon Systems, Inc.
This commit is contained in:
jeff 2006-03-31 02:56:30 +00:00
parent 01da4eecd3
commit 2086f279cf
3 changed files with 39 additions and 17 deletions
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51
sys/kern/vfs_bio.c
View File

@ -102,7 +102,7 @@ static void vfs_setdirty(struct buf *bp);
static void vfs_vmio_release(struct buf *bp);
static int vfs_bio_clcheck(struct vnode *vp, int size,
daddr_t lblkno, daddr_t blkno);
static int flushbufqueues(int flushdeps);
static int flushbufqueues(int, int);
static void buf_daemon(void);
static void bremfreel(struct buf *bp);
@ -244,13 +244,14 @@ static struct mtx bpinlock;
/*
* Definitions for the buffer free lists.
*/
#define BUFFER_QUEUES 5 /* number of free buffer queues */
#define BUFFER_QUEUES 6 /* number of free buffer queues */
#define QUEUE_NONE 0 /* on no queue */
#define QUEUE_CLEAN 1 /* non-B_DELWRI buffers */
#define QUEUE_DIRTY 2 /* B_DELWRI buffers */
#define QUEUE_EMPTYKVA 3 /* empty buffer headers w/KVA assignment */
#define QUEUE_EMPTY 4 /* empty buffer headers */
#define QUEUE_DIRTY_GIANT 3 /* B_DELWRI buffers that need giant */
#define QUEUE_EMPTYKVA 4 /* empty buffer headers w/KVA assignment */
#define QUEUE_EMPTY 5 /* empty buffer headers */
/* Queues for free buffers with various properties */
static TAILQ_HEAD(bqueues, buf) bufqueues[BUFFER_QUEUES] = { { 0 } };
@ -1356,6 +1357,8 @@ brelse(struct buf *bp)
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
/* remaining buffers */
} else {
if (bp->b_flags & (B_DELWRI|B_NEEDSGIANT))
bp->b_qindex = QUEUE_DIRTY_GIANT;
if (bp->b_flags & B_DELWRI)
bp->b_qindex = QUEUE_DIRTY;
else
@ -1446,8 +1449,11 @@ bqrelse(struct buf *bp)
panic("bqrelse: free buffer onto another queue???");
/* buffers with stale but valid contents */
if (bp->b_flags & B_DELWRI) {
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
if (bp->b_flags & B_NEEDSGIANT)
bp->b_qindex = QUEUE_DIRTY_GIANT;
else
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_TAIL(&bufqueues[bp->b_qindex], bp, b_freelist);
} else {
/*
* XXX This lock may not be necessary since BKGRDINPROG
@ -2001,7 +2007,6 @@ SYSINIT(bufdaemon, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST, kproc_start, &buf_kp)
static void
buf_daemon()
{
mtx_lock(&Giant);
/*
* This process needs to be suspended prior to shutdown sync.
@ -2027,13 +2032,28 @@ buf_daemon()
* normally would so they can run in parallel with our drain.
*/
while (numdirtybuffers > lodirtybuffers) {
if (flushbufqueues(0) == 0) {
int flushed;
flushed = flushbufqueues(QUEUE_DIRTY, 0);
/* The list empty check here is slightly racy */
if (!TAILQ_EMPTY(&bufqueues[QUEUE_DIRTY_GIANT])) {
mtx_lock(&Giant);
flushed += flushbufqueues(QUEUE_DIRTY_GIANT, 0);
mtx_unlock(&Giant);
}
if (flushed == 0) {
/*
* Could not find any buffers without rollback
* dependencies, so just write the first one
* in the hopes of eventually making progress.
*/
flushbufqueues(1);
flushbufqueues(QUEUE_DIRTY, 1);
if (!TAILQ_EMPTY(
&bufqueues[QUEUE_DIRTY_GIANT])) {
mtx_lock(&Giant);
flushbufqueues(QUEUE_DIRTY_GIANT, 1);
mtx_unlock(&Giant);
}
break;
}
uio_yield();
@ -2081,7 +2101,7 @@ SYSCTL_INT(_vfs, OID_AUTO, flushwithdeps, CTLFLAG_RW, &flushwithdeps,
0, "Number of buffers flushed with dependecies that require rollbacks");
static int
flushbufqueues(int flushdeps)
flushbufqueues(int queue, int flushdeps)
{
struct thread *td = curthread;
struct buf sentinel;
@ -2098,13 +2118,13 @@ flushbufqueues(int flushdeps)
flushed = 0;
bp = NULL;
mtx_lock(&bqlock);
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], &sentinel, b_freelist);
TAILQ_INSERT_TAIL(&bufqueues[queue], &sentinel, b_freelist);
while (flushed != target) {
bp = TAILQ_FIRST(&bufqueues[QUEUE_DIRTY]);
bp = TAILQ_FIRST(&bufqueues[queue]);
if (bp == &sentinel)
break;
TAILQ_REMOVE(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
TAILQ_REMOVE(&bufqueues[queue], bp, b_freelist);
TAILQ_INSERT_TAIL(&bufqueues[queue], bp, b_freelist);
if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL) != 0)
continue;
@ -2170,7 +2190,7 @@ flushbufqueues(int flushdeps)
vn_finished_write(mp);
BUF_UNLOCK(bp);
}
TAILQ_REMOVE(&bufqueues[QUEUE_DIRTY], &sentinel, b_freelist);
TAILQ_REMOVE(&bufqueues[queue], &sentinel, b_freelist);
mtx_unlock(&bqlock);
return (flushed);
}
@ -2575,7 +2595,6 @@ loop:
*/
bp->b_blkno = bp->b_lblkno = blkno;
bp->b_offset = offset;
bgetvp(vp, bp);
BO_UNLOCK(bo);

3
sys/kern/vfs_subr.c
View File

@ -1440,6 +1440,8 @@ bgetvp(struct vnode *vp, struct buf *bp)
ASSERT_VI_LOCKED(vp, "bgetvp");
vholdl(vp);
if (VFS_NEEDSGIANT(vp->v_mount))
bp->b_flags |= B_NEEDSGIANT;
bp->b_vp = vp;
bp->b_bufobj = &vp->v_bufobj;
/*
@ -1477,6 +1479,7 @@ brelvp(struct buf *bp)
syncer_worklist_len--;
mtx_unlock(&sync_mtx);
}
bp->b_flags &= ~B_NEEDSGIANT;
bp->b_vp = NULL;
bp->b_bufobj = NULL;
vdropl(vp);

2
sys/sys/buf.h
View File

@ -216,7 +216,7 @@ struct buf {
#define B_RELBUF 0x00400000 /* Release VMIO buffer. */
#define B_00800000 0x00800000 /* Available flag. */
#define B_01000000 0x01000000 /* Available flag. */
#define B_02000000 0x02000000 /* Available flag. */
#define B_NEEDSGIANT 0x02000000 /* Buffer's vnode needs giant. */
#define B_PAGING 0x04000000 /* volatile paging I/O -- bypass VMIO */
#define B_MANAGED 0x08000000 /* Managed by FS. */
#define B_RAM 0x10000000 /* Read ahead mark (flag) */